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U.S. schools are facing a crisis of leadership because many school districts are finding it increasingly difficult to recruit new principals. Whereas teachers represent the group from which the largest number of new principals is likely to be drawn, fewer and fewer of them now seem willing to seek administrative positions. Understanding their perspectives provides an important basis for addressing critical shortages. Using survey data from a large Ohio sample, the present study examined the views of teachers with regard to what are commonly perceived as incentives and disincentives associated with the principalship. It also explored the characteristics of teachers that make them more and less receptive to the idea of seeking leadership positions. Results showed that, in general, teachers view the disincentives associated with the principalship as more potent than the incentives. Variables that were significantly associated with the view that the principalship was “worth it” (i.e., that the incentives outweighed the disincentives) included gender (i.e., maleness), administrative licensure, and the tendency to value the practice whereby school leaders groom teachers for leadership positions.

An efficient gene transfer can be achieved in mouse liver by a rapid tail vein injection of a large volume of plasmid DNA solution (hydrodynamics-based transfection). The mechanism of gene transfer by this procedure is not known. It must be related to the uptake and intracellular fate of DNA. We have investigated the problem by following the uptake by mouse liver and the intracellular distribution of DNA after a rapid tail vein injection of a large (2.0 ml) or a small (0.2 ml) volume of ³⁵S-DNA solution. Total and acid-soluble radioactivity were measured in liver homogenates at increasing times after injection, and their subcellular distributions were established by centrifugation methods and compared with the distributions of marker enzymes of the membrane compartments involved in endocytosis: alkaline phosphodiesterase (plasma membrane) and cathepsin C (lysosomes). ³⁵S-DNA uptake by the liver is similar when a small or a large volume of injection is used but its degradation is markedly slower after a 2.0 ml injection. When a small volume of injection is given, distribution of radioactivity after differential centrifugation indicates that the plasmid DNA is endocytosed and reaches lysosomes where it is hydrolysed. After a large volume injection, part of ³⁵S-DNA has the same fate, another part remains acid-precipitable for at least 1 h and is associated with structures sedimenting at low centrifugation speed in the nuclear fraction N. Analysis of that fraction by gradient centrifugation suggests that these structures are plasma membrane fragments that could originate from the apical domain of hepatocytes. The proportion of ³⁵S-DNA associated with hepatocytes is about doubled after a large volume injection. Fractionation of isolated hepatocytes by centrifugation confirms results obtained on the whole liver. Treatment of the N fraction or isolated hepatocytes with pancreatic DNAse illustrates that ³⁵S-DNA that remains bound to plasma membrane after a large volume injection is located on the outer face. The fact that after an hydrodynamic injection ³⁵S-DNA remains bound to the outside face of the plasma membrane for at least 1 h indicates that it is not, or very slowly, internalised during that period. The relatively small difference in the amount of DNA picked up by hepatocytes depending on the type of injection could not explain the absence of expression after a conventional injection and the strong expression after a hydrodynamic injection. If DNA enters the cells by endocytosis, even after an hydrodynamic injection, its persistence at the outside face of the plasma membrane could favour transfection by allowing hepatocytes to dispose for a relatively long time of a reservoir of intact DNA. Copyright © 2002 John Wiley & Sons, Ltd.

In previous work, zein was plasticized with oleic acid to obtain flexible films. However, it was observed that film properties were affected by the preparation method employed. Our objective was to investigate the effect of processing methods on thermal behavior of zein films by differential scanning calorimetry (DSC). Films containing 41% oleic acid were prepared by casting ethanol solutions of its components on flat surfaces or by extrusion of zein resins prepared by cold water precipitation of ethanol solutions of zein and oleic acid. Extrusion was carried out in single-screw or twin-screw extruders. Zein films were finished by hot rolling or heated in a Carver press. DSC thermograms showed large oleic acid melting peaks for cast films, smaller peaks for resin films, and no apparent peaks for heat-treated samples. It was suggested that the resin formation process enhanced zein-oleic acid interactions and promoted plasticization. All samples showed glass transitions at low temperatures.

AbstractTwo new species are described and illustrated: Fusarium brevicatenulatumisolated from the noxious witchweed (Striga asiatica) in Madagascar, and F. pseudoanthophilumisolated from Zea maysin Zimbabwe. F. brevicatenulatumis characterized by long-oval to obovoid, mostly 0-septate conidia adhering usually in false heads on mostly monophialidic conidiophores in the aerial mycelium, the formation of very short false chains of conidia under continuous black light, the rare production of 3-septate sporodochial conidia, and the absence of chlamydospores; F. pseudoanthophilumby the production of mostly 0-septate, obovoid to davate and some pyriform conidia that adhere in false heads and sometimes in very short chains on conidiophores of the aerial mycelium that are often branched and polyphialidic, by 3–5-septate sporodochial conidia, and by chains of chlamydospores.