106 research outputs found
A hybrid time-frequency parametric modelling of medical ultrasound signal transmission
Medical ultrasound imaging is the most widespread real-time non-invasive
imaging system and its formulation comprises signal transmission, signal
reception, and image formation. Ultrasound signal transmission modelling has
been formalized over the years through different approaches by exploiting the
physics of the associated wave problem. This work proposes a novel
computational framework for modelling the ultrasound signal transmission step
in the time-frequency domain for a linear-array probe. More specifically, from
the impulse response theory defined in the time domain, we derived a parametric
model in the corresponding frequency domain, with appropriate approximations
for the narrowband case. To validate the model, we implemented a numerical
simulator and tested it with synthetic data. Numerical experiments demonstrate
that the proposed model is computationally feasible, efficient, and compatible
with realistic measurements and existing state-of-the-art simulators. The
formulated model can be employed for analyzing how the involved parameters
affect the generated beam pattern, and ultimately for optimizing measurement
settings in an automatic and systematic way
A stochastic approach to delays optimization for narrowband transmit beam pattern in medical ultrasound
Ultrasound imaging is extensively employed in clinical settings due to its
non-ionizing nature and real-time capabilities. The beamformer represents a
crucial component of an ultrasound machine, playing a significant role in
shaping the ultimate quality of the reconstructed image. Therefore, Transmit
Beam Pattern (TBP) optimization is an important task in medical ultrasound, but
state-of-the-art TBP optimization has well-known drawbacks like non-uniform
beam width over depth, presence of significant side lobes, and quick energy
drop out after the focal depth. To overcome these limitations, we developed a
novel optimization approach for TBP by focusing the analysis on its narrowband
approximation, particularly suited for Acoustic Radiation Force Impulse (ARFI)
elastography, and considering transmit delays as free variables instead of
linked to a specific focal depth. We formulate the problem as a non linear
Least Squares problem to minimize the difference between the TBP corresponding
to a set of delays and the desired one, modeled as a 2D rectangular shape
elongated in the direction of the beam axis. In order to quantitatively
evaluate the results, we define three quality metrics based on main lobe width,
side lobe level, and central line power. Results obtained by our synthetic
software simulation show that the main lobe width is considerably more intense
and uniform over the whole depth range with respect to classical focalized Beam
Patterns, and our optimized delay profile results in a combination of standard
delay profiles at different focal depths. The application of the proposed
method to ARFI elastography shows improvements in the concentration of the
ultrasound energy along a desired axis.Comment: 14 pages, 14 figure
Expression, intracellular targeting and purification of HIV Nef variants in tobacco cells
Background
Plants may represent excellent alternatives to classical heterologous protein expression systems, especially for the production of biopharmaceuticals and vaccine components. Modern vaccines are becoming increasingly complex, with the incorporation of multiple antigens. Approaches towards developing an HIV vaccine appear to confirm this, with a combination of candidate antigens. Among these, HIV-Nef is considered a promising target for vaccine development because immune responses directed against this viral protein could help to control the initial steps of viral infection and to reduce viral loads and spreading. Two isoforms of Nef protein can be found in cells: a full-length N-terminal myristoylated form (p27, 27 kDa) and a truncated form (p25, 25 kDa). Here we report the expression and purification of HIV Nef from transgenic tobacco.
Results
We designed constructs to direct the expression of p25 and p27 Nef to either the cytosol or the secretory pathway. We tested these constructs by transient expression in tobacco protoplasts. Cytosolic Nef polypeptides are correctly synthesised and are stable. The same is not true for Nef polypeptides targeted to the secretory pathway by virtue of a signal peptide. We therefore generated transgenic plants expressing cytosolic, full length or truncated Nef. Expression levels were variable, but in some lines they averaged 0.7% of total soluble proteins. Hexahistidine-tagged Nef was easily purified from transgenic tissue in a one-step procedure.
