Ten tips to encourage student interaction with screen-capture type vodcasts

Video podcasts (vodcasts) are gaining popularity in medical education, but they can be a passive learning modality if students do not actively engage with the content. Of the two categories of vodcast software, screen-capture (mp4 output) and Flash™ (HTML5/Flash output), screen-capture has greater potential to result in passive learning because students cannot physically interact with the content. However, screen-capture offers several advantages for the producer (often faculty) and the consumer (students). As such, this type of software is popular with medical school faculty. To encourage active learning, ten tips are presented with specific strategies that faculty can use with screen-capture type vodcasts. Many of the tips also apply to Flash-type vodcasts. By incorporating these strategies, faculty with limited technical abilities can create engaging vodcasts that stimulate active learning.

Tracking Active Learning in the Medical School Curriculum: A Learning-Centered Approach

BACKGROUND

Medical education is moving toward active learning during large group lecture sessions. This study investigated the saturation and breadth of active learning techniques implemented in first year medical school large group sessions.

METHODS

Data collection involved retrospective curriculum review and semistructured interviews with 20 faculty. The authors piloted a taxonomy of active learning techniques and mapped learning techniques to attributes of learning-centered instruction.

RESULTS

Faculty implemented 25 different active learning techniques over the course of 9 first year courses. Of 646 hours of large group instruction, 476 (74%) involved at least 1 active learning component.

CONCLUSIONS

The frequency and variety of active learning components integrated throughout the year 1 curriculum reflect faculty familiarity with active learning methods and their support of an active learning culture. This project has sparked reflection on teaching practices and facilitated an evolution from teacher-centered to learning-centered instruction.

A descriptive, cross-sectional study of medical student preferences for vodcast design, format and pedagogical approach

BACKGROUND

Vodcasts (video podcasts) are becoming increasingly popular in medical education. At A.T. Still University School of Osteopathic Medicine in Arizona (ATSU SOMA), vodcasts are an essential component of our blended learning environment, where year 2-4 students train in a contextual setting at community health centers across the U.S. Vodcasts are used far less frequently in our year 1 residential learning environment at the main campus in Arizona, but we are considering moving to significantly more interactive educational experiences with on-demand videos followed by in-class activities. The aim of this study was to determine stakeholder (i.e. medical student) preferences for vodcast design, format, and pedagogical strategies. The overall goal was to increase opportunities for students to learn with this modality.

METHODS

An interactive Qualtrics™ survey was administered to three cohorts of medical students. The survey generated quantitative and open-ended response data that addressed principles of vodcast instructional design and learning. Responses to survey items were analyzed for statistical significance using the independent samples t-test for interval data, the chi-square test for categorical data, and the Kruskal-Wallis test for ordinal data, using the post-hoc Bonferroni procedure to determine the appropriate α level. Responses to open-ended prompts were categorized using open- and axial-coding.

RESULTS

The most highly valued vodcast attributes, considered essential by all three cohorts, were clear explanations, organization, conciseness, high-yield for medical board exams, and the ability to speed vodcasts up. The least helpful vodcast attributes for all three cohorts were music and objects moving on screen. The average preferred vodcast length for each cohort was 27-28 min. There were significant differences between the less experienced learners in the residential setting and the more mature learners in the blended learning environment regarding certain vodcast attribute preferences, format of included practice questions, explanations for preferred vodcast lengths, and reasons for not viewing vodcasts.

CONCLUSIONS

Overall, learner preferences were in line with non-interactive, screen-capture type vodcasts, which have lower demands on institutional cost and faculty production time than Flash™-type interactive vodcasts. Students in the blended learning environment were much more focused on vodcast features that decreased their time commitment, including a preference for noninteractive vodcasts. Given the increase in distance learning in medical education, our results should be of value to other medical programs.

What millennial medical students say about flipped learning

Flipped instruction is gaining popularity in medical schools, but there are unanswered questions such as the optimum amount of the curriculum to flip and whether flipped sessions should be mandatory. We were in a unique position to evaluate feedback from first-year medical students who had experienced both flipped and lecture-based courses during their first semester of medical school. A key finding was that the students preferred a variety of different learning formats over an "all or nothing" learning format. Learning format preferences did not necessarily align with perceptions of which format led to better course exam performance. Nearly 70% of respondents wanted to make their own decisions regarding attendance. Candid responses to open-ended survey prompts reflected millennial preferences for choice, flexibility, efficiency, and the ability to control the pace of their learning, providing insight to guide curricular improvements.

Developing technology-enhanced active learning for medical education: challenges, solutions, and future directions

Growing up in an era of video games and Web-based applications has primed current medical students to expect rapid, interactive feedback. To address this need, the A.T. Still University-School of Osteopathic Medicine in Arizona (Mesa) has developed and integrated a variety of approaches using technology-enhanced active learning for medical education (TEAL-MEd) into its curriculum. Over the course of 3 years (2010-2013), the authors facilitated more than 80 implementations of games and virtual patient simulations into the education of 550 osteopathic medical students. The authors report on 4 key aspects of the TEAL-MEd initiative, including purpose, portfolio of tools, progress to date regarding challenges and solutions, and future directions. Lessons learned may be of benefit to medical educators at academic and clinical training sites who wish to implement TEAL-MEd activities.

Evaluating medical student engagement during virtual patient simulations: a sequential, mixed methods study

BACKGROUND

Student engagement is an important domain for medical education, however, it is difficult to quantify. The goal of this study was to investigate the utility of virtual patient simulations (VPS) for increasing medical student engagement. Our aims were specifically to investigate how and to what extent the VPS foster student engagement. This study took place at A.T. Still University School of Osteopathic Medicine in Arizona (ATSU-SOMA), in the USA.

METHODS

First year medical students (n = 108) worked in teams to complete a series of four in-class virtual patient case studies. Student engagement was measured, defined as flow, interest, and relevance. These dimensions were measured using four data collection instruments: researcher observations, classroom photographs, tutor feedback, and an electronic exit survey. Qualitative data were analyzed using a grounded theory approach.

