Somatic embryogenesis induction system for cloning an adult Cyphomandra betacea (Cav.) Sendt. (tamarillo)

Somatic embryogenesis is a valuable tool for plant breeding. In recent years, different aspects related to somatic embryogenesis (SE) induction in tamarillo have been studied at our laboratory. In this work, results concerning the establishment of a protocol for cloning an adult tamarillo tree through SE are presented. Attempts to induce SE in tamarillo from various explants directly taken from an adult tree were unsuccessful and only calli with no embryogenic potential were initiated. To overcome the lack of potential of adult tissues for SE, an indirect approach was attempted in which shoots from an adult tree were first established in vitro and then wounded leaves were used for SE induction. A low rate of embryogenic tissue formation was obtained (19.4%), but it was in the range of initiation rates from leaf explants of in vitro cloned plantlets of different tamarillo cultivars (red, orange and yellow) that originated from a single seedling (13.3–54.4%). High variation in SE initiation among juvenile controls could not be explained by different organogenetic potential, as no significant differences in shoot proliferation or rooting ability during micropropagation could be detected. Subcultures of embryogenic lines from the adult tree allowed us to obtain a large amount of embryogenic tissue that, after 8 weeks on a PGR-free medium, gave an average of 111 plants per gram of fresh mass of embryogenic tissue. A RAPD comparative analysis of somatic embryo-derived plantlets and the donor tree confirmed that the plantlets had no variation in the DNA regions amplified by 12 primers. These results open the way for large-scale cloning of elite tamarillo trees through SE.     

Determinants of choosing a career in family medicine

Background

Student choice is an important determinant of the distribution of specialties of practising physicians in many countries. Understanding characteristics at entry into medical school that are associated with the choice of residency in family medicine can assist medical schools in admitting an appropriate mix of students to serve the health care needs of their regions.

Methods

From 2002 to 2004, we collected data from students in 15 classes at 8 of 16 Canadian medical schools at entry. Surveys included questions on career choice, attitudes to practice and socio-demographic characteristics. We followed students prospectively with these data linked to their residency choice. We used multiple logistic regression analysis to identify entry characteristics that predicted a student’s ultimate career choice in family medicine.

Results

Of 1941 eligible students in the participating classes, 1542 (79.4%) contributed data to the final analyses. The following 11 entry variables predicted whether a student named family medicine as his or her top residency choice: being older, being engaged or in a long-term relationship, not having parents with postgraduate university education nor having family or close friends practicing medicine, having undertaken voluntary work in a developing nation, not volunteering with elderly people, desire for varied scope of practice, a societal orientation, a lower interest in research, desire for short postgraduate training, and lower preference for medical versus social problems.

Interpretation

Demographic and attitudinal characteristics at entry into medical school predicted whether students chose a career in family medicine.The number of physicians per capita in both Canada and the United States has declined, and this decline is expected to continue. Canada has already experienced a drop of 5.1% in the physician-to-population ratio from a peak in 2000, and in the United States a shortage of up to 200 000 physicians, or 20% of the needed workforce, is predicted to occur by 2025.^1,2 Combined with a growing elderly population and decreasing physician-hours,^3,4 this reduction in the physician-to-population ratio is expected to have implications for the health care systems of both countries. Therefore, health resource planners likely will be looking to expand the role of primary care, and of family medicine in particular.^5–8 To support such an expansion, a commensurate increase in the numbers of domestically trained family physicians will be required. But with as few as 25% (in 2003)⁹ of Canadian medical graduates choosing family medicine as their top career choice in the residency match, it is unlikely the health care system will be able to supply adequate numbers of primary care physicians.In most countries, the number and the distribution of specialties of physicians are determined by numerous factors, including government policies, training opportunities, immigration and emigration of providers, sex and age distribution of providers, and remuneration incentives and disincentives.^10–17 In many medical systems, the career interests of students also have a substantial steering effect on the distribution and number of available physicians.^18,19The purpose of this study was to follow a large cohort of Canadian medical students from school entry through exit to examine how their career aspirations changed over time and to identify, using multiple logistic regression analysis, the variables at entry into medical school that predict a career choice of family medicine at graduation.     

