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Educators are encouraged to provide inquiry-based, collaborative, and problem solving activities that enhance learning and promote curiosity, skepticism, objectivity, and the use of scientific reasoning. Making anatomical casts or models by injecting solidifying substances into organs is an example of a constructivist activity for achieving these goals. This report describes a student-implemented protocol for making postmortem anatomical casts of the bronchial tree and coronary arteries of rats using Silastic[R] sealant. The teacher facilitated this process by asking leading questions to guide the students toward the development of their own conclusions. This relatively simple and inexpensive procedure has important applications for the constructivist approach to study cardiovascular and respiratory morphology. (Contains 4 figures.)

Many students in general and advanced chemistry courses have difficulty understanding differences in solubility by inspecting changing values of the solubility product constants for sparingly soluble salts. In this demonstration, the concepts involved in understanding the solubility of sparingly soluble salts are illustrated visually. Utilizing bathocuproinedisulfonic acid in a mixed reducing reagent to complex copper(I), we are able to demonstrate to the naked eye copper(I) and copper(II) concentrations resulting from the dissolution of a variety of sparingly soluble copper compounds. The actual concentration of copper in solution can be determined using this visual demonstration in combination with a spectrophotometer. This demonstration visually confirms copper concentrations in the range of 1 x 10[superscript -3] to 1 x 10[superscript -6] M. Calculated solubilities based on a simple algorithm, neglecting secondary equilibria, ion-pair formation, and ionic effects, are in reasonable agreement with the measured solubilities. (Contains 1 table and 1 figure.)

Explains the results of an effort to introduce active learning strategies into the general chemistry curriculum at the United States Naval Academy. Reports that students in an active learning classroom showed significant improvement in performance compared to students in a lecture-based course. (Author/YDS)

Medieval composers and audiences alike took great stock in the cultural value of auctoritas, the notion that new compositions should closely follow the patterns set by previously accepted authors. The present study examines the concept as it applies to the composition of a particular manuscript: Paris, BnF fr. 12615. The codex underwent at least two, and most likely three, stages of compilation. Strategies of compilatio and ordinatio are examined to demonstrate how the compiler uses earlier songbooks dedicated to Thibaut de Champagne (d. 1253) to shape his own songbook and gradually move his anthology from aristocratic to urban, Artesian notions of auctoritas. Subsequent additions to 12615 enhance the original compilers scheme., MMEDIEVAL AUDIENCES DID NOT APPRECIATE SUDDEN CHANGES IN aesthetic taste. On the contrary, they expected to recognize most of what they heard, delighted in borrowings, parodies, and allusions, and admired [...]

CARAPEZZA, Francesco. Ecdotica galloromanza negli Stati Uniti d'America. Atti della Accademia Nazionale dei Lincei. Memorie IX.xix fasc. 4. Roma: Bardi Editore, 2005. ISSN 0391-8149. ISBN 88-218-0942-0. In a field like [...]

Chemiluminescence (CL) of acridinium esters (AE) has found widespread use in analytical chemistry. Using the mechanism of the reaction of [H.sub.2][O.sub.2] with 10-methyl-9-(p-formylphenyl)acridinium carboxylate trifluoromethane-sulfonate and a modified flow injection system, the reaction rates of each step in the mechanism were evaluated and used in a kinetic model to optimize the analysis of [H.sub.2][O.sub.2]. Operational parameters for a flow injection analysis system (reagent pH, flow rate, sample volume, PMT settings) were optimized using the kinetic model. The system is most sensitive to reaction pH due to competition between AE hydrolysis and CL. The optimized system was used to determine [H.sub.2][O.sub.2] concentrations in natural waters, including rain, freshwater, and seawater. The lower limit of detection varied in natural waters, from 352 pM in open ocean seawater (mean, 779 pM [+ or -] 15.0%, RSD) to 58.1 nM in rain (mean, 6,340 nM [+ or -] 0.92%, RSD). The analysis is specific for [H.sub.2][O.sub.2] and is therefore of potential interest for atmospheric chemistry applications where organoperoxides have been reported in the presence of [H.sub.2][O.sub.2].