RESULTS

Triangulation of findings between the four data sources indicate that VPS foster engagement in three facets: 1) Flow. In general, students enjoyed the activities, and were absorbed in the task at hand. 2) Interest. Students demonstrated interest in the activities, as evidenced by enjoyment, active discussion, and humor. Students remarked upon elements that caused cognitive dissonance: excessive text and classroom noise generated by multi-media and peer conversations. 3) Relevance. VPS were relevant, in terms of situational clinical practice, exam preparation, and obtaining concrete feedback on clinical decisions.

CONCLUSIONS

Researchers successfully introduced a new learning platform into the medical school curriculum. The data collected during this study were also used to improve new learning modules and techniques associated with implementing them in the classroom. Results of this study assert that virtual patient simulations foster engagement in terms of flow, relevance, and interest.

Student perceptions of gamified audience response system interactions in large group lectures and via lecture capture technology

BACKGROUND

Higher education students have positive attitudes about the use of audience response systems (ARS), but even technology-enhanced lessons can become tiresome if the pedagogical approach is exactly the same with each implementation. Gamification is the notion that gaming mechanics can be applied to routine activities. In this study, TurningPoint (TP) ARS interactions were gamified and implemented in 22 large group medical microbiology lectures throughout an integrated year 1 osteopathic medical school curriculum.

METHODS

A 32-item questionnaire was used to measure students' perceptions of the gamified TP interactions at the end of their first year. The survey instrument generated both Likert scale and open-ended response data that addressed game design and variety, engagement and learning features, use of TP questions after class, and any value of lecture capture technology for reviewing these interactive presentations. The Chi Square Test was used to analyze grouped responses to Likert scale questions. Responses to open-ended prompts were categorized using open-coding.

RESULTS

Ninety-one students out of 106 (86 %) responded to the survey. A significant majority of the respondents agreed or strongly agreed that the games were engaging, and an effective learning tool. The questionnaire investigated the degree to which specific features of these interactions were engaging (nine items) and promoted learning (seven items). The most highly ranked engagement aspects were peer competition and focus on the activity (tied for highest ranking), and the most highly ranked learning aspect was applying theoretical knowledge to clinical scenarios. Another notable item was the variety of interactions, which ranked in the top three in both the engagement and learning categories. Open-ended comments shed light on how students use TP questions for exam preparation, and revealed engaging and non-engaging attributes of these interactive sessions for students who review them via lecture capture.

CONCLUSIONS

Students clearly valued the engagement and learning aspects of gamified TP interactions. The overwhelming majority of students surveyed in this study were engaged by the variety of TP games, and gained an interest in microbiology. The methods described in this study may be useful for other educators wishing to expand the utility of ARS in their classrooms.

Antineoplastic agents 596. Isolation and structure of chromomycin A5 from a Beaufort Sea microorganism

Isolation and structure of chromomycin A₅ from a Beaufort Sea microorganism.

Mapping of Medical Microbiology Content in a Clinical Presentation Curriculum

Clinically important microbes, and the pathogenesis, symptoms and diagnosis of their corresponding infectious diseases were integrated into clinical schemes within a clinical presentation curriculum. Decisions on microbe placement considered a variety of factors, including spaced reinforcement of major pathogens. We report here the map of our integrated medical microbiology curriculum.

Isolation and structures of axistatins 1-3 from the Republic of Palau marine sponge Agelas axifera Hentschel

An investigation begun in 1979 directed at the Republic of Palau marine sponge Agelas axifera Hentschel for cancer cell growth inhibitory constituents subsequently led to the isolation of three new pyrimidine diterpenes designated axistatins 1 (1), 2 (2), and 3 (3), together with the previously reported formamides 4, 5, and agelasine F (6). The structures were elucidated by analysis of 2D-NMR spectra and by HRMS. All of the isolated compounds were found to be moderate inhibitors of cancer cell growth. Axistatins 1-3 (1-3), formamide 4, and agelasine F (6) also exhibited antimicrobial activity.

Antineoplastic agents. 548. Synthesis of iodo- and diiodocombstatin phosphate prodrugs

Toward the objective of designing a structurally modified analogue of the combretastatin A-4 phosphate prodrug (1b) with the potential for increased specificity toward thyroid carcinoma, synthesis of a series of iodocombstatin phosphate (11a-h) and diiodocombstatin phosphate prodrugs (12a-h) has been accomplished. The diiodo series was obtained via 8a and 9c from condensation of 4 and 6, and the iodo sequence involved a parallel pathway. Both series of iodocombstatins were found to display significant to powerful inhibition of the growth of a panel of human cancer cell lines and of the murine P388 lymphocytic leukemia cell line. Of the diiodo series, 12a was also found to markedly inhibit growth of pediatric neuroblastoma, and monoiodocombstatin 9a strongly inhibited HUVEC growth. Overall, the strongest activity was found against the breast, CNS, leukemia, lung, and prostate cancer cell lines and the least activity against the pancreas and colon lines. Parallel biological investigations of tubulin interaction, antiangiogenesis, and antimicrobial effects were also conducted.

The cephalostatins. 21. Synthesis of bis-steroidal pyrazine rhamnosides (1)

The synthesis of bis-steroidal pyrazines derived from 3-oxo-11,21-dihydroxypregna-4,17(20)-diene (4) and glycosylation of a D-ring side chain with α-L-rhamnose have been summarized. Rearrangement of steroidal pyrazine 10 to 14 was found to occur with boron triflouride etherate. Glycosylation of pyrazine 10 using 2,3,4-tri-O-acetyl-α-L-rhamnose iodide led to 1,2-orthoester-α-L-rhamnose pyrazine 17b. By use of a persilylated α-L-rhamnose iodide as donor, formation of the orthoester was avoided. Bis-steroidal pyrazine 10 and rhamnosides 17b and 21c were found to significantly inhibit cancer cell growth in a murine and human cancer cell line panel. Pyrazine 9 inhibited growth of the nosocomial pathogen Enterococcus faecalis.

