Regulation of lactose, glucose and sucrose metabolisms in S. thermophilus

Streptococcus thermophilus is a bacterium widely used in the production of yogurts and cheeses, where it efficiently ferments lactose, the saccharide naturally present in milk. It is also employed as a starter in dairy- or plant-based fermented foods that contain saccharides other than lactose (e.g., sucrose, glucose). However, little is known about how saccharide use is regulated, in particular when saccharides are mixed. Here, we determine the effect of the 5 sugars that S. thermophilus is able to use, at different concentration and when they are mixed on the promoter activities of the C-metabolism genes. Using a transcriptional fusion approach, we discovered that lactose and glucose modulated the activity of the lacS and scrA promoters in a concentration-dependent manner. When mixed with lactose, glucose also repressed the two promoter activities; when mixed with sucrose, lactose still repressed scrA promoter activity. We determined that catabolite control protein A (CcpA) played a key role in these dynamics. We also showed that promoter activity was linked with glycolytic flux, which varied depending on saccharide type and concentration. Overall, this study identified key mechanisms in carbohydrate metabolism - autoregulation and partial hierarchical control - and demonstrated that they are partly mediated by CcpA.

Towards virtual histology with X-ray grating interferometry

Breast cancer is the most common type of cancer worldwide. Diagnosing breast cancer relies on clinical examination, imaging and biopsy. A core-needle biopsy enables a morphological and biochemical characterization of the cancer and is considered the gold standard for breast cancer diagnosis. A histopathological examination uses high-resolution microscopes with outstanding contrast in the 2D plane, but the spatial resolution in the third, Z-direction, is reduced. In the present paper, we propose two high-resolution table-top systems for phase-contrast X-ray tomography of soft-tissue samples. The first system implements a classical Talbot-Lau interferometer and allows to perform ex-vivo imaging of human breast samples with a voxel size of 5.57 μm. The second system with a comparable voxel size relies on a Sigray MAAST X-ray source with structured anode. For the first time, we demonstrate the applicability of the latter to perform X-ray imaging of human breast specimens with ductal carcinoma in-situ. We assessed image quality of both setups and compared it to histology. We showed that both setups made it possible to target internal features of breast specimens with better resolution and contrast than previously achieved, demonstrating that grating-based phase-contrast X-ray CT could be a complementary tool for clinical histopathology.

Secondary ossification center induces and protects growth plate structure

Growth plate and articular cartilage constitute a single anatomical entity early in development but later separate into two distinct structures by the secondary ossification center (SOC). The reason for such separation remains unknown. We found that evolutionarily SOC appears in animals conquering the land - amniotes. Analysis of the ossification pattern in mammals with specialized extremities (whales, bats, jerboa) revealed that SOC development correlates with the extent of mechanical loads. Mathematical modeling revealed that SOC reduces mechanical stress within the growth plate. Functional experiments revealed the high vulnerability of hypertrophic chondrocytes to mechanical stress and showed that SOC protects these cells from apoptosis caused by extensive loading. Atomic force microscopy showed that hypertrophic chondrocytes are the least mechanically stiff cells within the growth plate. Altogether, these findings suggest that SOC has evolved to protect the hypertrophic chondrocytes from the high mechanical stress encountered in the terrestrial environment.

Assembly of functionalized silk together with cells to obtain proliferative 3D cultures integrated in a network of ECM-like microfibers

Tissues are built of cells integrated in an extracellular matrix (ECM) which provides a three-dimensional (3D) microfiber network with specific sites for cell anchorage. By genetic engineering, motifs from the ECM can be functionally fused to recombinant silk proteins. Such a silk protein, FN-silk, which harbours a motif from fibronectin, has the ability to self-assemble into networks of microfibers under physiological-like conditions. Herein we describe a method by which mammalian cells are added to the silk solution before assembly, and thereby get uniformly integrated between the formed microfibers. In the resulting 3D scaffold, the cells are highly proliferative and spread out more efficiently than when encapsulated in a hydrogel. Elongated cells containing filamentous actin and defined focal adhesion points confirm proper cell attachment to the FN-silk. The cells remain viable in culture for at least 90 days. The method is also scalable to macro-sized 3D cultures. Silk microfibers formed in a bundle with integrated cells are both strong and extendable, with mechanical properties similar to that of artery walls. The described method enables differentiation of stem cells in 3D as well as facile co-culture of several different cell types. We show that inclusion of endothelial cells leads to the formation of vessel-like structures throughout the tissue constructs. Hence, silk-assembly in presence of cells constitutes a viable option for 3D culture of cells integrated in a ECM-like network, with potential as base for engineering of functional tissue.

Abstract 102: Semi-Automatic Measurement of External and Luminal Diameter Predicts the Four-Year Prognosis of Small Abdominal Aortic Aneurysms

Objective: Predicting which abdominal aortic aneurysms (AAA) will require surgery and which may remain stable remains a challenge. We set out to evaluate whether semi-automatic diameter measurements and finite element analysis (FEA) might predict the four-year prognosis of AAAs more precisely than standard diameter measurements.

Methods: From a retrospective dataset of 97 patients with aneurysm baseline diameter of 40-50 mm, 39 AAAs remained below 55 mm in diameter for four years whilst 58 expanded beyond 54 mm within four years, or were treated surgically. Standard diameters, measured by radiologists or vascular surgeons, were recorded at baseline and at follow-up. Maximal external and luminal diameters as well as total and luminal volume were semi-automatically re-measured from 3D models based on CT images. FEA, estimating the peak wall rupture index (PWRI), was subsequently performed. Further, in 94 patients from the dataset, standard diameter growth rates between baseline and follow-up were calculated.