Certain strains of Lactococcus lactis produce the broad-spectrum bacteriocin nisin, which belongs to the lantibiotic class of antimicrobial peptides. The genes encoding nisin are organized in three contiguous operons: nisABTCIP, encoding production and immunity (nisI); nisRK, encoding regulation; and nisFEG, also involved in immunity. Transcription of nisABTCIP and nisFEG requires autoinduction by external nisin via signal transducing by NisRK. This organization poses the intriguing question of how sufficient immunity (NisI) can be expressed when the nisin cluster enters a new cell, before it encounters external nisin. In this study, Northern analysis in both Lactococcus and Enterococcus backgrounds revealed that nisI mRNA was present under conditions when no nisA transcription was occurring, suggesting an internal promoter within the operon. The nisA transcript was significantly more stable than nisI, further substantiating this. Reverse transcriptase PCR analysis revealed that the transcription initiated just upstream from nisI. Fusing this region to a lacZ gene in a promoter probe vector demonstrated that a promoter was present. The transcription start site (TSS) of the nisI promoter was mapped at bp 123 upstream of the nisI translation start codon. Ordered 5' deletions revealed that transcription activation depended on sequences located up to bp -234 from the TSS. The presence of poly(A) tracts and computerized predictions for this region suggested that a high degree of curvature may be required for transcription initiation. The existence of this nisI promoter is likely an evolutionary adaptation of the nisin gene cluster to enable its successful establishment in other cells following horizontal transfer.

The native lactococcal plasmid, pKR223, from Lactococcus lactis subsp, lactis biovar diacetylactis KR2 encodes two distinct bacteriophage-resistant mechanisms, the LlaKR2I restriction and modification (R/M) system and the abortive infection (Abi) mechanism, AbiR, that impedes bacteriophage DNA replication. This study completed the characterization of AbiR, revealing that it is the first Abi system to be encoded by three genes, abiRa, abiRb, and abiRc, arranged in an operon and that it requires the methylase gene from the LlaKR2I R/M system. An analysis of deletion and insertion clones demonstrated that the AbiR operon was toxic in L. lactis without the presence of the LlaKR2I methylase, which is required to protect L. lactis from AbiR toxicity. The novelty of the AbiR system resides in its original gene organization and the unusual protective role of the LlaKR2I methylase. Interestingly, the AbiR genetic determinants are flanked by two IS982 elements generating a likely transposable AbiR composite. This observation not only substantiated the novel function of the LlaKR2I methylase in the AbiR system but also illustrated the evolution of the LlaKR2I methylase toward a new and separate cellular function. This unique structure of both the LlaKR2I R/M system and the AbiR system may have contributed to the evolution of the LlaKR21 methylase toward a novel role comparable to that of the cell cycle-regulated methylases that include Dam and CcrM methylases. This new role for the LIaKR2I methylase offers a unique snapshot into the evolution of the cell cycle-regulated methylases from an existing R/M system.

Three prophage-like elements those are present in the genomes of bifidobacterium breve UCC 2003 (Bbr-1), Bifidobacterium longum NCC 2705 (Bl-1), and Bifidobacterium longum DJO10A (Blj-1) are analyzed. The comparison of these prophage sequences with those available in the public databases shows that the bidifobacterial prophages possess a typical mosaic genome structure.

Research has been conducted on the native lactococcal plasmid pKR223. Results indicate that this plasmid encodes abortive infection mechanism that affects prolate-headed-phage proliferation.

A single, triplicate arbitrarily primed (AP)-PCR procedure for molecular fingerprinting of lactic acid bacteria has been developed. It is known that AP-PCR can be used to generate characteristic DNA fingerprint patterns but small changes in reaction conditions can bring band irreproducibility. One method that takes in triplicate reactions intentionally exposed to three annealing temperatures made bands reproducibly generated to be recognized possible. This was used to fingerprint representative isolates from the major genera of lactic acid bacteria and Bifidobacterium to the strain level.