Culturability and secondary metabolite diversity of extreme microbes: expanding contribution of deep sea and deep-sea vent microbes to natural product discovery

Microbes from extreme environments do not necessarily require extreme culture conditions. Perhaps the most extreme environments known, deep-sea hydrothermal vent sites, support an incredible array of archaea, bacteria, and fungi, many of which have now been cultured. Microbes cultured from extreme environments have not disappointed in the natural products arena; diverse bioactive secondary metabolites have been isolated from cultured extreme-tolerant microbes, extremophiles, and deep-sea microbes. The contribution of vent microbes to our arsenal of natural products will likely grow, given the culturability of vent microbes; their metabolic, physiologic, and phylogenetic diversity; numerous reports of bioactive natural products from microbes inhabiting high acid, high temperature, or high pressure environments; and the recent isolation of new chroman derivatives and siderophores from deep-sea hydrothermal vent bacteria.

Temperature affects the susceptibility of Cryptococcus neoformans biofilms to antifungal agents

The fungal opportunist Cryptococcus neoformans forms biofilms in vitro and in vivo. C. neoformans has an unusual ability to grow over a wide range of temperatures, and is one of only two species in the genus able to grow at 37 degrees C. The optimum growth temperature in the laboratory is 30 degrees C, but Clinical and Laboratory Standards Institute (CLSI) planktonic susceptibility testing is performed at 35 degrees C. We investigated whether these growth temperatures affected C. neoformans biofilm formation and drug resistance. Biofilms of 30 strains of C. neoformans were grown at 30 degrees C or 35 degrees C, and antifungal susceptibilities evaluated at 30 degrees C or 35 degrees C using minimum biofilm eradication endpoints. At 35 degrees C, biofilms from 40% of the strains were more susceptible to flucytosine, 30% were more susceptible to nystatin, 27% were more susceptible to amphotericin, and 20% were more susceptible to fluconazole, as compared to 30 degrees C. The reverse, that is an increased susceptibility at 30 degrees C, only occurred with a single strain using nystatin or fluconazole. For the remaining strains, biofilm susceptibility was equivalent at the two temperatures. Biofilm colony forming units (CFU)s, as measured indirectly by 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) reduction, were greater at 35 degrees C than at 30 degrees C for the majority of the strains. Thus, growth temperature does affect C. neoformans biofilm properties, but factors other than relative biofilm CFUs/ml must be involved in the increased drug susceptibility at 35 degrees C.

Small-molecule elicitation of microbial secondary metabolites

Microbial natural products continue to be an unparalleled resource for pharmaceutical lead discovery, but the rediscovery rate is high. Bacterial and fungal sequencing studies indicate that the biosynthetic potential of many strains is much greater than that observed by fermentation. Prodding the expression of such silent (cryptic) pathways will allow us to maximize the chemical diversity available from microorganisms. Cryptic metabolic pathways can be accessed in the laboratory using molecular or cultivation‐based approaches. A targeted approach related to cultivation‐based methods is the application of small‐molecule elicitors to specifically affect transcription of secondary metabolite gene clusters. With the isolation of the novel secondary metabolites lunalides A and B, oxylipins, cladochromes F and G, nygerone A, chaetoglobosin‐542, ‐540 and ‐510, sphaerolone, dihydrosphaerolone, mutolide and pestalone, and the enhanced production of known secondary metabolites like penicillin and bacitracin, chemical elicitation is proving to be an effective way to augment natural product libraries.

Antineoplastic agents 582. Part 1: Isolation and structure of a cyclobutane-type sesquiterpene cancer cell growth inhibitor from Coprinus cinereus (Coprinaceae)

Bioassay-guided (murine P388 lymphocytic leukemia and human cancer cell lines) separation of an ethyl acetate extract prepared from the inky cap fungus Coprinus cinereus led to the isolation of three new sesquiterpenes, 7,7a-diepicoprinastatin 1 (1), 14-hydroxy-5-desoxy-2S,3S,9R-illudosin (2), and 4,5-dehydro-5-deoxyarmillol (3), together with the known armillol (4). The structure and relative configuration of 1 was determined by single-crystal X-ray diffraction experiments. The structures of compounds 2, 3, and 4 were each deduced by a combination of HRMS and 1D and 2D NMR techniques. Cyclobutane 2 led to modest inhibition of the murine P388 leukemia cell line.

Antineoplastic agents. 556. Isolation and structure of Coprinastatin 1 from Coprinus cinereus

Cancer cell line bioassay-guided separation of an ethyl acetate extract prepared from a plant-associated fungus, Coprinus cinereus, led to the isolation of three new sesquiterpenes, coprinastatin 1 (1), coprinol (2), and the epimer (4a), of the known sesquiterpene triol (4b). The previously described sesquiterpene 3 and oxazolinone 5 were also isolated. The structure and relative configuration of coprinastatin 1 (1) were determined by HRMS and by 1D- and 2D-NMR spectroscopic analyses. The structure of terpene 2 was elucidated by single-crystal X-ray diffraction experiments. The remaining structures were similarly determined, structure 3 by spectroscopic analyses and both 4a and 5 by X-ray crystal structure determination. Coprinastatin 1 (1) was found to inhibit growth of the murine P388 lymphocytic leukemia cell line and the pathogenic bacterium Neisseria gonorrhoeae.

Isolation of human cancer cell growth inhibitory, antimicrobial lateritin from a mixed fungal culture

The purpose of this study was to attempt the reproducible coculture of more than two fungi for biosynthesis of potential antineoplastic substances. Five different fungi were simultaneously inoculated into broth cultures and grown for two weeks. Cancer cell line bioassay-guided fractionation, NMR, and mass spectroscopy led to the isolation and characterization of lateritin. Lateritin inhibited the growth of a mini-panel of human cancer cell lines, gram-positive bacteria, and Candida albicans. Individually, the five fungi did not synthesize detectable levels of lateritin. This study adds to the small but growing body of evidence that mixed fermentation is a viable avenue for natural product drug discovery. In addition, this is the first report of the reproducible coculture of more than two microbes for natural product biosynthesis, and the first report of the human solid tumor cell line and antimicrobial activities of lateritin.