Discovery of potent nucleotide-mimicking competitive inhibitors of hepatitis C virus NS3 helicase

Among the enzymes involved in the life cycle of HCV, the non-structural protein NS3, with its double function of protease and NTPase/helicase, is essential for the virus replication. Exploiting our previous knowledge in the development of nucleotide-mimicking NS3 helicase (NS3h) inhibitors endowed with key structural and electronic features necessary for an optimal ligand-enzyme interaction, we developed the tetrahydroacridinyl derivative 3a as the most potent NS3h competitive inhibitor reported to date (HCV NS3h K(i)=20 nM).     

Discovery of a novel series of selective HCN1 blockers

The discovery of a series of novel, potent, and selective blockers of the cyclic nucleotide-modulated channel HCN1 is disclosed. Here we report an SAR study around a series of selective blockers of the HCN1 channel. Utilization of a high-throughput VIPR assay led to the identification of a novel series of 2,2-disubstituted indane derivatives, which had moderate selectivity and potency at HCN1. Optimization of this hit led to the identification of the potent, 1,1-disubstituted cyclohexane HCN1 blocker, 2-ethoxy-N-((1-(4-isopropylpiperazin-1-yl)cyclohexyl)methyl)benzamide. The work leading to the discovery of this compound is described herein.     

A Pd-mediated new strategy to functionalized 2-aminochromenes: their in vitro evaluation as potential anti tuberculosis agents

A multi component based synthesis involving palladium catalyzed C-C bond forming reaction has been developed as a new strategy to access systematically modified functionalized 2-aminochromenes. This MCR involves the use of bromobenzaldehyde as a key component and is highlighted by generating a new compound library. Many of these compounds showed Mycobacterium tuberculosis H37Rv chorismate mutase inhibiting properties in vitro representing the lead example of chorismate mutase inhibition by heteroarene based compounds.     

The origin and dynamic evolution of chemical information transfer

Although chemical communication is the most widespread form of communication, its evolution and diversity are not well understood. By integrating studies of a wide range of terrestrial plants and animals, we show that many chemicals are emitted, which can unintentionally provide information (cues) and, therefore, act as direct precursors for the evolution of intentional communication (signals). Depending on the content, design and the original function of the cue, there are predictable ways that selection can enhance the communicative function of chemicals. We review recent progress on how efficacy-based selection by receivers leads to distinct evolutionary trajectories of chemical communication. Because the original function of a cue may channel but also constrain the evolution of functional communication, we show that a broad perspective on multiple selective pressures acting upon chemicals provides important insights into the origin and dynamic evolution of chemical information transfer. Finally, we argue that integrating chemical ecology into communication theory may significantly enhance our understanding of the evolution, the design and the content of signals in general.     

CyLoP-1: a novel cysteine-rich cell-penetrating peptide for cytosolic delivery of cargoes

Cell-penetrating peptides (CPPs) may have impli-cations in biomedical sciences by improving the delivery of a wide variety of drugs through the membrane barrier. CPPs are generally taken up by endocytotic pathways, and vesicular encapsulation is a limiting factor in the area of intracellular targeting. A novel, cationic cysteine-rich CPP, CyLoP-1, has been developed exhibiting distinguished diffused cytosolic distribution along with endosomal uptake at low micromolar concentrations. Comparative uptake analysis with known CPPs showed CyLoP-1 as a promising delivery vector to access the cytosol in a variety of cell types. In addition to the positively charged residues, the presence of cysteines and tryptophans proved to be essential to maintain its functionality. Also, the oxidation status of the cysteines played an important role for the uptake efficiency of CyLoP-1, with the disulfide-containing form being more effective. The distinct feature of CyLoP-1 to enter the cytosol was further explored by the covalent attachment of cargoes of different nature and sizes. In particular, induction of caspase-3 activity (indicating apoptosis) by a CyLoP-1-SmacN7 conjugate proved successful delivery of the pro-apoptotic cargo to its site of action in the cytosol. Efficient intracellular delivery into the entire cytosol already at low micromolar concentrations makes CyLoP-1 a promising candidate for cytosolic delivery of cargoes of small sizes. Thus, this peptide might prove to be useful for efficient transmembrane delivery of agents directed to cytosolic targets.