Improving Image Quality by Accounting for Changes in Water Temperature during a Photoacoustic Tomography Scan

The emerging field of photoacoustic tomography is rapidly evolving with many new system designs and reconstruction algorithms being published. Many systems use water as a coupling medium between the scanned object and the ultrasound transducers. Prior to a scan, the water is heated to body temperature to enable small animal imaging. During the scan, the water heating system of some systems is switched off to minimize the risk of bubble formation, which leads to a gradual decrease in water temperature and hence the speed of sound. In this work, we use a commercially available scanner that follows this procedure, and show that a failure to model intra-scan temperature decreases as small as 1.5°C leads to image artifacts that may be difficult to distinguish from true structures, particularly in complex scenes. We then improve image quality by continuously monitoring the water temperature during the scan and applying variable speed of sound corrections in the image reconstruction algorithm. While upgrading to an air bubble-free heating pump and keeping it running during the scan could also solve the changing temperature problem, we show that a software correction for the temperature changes provides a cost-effective alternative to a hardware upgrade. The efficacy of the software corrections was shown to be consistent across objects of widely varying appearances, namely physical phantoms, ex vivo tissue, and in vivo mouse imaging. To the best of our knowledge, this is the first study to demonstrate the efficacy of modeling temporal variations in the speed of sound during photoacoustic scans, as opposed to spatial variations as focused on by previous studies. Since air bubbles pose a common problem in ultrasonic and photoacoustic imaging systems, our results will be useful to future small animal imaging studies that use scanners with similarly limited heating units.     

Poly-β-hydroxybutyrate accumulation in bacterial consortia from different environments

The aim of the present study was to examine soil samples from various vegetation zones in terms of physicochemical properties, microbial communities, and isolation and identification (by polymerase chain reaction and transmission electron microscopy) of bacteria producing poly-β-hydroxybutyrates (PHBs). Soil samples were analysed originating from zones with heterogeneous environmental conditions from the Romanian Carpathian Mountains (mountain zone with alpine meadow, karstic zone with limestone meadow, hill zone with xerophilous meadow, and flood plain zone with hygrophilic meadow). Different bacterial groups involved in the nitrogen cycle (aerobic mesophilic heterotrophs, ammonifiers, denitrifiers, nitrifiers, and free nitrogen-fixing bacteria from Azotobacter genus) were analysed. Soil biological quality was assessed by the bacterial indicator of soil quality, which varied between 4.3 and 4.7. A colony polymerase chain reaction technique was used for screening PHB producers. With different primers, specific bands were obtained in all the soil samples. Some wild types of Azotobacter species were isolated from the 4 studied sites. Biodegradable polymers of PHB were assessed by negative staining in transmission electron microscopy. The maximum PHB granules density was obtained in the strains isolated from the xerophilous meadow (10-18 granules/cell), which was the most stressful environment from all the studied sites, as the physicochemical and microbiological tests proved.     

Analysis of CYP2C9*2, CYP2C9*3 and VKORC1 ‐1639 G>A polymorphisms in a population from South‐Eastern Europe

The CYP2C9 enzyme metabolizes a wide range of relevant drugs, among which are oral anticoagulants. VKORC1 is the pharmacodynamic target of the oral anticoagulants. The genetic polymorphisms CYP2C9*2, CYP2C9*3 and VKORC1 ‐1639 G>A are the major determinants of the inter‐individual variability in the dosage requirements of oral anticoagulants. This study provides a first evaluation of these 3 polymorphisms in a Romanian population. A total of 332 Romanian individuals were genotyped for the CYP2C9*2, CYP2C9*3 and VKORC1 ‐1639 G>A polymorphisms using the PCR‐RFLP technique. Sixty‐two individuals (18.7%) were heterozygous for CYP2C9*2, whereas 47 individuals (14.1%) were heterozygous for CYP2C9*3. Fourteen individuals (4.2%) had a CYP2C9*2 homozygous, CYP2C9*3 homozygous or CYP2C9*2/CYP2C9*3 compound heterozygous genotype. These individuals are predicted to have the lowest CYP2C9 enzymatic activity. The allele frequencies of the CYP2C9*2 and CYP2C9*3 polymorphisms were 11.3% and 9.3% respectively. For the VKORC1 ‐1639 G>A polymorphism, there were 170 heterozygotes (51.2%) and 55 (16.6%) homozygotes for the A allele. The frequency of the A allele was 42.2%. Overall, the distribution of the CYP2C9*2, CYP2C9*3 and VKORC1 ‐1639 G>A polymorphisms observed in our cohort is in accordance with other Caucasian populations. A large number of Romanians are expected to harbour at least one CYP2C9 variant allele and/or one VKORC1 ‐1639 G>A allele. This frequency has major implications in the pharmacogenomics of oral anticoagulants in Romanians.     

Schizophrenia--a parameters' game?

Schizophrenia is a severe, currently incurable, relatively common mental condition. Its symptoms are complex and widespread. It structurally and functionally affects cortical and subcortical regions involved in cognitive, emotional and motivational aspects of behavior. Its diagnosis is based on statistical behavior rather than on its actual cause and its treatment is elusive.We elaborate a theoretical paradigm that accounts for some of the most important features of this illness. Our nonlinear mathematical model, built upon recent hypotheses of neural vulnerability and limbic dysregulation, addresses the amygdala—hippocampus—prefrontal interactions and their evolution under perturbation. The dependence of the dynamics on the system's parameters offers an analytical context for the “normality/disease” dichotomy. The concept of bifurcation could be the key to understanding the threshold between these two states.The nonlinearity parameter (Lyapunov number) is responsible in our setup for tuning the limbic vulnerability characteristic to schizophrenia. Studying its effect on the dynamics helps us understand how stressful events and medication can switch the system from a regime of safety to one of instability, and conversely. The approach has potential for pre-symptomatic risk assessments and for long-term predictions.     