Antineoplastic agents. 573. isolation and structure of papilistatin from the papilionid butterfly Byasa polyeuctes termessa

Bioassay-guided separation of an extract of the wings from a Taiwan butterfly, Byasa polyeuctes termessa, allowed isolation of a new cancer cell growth inhibitor designated papilistatin (1a). The structure was determined by analysis of 1D and 2D NMR spectra and by HRMS. Against a panel of six human and the murine P388 leukemia cancer cell lines, papilistatin exhibited cancer cell growth inhibition with GI(50)'s of 0.093-3.5 microg/mL. Papilistatin was also found to have antibacterial activity.

Application of a high throughput Alamar blue biofilm susceptibility assay to Staphylococcus aureus biofilms

Background

Staphylococcus aureus and S. epidermidis biofilms differ in structure, growth and regulation, and thus the high-throughput method of evaluating biofilm susceptibility that has been published for S. epidermidis cannot be applied to S. aureus without first evaluating the assay's reproducibility and reliability with S. aureus biofilms.

Methods

Staphylococcus aureus biofilms were treated with eleven approved antibiotics, lysostaphin, or Conflikt^®, exposed to the oxidation reduction indicator Alamar blue, and reduction relative to untreated controls was determined visually and spectrophotometrically. The minimum biofilm inhibitory concentration (MBIC) was defined as ≤ 50% Alamar blue reduction and a purple/blue well 60 min after the addition of Alamar blue. Because all of the approved antibiotics had MBICs >128 μg/ml (most >2048 μg/ml), lysostaphin and Conflikt^®, with relatively low MBICs, were used to correlate Alamar blue reduction with 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) reduction and viable counts (CFU/ml) for S. aureus ATCC 29213 and three clinical isolates. Alamar blue's stability and lack of toxicity allowed CFU/ml to be determined from the same wells as Alamar blue absorbances.

Results

Overall, Alamar blue reduction had excellent correlation with XTT reduction and with CFU/ml. For ATCC 29213 and two clinical isolates treated with lysostaphin or Conflikt^®, Alamar blue reduction had excellent correlation with XTT reduction (r = 0.93-0.99) and with CFU/ml (r = 0.92-0.98). For one of the clinical isolates, the results were moderately correlated for Conflikt^® (r = 0.76, Alamar blue vs. XTT; r = 0.81, Alamar blue vs. CFU/ml) and had excellent correlation for lysostaphin (r = 0.95, Alamar blue vs. XTT; r = 0.97, Alamar blue vs. CFU/ml).

Conclusion

A reliable, reproducible method for evaluating biofilm susceptibility was successfully applied to S. aureus biofilms. The described method provides researchers with a simple, nontoxic, relatively inexpensive, high throughput measure of viability after drug treatment. A standardized biofilm Alamar blue assay should greatly increase the rate of discovery of S. aureus biofilm specific agents.

In vivo activity of anprocide alone, and in vitro activity in combination with conventional antibiotics against Staphylococcus aureus and Staphylococcus epidermidis biofilms

The alarming spread of multiple drug resistance in Staphylococcus aureus, combined with the frequent occurrence of S. aureus and Staphylococcus epidermidis in biofilm-type infections, indicates a growing need for new therapies. The experimental steroidal amide anprocide [3beta-acetoxy-17beta-(l-prolyl)amino-5alpha-androstane] significantly reduced c.f.u. ml(-1) per suture (P <0.0001) in a murine model of topical S. aureus infection. In chequerboard assays with planktonic-grown S. aureus and S. epidermidis, anprocide was synergistic with bacitracin, oxacillin, clindamycin or ceftriaxone. Anprocide was also synergistic in combination with bacitracin or oxacillin against some isolates of biofilm-grown S. aureus and S. epidermidis.

Antineoplastic agents. 570. Isolation and structure elucidation of bacillistatins 1 and 2 from a marine Bacillus silvestris

Two new cyclodepsipeptides designated bacillistatins 1 (1) and 2 (2) have been isolated from cultures of a sample of Bacillus silvestris that was obtained from a Pacific Ocean (southern Chile) crab. Each 12-unit cyclodepsipeptide strongly inhibited growth of a human cancer cell line panel, with GI(50)'s of 10(-4)-10(-5) microg/mL, and each compound was active against antibiotic-resistant Streptococcus pneumoniae. The structures were elucidated by a combination of X-ray diffraction and mass and 2D NMR spectroscopic analyses, together with chemical degradation.

Mixed fermentation for natural product drug discovery

Natural products continue to play a major role in drug discovery and development. However, chemical redundancy is an ongoing problem. Genomic studies indicate that certain groups of bacteria and fungi have dozens of secondary metabolite pathways that are not expressed under standard laboratory growth conditions. One approach to more fully access the metabolic potential of cultivatable microbes is mixed fermentation, where the presence of neighboring microbes may induce secondary metabolite synthesis. Research to date indicates that mixed fermentation can result in increased antibiotic activity in crude extracts, increased yields of previously described metabolites, increased yields of previously undetected metabolites, analogues of known metabolites resulting from combined pathways and, importantly, induction of previously unexpressed pathways for bioactive constituents.

Antineoplastic agents. 536. New sources of naturally occurring cancer cell growth inhibitors from marine organisms, terrestrial plants, and microorganisms(1a,)

Bioassay-guided fractionation of extracts of various plants, marine organisms, and microorganisms has led to the discovery of new natural sources of a number of known compounds that have significant biological activity. The isolation of interesting and valuable cancer cell growth inhibitors including majusculamide C ( 1), axinastatin 5 ( 5), bengazoles A ( 6), B ( 7), and E ( 8), manzamine A ( 10), jaspamide ( 11), and neoechinulin A ( 19) has been summarized.