Conclusion
We have shown that transient expression can help to rapidly determine the best cellular compartment for accumulation of a recombinant protein. We have successfully expressed HIV Nef polypeptides in the cytosol of transgenic tobacco plants. The proteins can easily be purified from transgenic tissue
DNAM-1 chimeric receptor-engineered NK cells: a new frontier for CAR-NK cell-based immunotherapy
DNAM-1 is a major NK cell activating receptor and, together with NKG2D and NCRs, by binding specific ligands, strongly contributes to mediating the killing of tumor or virus-infected cells. DNAM-1 specifically recognizes PVR and Nectin-2 ligands that are expressed on some virus-infected cells and on a broad spectrum of tumor cells of both hematological and solid malignancies. So far, while NK cells engineered for different antigen chimeric receptors (CARs) or chimeric NKG2D receptor have been extensively tested in preclinical and clinical studies, the use of DNAM-1 chimeric receptor-engineered NK cells has been proposed only in our recent proof-of-concept study and deserves further development. The aim of this perspective study is to describe the rationale for using this novel tool as a new anti-cancer immunotherapy
Recent findings on the impact of ErbB receptors status on prognosis and therapy of head and neck squamous cell carcinoma
: Head and neck squamous cell carcinoma (HNSCC) is the sixth most common cancer type, has often an aggressive course and is poorly responsive to current therapeutic approaches, so that 5-year survival rates for patients diagnosed with advanced disease is lower than 50%. The Epidermal Growth Factor Receptor (EGFR) has emerged as an established oncogene in HNSCC. Indeed, although HNSCCs are a heterogeneous group of cancers which differ for histological, molecular and clinical features, EGFR is overexpressed or mutated in a percentage of cases up to about 90%. Moreover, aberrant expression of the other members of the ErbB receptor family, ErbB2, ErbB3 and ErbB4, has also been reported in variable proportions of HNSCCs. Therefore, an increased expression/activity of one or multiple ErbB receptors is found in the vast majority of patients with HNSCC. While aberrant ErbB signaling has long been known to play a critical role in tumor growth, angiogenesis, invasion, metastatization and resistance to therapy, more recent evidence has revealed its impact on other features of cancer cells' biology, such as the ability to evade antitumor immunity. In this paper we will review recent findings on how ErbB receptors expression and activity, including that associated with non-canonical signaling mechanisms, impacts on prognosis and therapy of HNSCC
DNAM-1-chimeric receptor-engineered NK cells, combined with Nutlin-3a, more effectively fight neuroblastoma cells in vitro: a proof-of-concept study
Adoptive transfer of engineered NK cells, one of clinical approaches to fight cancer, is gaining great interest in the last decade. However, the development of new strategies is needed to improve clinical efficacy and safety of NK cell-based immunotherapy. NK cell-mediated recognition and lysis of tumor cells are strictly dependent on the expression of ligands for NK cell-activating receptors NKG2D and DNAM-1 on tumor cells. Of note, the PVR/CD155 and Nectin-2/CD112 ligands for DNAM-1 are expressed primarily on solid tumor cells and poorly expressed in normal tissue cells. Here, we generated human NK cells expressing either the full length DNAM-1 receptor or three different DNAM-1-based chimeric receptor that provide the expression of DNAM-1 fused to a costimulatory molecule such as 2B4 and CD3ζ chain. Upon transfection into primary human NK cells isolated from healthy donors, we evaluated the surface expression of DNAM-1 and, as a functional readout, we assessed the extent of degranulation, cytotoxicity and the production of IFNγ and TNFα in response to human leukemic K562 cell line. In addition, we explored the effect of Nutlin-3a, a MDM2-targeting drug able of restoring p53 functions and known to have an immunomodulatory effect, on the degranulation of DNAM-1-engineered NK cells in response to human neuroblastoma (NB) LA-N-5 and SMS-KCNR cell lines. By comparing NK cells transfected with four different plasmid vectors and through blocking experiments, DNAM-1-CD3ζ-engineered NK cells showed the strongest response. Furthermore, both LA-N-5 and SMS-KCNR cells pretreated with Nutlin-3a were significantly more susceptible to DNAM-1-engineered NK cells than NK cells transfected with the empty vector. Our results provide a proof-of-concept suggesting that the combined use of DNAM-1-chimeric receptor-engineered NK cells and Nutlin-3a may represent a novel therapeutic approach for the treatment of solid tumors, such as NB, carrying dysfunctional p53
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