New dimensions in tumor immunology: what does 3D culture reveal?

Experimental models indicate that tumor cells in suspension, unlike solid tumor fragments, might be unable to produce life-threatening cancer outgrowth when transferred to animal models, irrespective of the number of cells transferred, although they induce specific immune responses. Human tumor cells cultured in three dimensions display increased pro-angiogenic capacities and resistance to interferons, chemotherapeutic agents or irradiation, as compared with cells cultured in two-dimensional (2D) monolayers. Tumor cells cultured in three dimensions were also shown to be characterized by defective immune recognition by cytotoxic T lymphocytes (CTLs) specific for tumor-associated antigens (TAAs) and by a capacity to inhibit CTL proliferation and dendritic cell (DC) functions. Downregulation of human leukocyte antigen (HLA) or TAA expression and high production of lactic acid might play a role in the elicitation of these effects. Here, we propose that growth in 3D architectures might provide new insights into tumor immunology and could represent an integral missing component in pathophysiological tumor immune escape mechanisms.     

Activated epidermal growth factor receptor as a novel target in pancreatic cancer therapy

Pancreatic cancer is one of the most fatal among all solid malignancies. Targeted therapeutic approaches have the potential to transform cancer therapy as exemplified by the success of several tyrosine kinase inhibitors. Prompted by this, comprehensive profiling of tyrosine kinases and their substrates was carried out using a panel of low passage pancreatic cancer cell lines. One of the pancreatic cancer cell lines, P196, which showed dramatic upregulation of tyrosine kinase activity as compared to non-neoplastic cells, was systematically studied using a quantitative proteomic approach called stable isotope labeling with amino acids in cell culture (SILAC). A careful analysis of activated tyrosine kinase pathways revealed aberrant activation of epidermal growth factor receptor pathway in this cell line. Mouse xenograft based studies using EGFR inhibitor erlotinib confirmed EGFR pathway to be responsible for proliferation in these tumors. By a systematic study across low passage pancreatic cancer cell lines and mice carrying pancreatic cancer xenografts, we have demonstrated activated epidermal growth factor receptor as an attractive candidate for targeted therapy in a subset of pancreatic cancers. Further, we propose immunohistochemical labeling of activated EGFR (pEGFR (1068)) as an efficient screening tool to select patients who are more likely to respond to EGFR inhibitors.     

Simultaneous detection and quantification of the unculturable microbe Candidatus Glomeribacter gigasporarum inside its fungal host Gigaspora margarita

A combined approach based on quantitative and nested polymerase chain reaction (qPCR and nPCR, respectively) has been set up to detect and quantify the unculturable endobacterium Candidatus Glomeribacter gigasporarum inside the spores of its fungal host Gigaspora margarita. Four genes were targeted, two of bacterial origin (23S rRNA gene and rpoB) and two from the fungus (18S rRNA gene and EF1-alpha). The sensitivity of the qPCR protocol has proved to be comparable to that of nPCR, both for the fungal and the bacterial detection. It has been demonstrated that the last detected dilution in qPCR corresponded, in each case, to 10 copies of the target sequences, suggesting that the method is equally sensitive for the detection of both fungal and bacterial targets. As the two targeted bacterial genes are predicted to be in single copy, it can be concluded that the detection limit is of 10 bacterial genomes for each mixture. The protocol was then successfully applied to amplify fungal and bacterial DNA from auxiliary cells and extraradical and intraradical mycelium. For the first time qPCR has been applied to a complex biological system to detect and quantify fungal and bacterial components using single-copy genes, and to monitor the bacterial presence throughout the fungal life cycle.     

Kinetics and persistence of cellular and humoral immune responses to SARS‐CoV‐2 vaccine in healthcare workers with or without prior COVID‐19

SARS‐CoV‐2 vaccines are highly efficient against severe forms of the disease, hospitalization and death. Nevertheless, insufficient protection against several circulating viral variants might suggest waning immunity and the need for an additional vaccine dose. We conducted a longitudinal study on the kinetics and persistence of immune responses in healthcare workers vaccinated with two doses of BNT162b2 mRNA vaccine with or without prior SARS‐CoV‐2 infection. No new infections were diagnosed during follow‐up. At 6 months, post‐vaccination or post‐infection, despite a downward trend in the level of anti‐S IgG antibodies, the neutralizing activity does not decrease significantly, remaining higher than 75% (85.14% for subjects with natural infection, 88.82% for vaccinated after prior infection and 78.37% for vaccinated only). In a live‐virus neutralization assay, the highest neutralization titres were present at baseline and at 6 months follow‐up in persons vaccinated after prior infection. Anti‐S IgA levels showed a significant descending trend in vaccinated subjects (p < 0.05) after 14 weeks. Cellular immune responses are present even in vaccinated participants with declining antibody levels (index ratio 1.1–3) or low neutralizing activity (30%–40%) at 6 months, although with lower T‐cell stimulation index (p = 0.046) and IFN‐γ secretion (p = 0.0007) compared to those with preserved humoral responses.