Microplate Alamar blue assay for susceptibility testing of Candida albicans biofilms

Although biofilm-based fungal infections are an important cause of morbidity and mortality in patients, there is no standardized method for the in vitro evaluation of the drug susceptibility of biofilms. We investigated a high-throughput method for determining the susceptibility of Candida albicans biofilms that uses the oxidation reduction indicator Alamar blue (AB). Biofilms from the tested Candida albicans strains were markedly resistant to amphotericin B (AMB), nystatin (NYT), fluconazole (FLC) and 5-fluorouracil (5FC), but susceptible to Conflikt disinfectant. The latter was used in comparative studies of AB reduction with two other methods for assessing in vitro drug susceptibility i.e., 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) reduction and enumeration of viable colony counts (CFU/ml). AB results correlated well with XTT (r=0.88-0.93) and CFU/ml (r=0.93-0.99) for all four C. albicans test strains. This simple, reproducible method for determining in vitro drug susceptibility should facilitate discovery of antifungals active against Candida biofilms.

Antineoplastic agents. 560. Isolation and structure of kitastatin 1 from an Alaskan Kitasatospora sp

By utilizing a bioassay-guided separation (P388 lymphocytic leukemia and a panel of human cancer cell lines) of fermentation broths from a Kitasatospora sp. collected from a tundra soil sample taken at the shore of the Beaufort Sea, we have isolated three powerful (GI50 to 0.0006 microg/mL) cancer cell growth inhibitors (1-3) and determined their structures to be closely related cyclodepsipeptides. From 380 L fermentations of Kitasatospora sp. were obtained 2.6 mg of a new cyclodepsipeptide designated kitastatin 1 (3), accompanied by the previously known respirantin (1, 10.8 mg) and its valeryl homologue (2, 4.8 mg). The structures were determined by employment of a series of high-resolution mass and 2D NMR spectroscopic analyses. The stereochemical assignments and overall structures were confirmed by subsequent total synthesis of depsipeptide 1, as reported in the accompanying contribution.

Antineoplastic agents. 561. Total synthesis of respirantin

Total synthesis of the 18-membered ring cyclodepsipeptide believed to be respirantin (1b) has been achieved. The key step in the synthesis is an intramolecular transesterification of the beta-ketoester alcohol 6 to afford the protected macrocycle 5. The synthetic product was shown to be identical to a natural product presumed to be respirantin (1b), and the absolute stereochemistry of six of the seven asymmetric centers of cyclodepsipeptide 1b was unequivocally established. Respirantin (1b) was found to be a remarkable inhibitor of cancer cell growth and related to the antimycin family of antibiotics.

Antineoplastic Agents. 554. The manitoba bacterium Streptomyces sp

A Streptomyces sp. isolated from riverbank soil in Manitoba, Canada, was found to contain two cancer cell growth inhibitories: diazaanthraquinone 1 and 3-(hydroxyacetyl)indole (8). The structures were determined by interpretation of data from HRMS, UV, and high-field (400 MHz) NMR experiments. The red-colored diazaanthraquinone 1 and 3-(hydroxyacetyl)indole (8) were found to inhibit (0.1-3 microg/mL) growth of a minipanel of human cancer cell lines and P388 lymphocytic leukemia cells. Diazaanthraquinone 1 was also found to inhibit growth of the bacteria Streptococcus pneumoniae and Neisseria gonorrheae. However, three companion constituents, cyclo-Pro-Leu (5), cyclo-Pro-Phe (6), and cyclo-Pro-Val (7), did not inhibit cancer cell growth.

In vitro and in vivo antifungal activities of the marine sponge constituent spongistatin

Spongistatin 1 is a macrocyclic lactone polyether from the marine sponge Hyrtios erecta. The aim of this study was to evaluate the in vitro and in vivo antifungal efficacies and mechanism of spongistatin 1. Spongistatin 1 was fungicidal for the majority of 74 reference strains and clinical isolates, including those resistant to flucytosine, ketoconazole or fluconazole, and retained activity in the presence of human serum or at lowered pH. The duration of the postantifungal effect following 1 h exposure to one, four and eight times the minimal inhibitory concentration was strain-dependent. Spongistatin 1 was significantly more efficacious than amphotericin B in reducing kidney infectious burden in a murine model of disseminated candidiasis, and reduced the lung burden in a murine model of pulmonary cryptococcosis. When cryptococcal microtubules were visualized by fluorescence microscopy and iterative deconvolution, spongistatin 1 was shown to disrupt first cytoplasmic and then spindle microtubules in a time- and concentration-dependent manner. Microtubule disruption was accompanied by an abnormal distribution of nuclei in budding cells and an inhibition of cell division, resulting in cells arrested in a large-budded stage. Spongistatin 1 should be pursued as a potential antifungal agent and as a probe to study, major cellular processes.

Antineoplastic agents. 509: synthesis of fluorcombstatin phosphate and related 3-halostilbenes(1)

The present SAR study of combretastatin A-3 (3a) focused on replacement of the 3-hydroxyl group by a series of halogens. That approach with Z-stilbenes resulted in greatly enhanced (>10-100-fold) cancer cell growth inhibition against a panel of human cancer cell lines and the murine P388 lymphocytic leukemia cell line. Synthesis of the 3-fluoro-Z-stilbene designated fluorcombstatin (11a) and its potassium 3'-O-phosphate derivative (16c) by the route 7 --> 8a --> 11a --> 14 --> 16c illustrates the general synthetic pathway. The 3'-O-phosphoric acid ester (15) of 3-bromo-Z-stilbene 13a was also converted to representative cation salts to evaluate the potential for improved aqueous solubility, and the potassium salt (16 mg/mL in water) proved most useful. The fluoro (11a), chloro (12a), and bromo (13a) halocombstatins were nearly equivalent to combretastatin A-4 (1a) as inhibitors of tubulin polymerization and of the binding of colchicine to tubulin. The tubulin binding in cell-free systems was also retained in human umbilical vein endothelial cells. All three halocombstatins retained the powerful human cancer cell line inhibitory activity of combretastatin A-4 (1a) and proved superior to combretastatin A-3 (3a). In addition, the halocombstatins targeted Gram-positive bacteria and Cryptococcus neoformans.

