Target fishing reveals PfPYK-1 and PfRab6 as potential targets of an antiplasmodial 4-anilino-2-trichloromethylquinazoline hit compound

We present investigations about the mechanism of action of a previously reported 4-anilino-2-trichloromethylquinazoline antiplasmodial hit-compound (Hit A), which did not share a common mechanism of action with established commercial antimalarials and presented a stage-specific effect on the erythrocytic cycle of P. falciparum at 8 < t < 16 h. The target of Hit A was searched by immobilising the molecule on a solid support via a linker and performing affinity chromatography on a plasmodial lysate. Several anchoring positions of the linker (6,7 and 3') and PEG-type linkers were assessed, to obtain a linked-hit molecule displaying in vitro antiplasmodial activity similar to that of unmodified Hit A. This allowed us to identify the PfPYK-1 kinase and the PfRab6 GTP-ase as potential targets of Hit A.

Magnetic anisotropy, magnetization reversal and switching in Ni4Nb2O9single crystals

Ni4Nb2O9is an insulating compensated ferrimagnet withTN= 77 K andTcomp= 33 K. We report here the study of the magnetic anisotropy using millimeter-size crystals grown in an image furnace. The magnetization measurements, vs temperature, performed withHaligned along the three main crystallographic axes, show similar Curie-Weiss temperatures (Θp≈ 190 K) and rather similar effective paramagnetic moments (from 3.5μBto 3.6μB). This suggests that the strongest magnetic interaction is the antiferromagnetic one, coupling the ferromagnetic distorted honeycomb layers and zigzag ribbons via face sharing NiO6octahedra. This strong antiferromagnetic coupling is supported by DFT calculations that do not evidence any inter site ferromagnetic interaction, leading to total compensation between magnetic moments of both Ni2+sites. Measurements vs magnetic field belowTNreveal an anisotropic behaviour, with square magnetization loops forHin theabplane, whereas linearM(H) curves without hysteresis are observed forH‖c. This anisotropy betweenabplane andcaxis occurs also in the magnetization reversal (MR), which is observed in theabplane only. Starting fromM(H) virgin curves collected just belowTcomp= 33 K withH‖aorH‖b, the memory-like effect was tested through magnetization switching induced byHorTalternating changes. BelowTcomp, smallerHis needed to switchMsymmetrically forHalongbthan alonga, and, forTswitching (2 K interval, constantH), a largerMchange is obtained alongathan alongb. The comparison with ferrimagnetic oxides which exhibit MR, like spinels or rare earth orthoferrites, shows that Ni4Nb2O9is unique since only one magnetic cation over two sites in octahedral coordination is at play, thus providing a unique platform to studyMswitching but also a challenge for theoretical interpretation.

Alternation of inverse problem approach and deep learning for lens-free microscopy image reconstruction

A lens-free microscope is a simple imaging device performing in-line holographic measurements. In the absence of focusing optics, a reconstruction algorithm is used to retrieve the sample image by solving the inverse problem. This is usually performed by optimization algorithms relying on gradient computation. However the presence of local minima leads to unsatisfactory convergence when phase wrapping errors occur. This is particularly the case in large optical thickness samples, for example cells in suspension and cells undergoing mitosis. To date, the occurrence of phase wrapping errors in the holographic reconstruction limits the application of lens-free microscopy in live cell imaging. To overcome this issue, we propose a novel approach in which the reconstruction alternates between two approaches, an inverse problem optimization and deep learning. The computation starts with a first reconstruction guess of the cell sample image. The result is then fed into a neural network, which is trained to correct phase wrapping errors. The neural network prediction is next used as the initialization of a second and last reconstruction step, which corrects to a certain extent the neural network prediction errors. We demonstrate the applicability of this approach in solving the phase wrapping problem occurring with cells in suspension at large densities. This is a challenging sample that typically cannot be reconstructed without phase wrapping errors, when using inverse problem optimization alone.

Quantitative phase imaging of adherent mammalian cells: a comparative study

The Quantitative phase imaging methods have several advantages when it comes to monitoring cultures of adherent mammalian cells. Because of low photo-toxicity and no need for staining, we can follow cells in a minimally invasive way over a long period of time. The ability to measure the optical path difference in a quantitative manner allows the measurement of the cell dry mass, an important metric for studying the growth kinetics of mammalian cells. Here we present and compare cell measurements obtained with three different techniques: digital holographic microscopy, lens-free microscopy and quadriwave lateral sheering interferometry. We report a linear relationship between optical volume density values measured with these different techniques and estimate the precisions of this measurement for the different individual instruments.

Fluorescence diffuse optical tomographic (fDOT) system for small animal studies

This paper presents a new fluorescence diffuse optical tomographic (fDOT) system and its associated reconstruction method. It is able to reconstruct the fluorescence yield even in heterogeneous and highly attenuating regions. Furthermore our reconstruction method makes mouse inspection without immersion in optical index matching liquid (Intralipid and ink) possible. Some phantom experiments have been carried out to characterize this new fDOT system and to validate its use for heterogeneous media. A mice study consisting in the follow up of the lungs at different stages of tumor development is then related. These results validate the use of our system for biological studies of small animals.

Noncontact fluorescence diffuse optical tomography of heterogeneous media

Fluorescence-enhanced diffuse optical tomography is expected to be useful to the collection of functional information from small animal models. This technique is currently limited by the extent of tissue heterogeneity and management of the shape of the animals. We propose an approach based on the reconstruction of object heterogeneity, which provides an original solution to the two problems. Three evaluation campaigns are described: the first two were performed on phantoms designed to test the reconstructions in highly heterogeneous media and noncontact geometries; the third was conducted on mice with lung tumors to test fluorescence yield reconstruction feasibility in vivo.

[Specialty certification for physicians with pre or postgraduate degree who studied abroad. Experience of the National Autonomous Commission for the Certification of Medical Specialties (CONACEM)]

BACKGROUND

The number of foreign or Chilean physicians with pre or postgraduate studies abroad, seems to be increasing.

AIM

To report the experience of CONACEM in the certification of specialties for Chilean or foreign physicians that studied abroad.

MATERIALS AND METHODS

The certification process for 90 physicians (38 Chilean and 52 foreign) with studies abroad is reported. Criteria for certification of specialties were the same used for physicians with studies in Chile and results were compared with those obtained by the latter.

RESULTS

Physicians with studies abroad required additional evaluations with a greater frequency than local physicians, due to the fact that foreign training programs are not well known by CONACEM members. Eighty five percent of foreign physicians required those further evaluations, compared with 66.6% of all physicians certified by the commission. Fifty five percent of Chilean physicians with studies abroad did not accept this additional assessment. Applications for specialties of physicians with studies abroad, were rejected with a greater frequency than those of Chilean physicians (31% and 13%, respectively).

CONCLUSIONS

Physicians with studies abroad applying for certification of medical specialties required more evaluations and were rejected with a greater frequency than Chilean physicians.

[Experience of the National Autonomous Board for Certification of Medical Specialties]

After 6 years of operation of a National (autonomous) Board for Certification of Medical Specialists, the number, distribution and training of medical specialists is analyzed. Problems regarding significant differences in the quality of training and imbalance among different specialties are identified. The medical profession has expressed its confidence and feels supported by the activities of the Board. However, health care deliverers and users in general are expected to increase their support and consideration for the information provided by the Board, in order to fulfill the purpose for which it was established.