Microplate Alamar blue assay for Staphylococcus epidermidis biofilm susceptibility testing

Biofilms are at the root of many infections largely because they are much more antibiotic resistant than their planktonic counterparts. Antibiotics that target the biofilm phenotype are desperately needed, but there is still no standard method to assess biofilm drug susceptibility. Staphylococcus epidermidis ATCC 35984 biofilms treated with eight different approved antibiotics and five different experimental compounds were exposed to the oxidation reduction indicator Alamar blue for 60 min, and reduction relative to untreated controls was determined visually and spectrophotometrically. The minimum biofilm inhibitory concentration was defined as < or = 50% reduction and a purplish well 60 min after the addition of Alamar blue. All of the approved antibiotics had biofilm MICs (MBICs) of >512 microg/ml (most >4,096 microg/ml), and four of the experimental compounds had MBICs of < or = 128 microg/ml. The experimental aaptamine derivative hystatin 3 was used to correlate Alamar blue reduction with 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) reduction and viable counts (CFU/ml) for S. epidermidis ATCC 35984, ATCC 12228, and two clinical isolates. For all four strains, Alamar blue results correlated well with XTT (r = 0.83 to 0.97) and with CFU/ml results (r = 0.85 to 0.94). Alamar blue's stability and lack of toxicity allowed CFU/ml to be determined from the same wells as Alamar blue absorbances. If the described method of microplate Alamar blue biofilm susceptibility testing, which is simple, reproducible, cost-effective, nontoxic, and amenable to high throughput, is applicable to other important biofilm forming species, it should greatly facilitate the discovery of biofilm specific agents.

Antineoplastic agents. 515. Synthesis of human cancer cell growth inhibitors derived from 3,4-methylenedioxy-5,4'-dimethoxy-3'-amino-Z-stilbene

Further structure-activity relationship (SAR) exploration of 3,4-methylenedioxy-5,4'-dimethoxy-3'-amino-Z-stilbene (1a) derivatives resulted in the efficient synthesis of tyrosine amide hydrochloride 9, two tyrosine amide phosphate prodrugs (3a and 6), and sodium aspartate amide 11. Two additional cancer cell growth inhibitors (14 and 16) were synthesized by employing peptide coupling between amine 1a and the Dap unit of dolastatin 10 (4a) to yield amide 14 followed by Dov-Val-Dil (15) to yield peptide 16. The latter represents a combination of stilbene 1a with the des-Doe tetrapeptide unit of the powerful tubulin assembly inhibitor dolastatin 10. Peptide 16 was examined for potential binding to tubulin in the vinca and/or colchicine regions and found to perform primarily as a relative of dolastatin 10. Amide 14 had anticryptococcal and antibacterial activities.

Antineoplastic Agents. 445. Synthesis and Evaluation of Structural Modifications of (Z)- and (E)-Combretastatin A-4

A series of cis- and trans-stilbenes related to combretastatin A-4 (1a), with a variety of substituents at the 3'-position of the aryl B-ring, were synthesized and evaluated for inhibitory activity employing six human cancer cell lines (NCI-H460 lung carcinoma, BXPC-3 pancreas, SK-N-SH neuroblastoma, SW1736 thyroid, DU-145 prostate, and FADU pharynx-squamous sarcoma) as well as the P-388 murine lymphocyte leukemia cell line. Several of the cis-stilbene derivatives were significantly inhibitory against all cell lines used, with potencies comparable to that of the parent 1a. All were potent inhibitors of tubulin polymerization. The corresponding trans-stilbenes had little or no activity as tubulin polymerization inhibitors and were relatively inactive against the seven cancer cell lines. In terms of inhibition of both cancer cell growth and tubulin polymerization, the dimethylamino and bromo cis-stilbenes were the most potent of the new derivatives, the latter having biological activity approaching that of 1a. As part of the present study, the X-ray crystal structure of the 3'-O-phosphate of combretastatin A-4 (1b) was successfully elucidated. Compound 1b has been termed the "combretastatin A-4 prodrug", and it is currently undergoing clinical trials for the treatment of human cancer patients.

Antineoplastic agents. 534. isolation and structure of sansevistatins 1 and 2 from the African Sansevieria ehrenbergii

Using bioactivity-directed isolation procedures, three new spirostanol saponins designated sansevierin A (1), sansevistatin 1 (2), and sansevistatin 2 (3) were isolated (10(-5) % yield) from the CH3OH-CH2Cl2 extract of Sansevieria ehrenbergii, accompanied by three known steroidal saponins (4-6). The structures were determined on the basis of chemical methods and spectroscopic analysis, especially 1D and 2D NMR experiments. Each of the saponins was evaluated against the P388 lymphocytic leukemia cell line and a panel of human cancer cell lines. Except for 1, all were found to cause inhibition of cancer cell growth. In addition, most of the saponins exhibited antimicrobial activity, particularly against the pathogenic fungi Candida albicans and Cryptococcus neoformans.

Antineoplastic agents 540. The Indian Gynandropsis gynandra (Capparidaceae)

The CH3OH-CH2Cl2 extract of an Indian collection (entire plant) of Gynandropsis gynandra (L.) Briq. was separated based on bioassay results employing cancer cell lines. Six cancer cell growth inhibitors were isolated and found to be known flavone apegenin (4) and flavonols 1-3, 5, and 6. The structure of flavonol 2 was confirmed by X-ray crystal structure determination. All of the five flavonols (1-3, 5, 6) inhibited the murine P388 lymphocytic leukemia cell line with ED50 values of 3.0, 9.2, 4.0, 0.37, and 3.9 microg/ml, respectively. All six of the flavonoids (1-6) also exhibited activity against a panel of six human cancer cell lines. Penduletin (3) inhibited growth of the Gram-negative pathogen Neisseria gonorrhoeae and apegenin (4) inhibited growth of the Gram-positive opportunist Enterococcus faecalis.

Antineoplastic agents. 529. Isolation and structure of nootkastatins 1 and 2 from the Alaskan yellow cedar Chamaecyparis nootkatensis

The yellow cedar tree, Chamaecyparis nootkatensis, collected in southeast Alaska was evaluated as a potential source of new anticancer agents. Two new diterpene anticancer constituents termed nootkastatins 1 (4) and 2 (5) were isolated along with three previously known diterpene cancer cell growth inhibitors where two were reported as synthetic modifications of totarol and not previously found in nature. All five diterpene structures were established by HRMS and 1D and 2D NMR spectroscopic analyses combined with three X-ray crystal structure determinations (2, 3, and 5). Against a panel of six human cancer cell lines, this series of diterpenes exhibited inhibition over the range GI(50) 0.75-2.0 microg/mL, and all inhibited the growth of Gram-positive bacteria and fungi.

Soil DNA libraries for anticancer drug discovery

Soil has the largest population of microbes of any habitat, but only about 0.3% of soil microbes are cultivable with current techniques. Cultured soil microbes have been an incredibly productive source of drugs, for example the cancer chemotherapeutics doxorubicin hydrochloride, bleomycin, daunorubicin and mitomycin. Unfortunately, the current yield of new drugs from soil microbes is low due to repeated cultivation of the same small fraction of cultivable microbes. Uncultured soil species represent a tremendous untapped resource of new antineoplastic agents. Methods have recently been developed to access the diversity of secondary metabolites from uncultured soil microbes. Briefly, total DNA is extracted from soil samples, purified, partially digested, and fragments inserted into vectors for expression in readily fermented microbes such as Escherichia coli. Clones expressing enzymatic and antibiotic activities that are encoded by novel sequences have been reported.

Differential gene expression in auristatin PHE-treated Cryptococcus neoformans

The antifungal pentapeptide auristatin PHE was recently shown to interfere with microtubule dynamics and nuclear and cellular division in the opportunistic pathogen Cryptococcus neoformans. To gain a broader understanding of the cellular response of C. neoformans to auristatin PHE, mRNA differential display (DD) and reverse transcriptase PCR (RT-PCR) were applied. Examination of approximately 60% of the cell transcriptome from cells treated with 1.5 times the MIC (7.89 micro M) of auristatin PHE for 90 min revealed 29 transcript expression differences between control and drug-treated populations. Differential expression of seven of the transcripts was confirmed by RT-PCR, as was drug-dependent modulation of an additional seven transcripts by RT-PCR only. Among genes found to be differentially expressed were those encoding proteins involved in transport, cell cycle regulation, signal transduction, cell stress, DNA repair, nucleotide metabolism, and capsule production. For example, RHO1 and an open reading frame (ORF) encoding a protein with 91% similarity to the Schizophyllum commune 14-3-3 protein, both involved in cell cycle regulation, were down-regulated, as was the gene encoding the multidrug efflux pump Afr1p. An ORF encoding a protein with 57% identity to the heat shock protein HSP104 in Pleurotus sajor-caju was up-regulated. Also, three transcripts of unknown function were responsive to auristatin PHE, which may eventually contribute to the elucidation of the function of their gene products. Further study of these differentially expressed genes and expression of their corresponding proteins are warranted to evaluate how they may be involved in the mechanism of action of auristatin PHE. This information may also contribute to an explanation of the selectivity of auristatin PHE for C. neoformans. This is the first report of drug action using DD in C. neoformans.

Antineoplastic Agents. 499. Synthesis of Hystatin 2 and Related 1H-Benzo[de][1,6]-naphthyridinium Salts from Aaptamine

The marine sponge constituent aaptamine (1) has been converted to the cancer cell growth inhibitor and antibiotic designated hystatin 2 (8a). Herein, we also report results of an initial SAR evaluation of new benzyl derivatives of aaptamine (1). Single benzylation was found to occur at nitrogen N-4 and led to the formation of the 4-benzylaaptamine derivatives 7a-c, whereas double benzylation gave the quaternary 1H-benzo[de][1,6]-naphthyridinium salts 8a-c. The anticancer and antimicrobial properties of these aaptamine derivatives are described. The quaternary ammonium salts 8a (hystatin 2) and 8b exhibited significant inhibitory activity against the murine P388 lymphocytic leukemia and a minipanel of human cancer cell lines. Salts 8a and 8b also had broad spectrum antimicrobial activities and were most potent against Mycobacterium tuberculosis, Neisseria gonorrhoeae, and Micrococcus luteus. Naphthyridinium chloride 8a was selected for further development, and results of an initial cell cycle analysis and a cDNA microarray study showed effects consistent with inhibition of the S-phase of cell growth.

Antineoplastic agents. 380. Isolation and X-ray crystal structure determination of isoaaptamine from the Republic of Singapore Hymeniacidon sp. and conversion to the phosphate prodrug hystatin 1

By use of bioassay (murine P388 lymphocytic leukemia cell line) guided isolation procedures, extracts of the Republic of Singapore marine sponge Hymeniacidon sp. were found to contain demethyloxyaaptamine (1) and aaptamine (3) as prominent cancer cell growth inhibitory constituents accompanied by the trace, albeit more active, component isoaaptamine (4). The isolation, X-ray structure elucidation, and antineoplastic and antimicrobial activities of isoaaptamine (4) have been summarized. Because of instability, isoaaptamine (4) was converted to a stable sodium phosphate prodrug designated hystatin 1 (7).

Antineoplastic Agents 491.1 Synthetic Conversion of Aaptamine to Isoaaptamine, 9-Demethylaaptamine, and 4-Methylaaptamine

Aaptamine (1) was used as starting material for synthetic transformation to isoaaptamine (2), 9-demethylaaptamine (5), and 4-methylaaptamine (6). A general method for the selective O-demethylation of such 1H-benzo[de][1,6]-naphthyridine (1) marine sponge constituents at position C-9 has been developed. Selective O-demethylation of aaptamine (1) and 1-methylaaptamine (11) with 48% hydrobromic acid led to 9-demethylaaptamine (5) and isoaaptamine (2), respectively. A selection of other aaptamine derivatives were synthesized, and their structures were unambiguously determined by X-ray methods. In addition, their cancer cell growth inhibitory properties were evaluated against the murine P388 lymphocytic cell line and a minipanel of human cancer cell lines. Evaluation as inhibitors of the PKC signal transduction pathway and against a selection of microorganisms was also undertaken. Aaptamine derivatives 3 and 5 had broad-spectrum antimicrobial activities.

Antineoplastic agents. 522. Hernandia peltata (Malaysia) and Hernandia nymphaeifolia (Republic of Maldives)

Bioassay (P388 lymphocytic leukemia cell line and human tumor cell lines)-guided separation of the extracts prepared from the tropical and coastal trees Hernandia peltata (Malaysia) and Hernandianymphaeifolia (Republic of Maldives) led to the isolation of a new lignan designated as hernanol (1) and 12 previously known lignans: (-)-deoxypodophyllotoxin (2), deoxypicropodophyllin (3), (+)-epiaschantin (4), (+)-epieudesmin (5), praderin (6), 5'-methoxyyatein (7), podorhizol (8), deoxypodorhizone (9), bursehernin (10), kusunokinol (11), clusin (12), and (-)-maculatin (13). The oxidative cyclization (with VOF(3)) of lignans 8, 9, and 10 resulted in a new and unusual benzopyran (14), isostegane (15), and a new dibenzocyclooctadiene lactone (16), respectively. The structure and relative stereochemistry of hernanol (1) and lignans 3, 7, 8, 9, 10, 11, and 12 were determined by 1D and 2DNMR and HRMS analyses. The structures and absolute stereochemistry of structures 2, 4, 5, 6, 13, 14, 15, and 16 were unequivocally determined by single-crystal X-ray diffraction analyses. Evaluation against the murine P388 lymphocytic leukemia cell line and human tumor cell lines showed podophyllotoxin derivatives 2 and 3 to be strong cancer cell line growth inhibitors and substances 4, 5, 8, and 15 to have marginal cancer cell line inhibitory activities. Seven of the lignans and one of the synthetic modifications (14) inhibited growth of the pathogenic bacterium Neisseria gonorrhoeae.

Antineoplastic Agents. 520. Isolation and Structure of Irciniastatins A and B from the Indo-Pacific Marine Sponge Ircinia ramosa

The Indo-Pacific marine sponge Ircinia ramosa has been found to contain two powerful (GI50 from 0.001 to <0.0001 microg/mL) murine and human cancer cell growth inhibitors. Both were isolated (10(-3)-10(-4)% yields) by cancer cell line bioassay-guided techniques and named irciniastatins A (1) and B (2). Structural elucidation by a combination of spectral analyses, primarily high resolution mass and 2D-NMR (principally APT, HMQC, HMBC, and ROESY) spectroscopy, revealed the unusual structures 1 and 2.

Antibacterial activity of the marine sponge constituent cribrostatin 6

The antibacterial activity of the nitrogen heterocyclic sponge constituent cribrostatin 6 was examined. Cribrostatin 6 was bacteriostatic for a variety of Gram-positive species and was bactericidal for the majority of clinical isolates of Streptococcus pneumoniae, including penicillin-resistant strains. Minimum bactericidal concentration/MIC ratios were < or =2 for 75 % of S. pneumoniae clinical isolates. Kill-curve analysis confirmed the bactericidal action of cribrostatin 6. Bactericidal activity was rather slow, beginning at 2, 4 or 8 h, depending on the strain. The frequency of occurrence of bacterial spontaneous mutations to resistance was < or =10(-7). The maximum tolerated dose of cribrostatin 6 in mice was 750-1000 micro g kg(-1) day(-1). Cribrostatin 6 is a promising lead antibiotic for Gram-positive bacteria, particularly S. pneumoniae, a leading cause of infection and mortality worldwide.

Isolation and structure of ruprechstyril from Ruprechtia tangarana

Bioassay (P388 lymphocytic leukemia cell line and human cancer cell lines)-guided separation of an extract prepared from the stem bark and twigs of the previously uninvestigated Ruprechtia tangarana led to the isolation of a new isocarbostyril designated ruprechstyril (1), secalonic acid A (2), 2'-O-methylevernic acid (3), 3,3',4-tri-O-methylflavellagic acid (4), lichexanthone (5), methyl asterrate (6), and 3beta,22E,24S-stigmasta-5,22-dien-3-ol (7). Only secalonic acid A exhibited cancer cell and microbial growth inhibition. The structure of ruprechstyril (1) was determined by HRMS and 1D and 2D NMR spectra and confirmed by single-crystal X-ray analysis. The structures and absolute stereochemistry of five of the other compounds were also established by X-ray crystal structure determination.

Antineoplastic agents. 485. Isolation and structure of cribrostatin 6, a dark blue cancer cell growth inhibitor from the marine sponge Cribrochalina sp

Cribrostatin 6, a dark blue cancer cell growth inhibiting (P388 ED(50) 0.3 microg/mL) constituent of the Republic of Maldives marine sponge Cribrochalina sp., has been assigned structure 3 on the basis of a combination of HRMS, high-field (500 MHz, HMBC, and GOESY experiments) (15)N, (1)H, and (13)C NMR, and X-ray crystal structure analyses. Cribrostatin 6 also was found to inhibit the growth of a number of pathogenic bacteria and fungi.