Results: Aneurysms that would require surgery within four years were identified with 100% specificity by semi-automatic diameter, n=13 (22%), luminal diameter, n=14 (24%), PWRI, n=7 (12%), and luminal volume, n=5 (8.6%). Neither standard diameter nor total volume could reach 100% specificity. AAA diameter growth rate correlated with baseline semi-automatic diameter (r=0.39, p=9.2e-5), luminal diameter (r=0.29, p=0.005) and luminal volume (r=0.23, p=0.027) but not with PWRI (r=0.17, p=0.094), total volume (r=0.16, p=0.13), nor standard diameter (r=0.14, p=0.17).

Conclusion: In AAAs with small diameters, precise, semiautomatic measurement of the maximal external and luminal diameter is able to specifically identify aneurysms requiring surgery within four years.

Abstract 321: The Aortic Luminal Area is a Potential Marker of Increased Rupture Risk in AbdominalAorticAneurysms

Introduction: Diameter is currently the only factor used to estimate rupture risk of abdominal aortic aneurysms (AAAs). Many large AAAs, however, do not rupture, and a significant portion of small AAAs do. Our aim was to investigate if simple two-dimensional geometric measurements can improve rupture risk prediction in AAAs, and relate these measurements to biomechanical determinants of AAAs.

Methods: Thirty patients with ruptured AAAs (mean age was 77 ± 5 years and 23 were male) and 60 patients (mean age 60 ± 8 years, and 46 were male) with asymptomatic AAAs were included. At the location of the maximal diameter, the diameter, the luminal area and the vessel area were measured. Finite element analysis was used to compute 3D-geometric and biomechanical parameters of the asymptomatic AAAs, using A4 Clinics Software (VASCOPS, Austria). An automatic matching function was used to construct diameter-matched groups.

Results: Analysis of all stable AAAs (n=60) and ruptured AAAs (n=30) showed that ruptured AAAs had a significantly larger diameter, 77 ± 15 mm vs. 62 ± 13 mm (p<0.01) and significantly larger luminal area 2281 ± 1964 mm 2 vs. 1059 ± 674 mm 2 (p<0.01). In order to control for diameter as a confounder, two diameter-matched groups, one with ruptured AAAs (n=28) and one with stable AAAs (n=15) were formed (74 ± 12 mm vs 73 ± 11, p = .67). Diameter-matched ruptured AAAs had a larger luminal area (1954 ± 1254 mm 2 vs. 1120 ± 623 mm 2 , p = .02) and a lower relative ILT area (55 ± 24 % vs 68 ± 24%, p= .03). In multivariate regression of 60 asymptomatic AAAs, including the maximal diameter, the luminal area explained the largest amount of variance in the biomechanical rupture risk parameters, followed by the ILT-area.

Conclusions: We demonstrate that the luminal area is increased in ruptured AAAs compared to stable AAAs. Further, we show that this finding may in part be explained by a correlation between luminal area and biomechanical rupture risk parameters.

Abstract 107: Finite Element Models With Patient-Specific Wall Strength Estimations Improve Growth Predictions of Abdominal Aortic Aneurysms

OBJECTIVES: Abdominal aortic aneurysms (AAA) grow discontinuously and there is no reliable method to predict growth rate specifically. If AAA growth rate could be predicted, surveillance intervals and elective surgery could be planned in a safe and cost-efficient manner. In this study, we used finite element modeling (FEM) with estimations of patient specific factors including wall strength and wall thickness to find a biomechanical parameter that predicted AAA growth.

METHODS: 41 patients (9 women, 32 men) who had undergone two computed tomography angiographies (CT-A) within 9-18 months were included. Two FEM were made per CT-A; one (standard) with and one (matched) without modeling influence of patient specific age, sex, mean arterial pressure and family history. Annual growth of diameter and volume were measured. The baseline AAA volume, diameter, intraluminal thrombus (ILT) volume, mean wall stress (MWS), mean ILT stress (MIS), peak wall stress (PWS) and peak wall rupture risk (PWRR = maximal wall stress/wall strength ratio) were estimated. Linear and non-linear correlations between growth and biomechanical parameters were tested with Pearson product-moment and Spearman’s rank correlation coefficients, respectively.

RESULTS: Standard baseline PWRR correlated with diameter growth (r=0.32 P=0.040). Baseline AAA volume (r=0.57 P=0.0001), diameter (r=0.53 P = 0.0003), ILT volume (r=0.50, P=0.0009), standard (r=0.44 P=0.0087) and matched (r=0.32 P=0,043) PWRR and matched MIS (r=0.39 P=0.013) correlated with volume growth. PWS and MWS did not correlate with AAA growth.

CONCLUSIONS: PWRR, based on patient specific wall stress and strength estimations, can predict both diameter and volume growth in our small sample. As this parameter previously has been shown to predict rupture, it is promising as a future clinical predictor for AAA progression and outcome. Our results also suggest a role for the ILT in AAA expansion since both the mean stress and volume of the ILT correlated with AAA volume growth.

Abstract 489: Peak Wall Stress and Rupture Risk of Abdominal Aortic Aneurysms Are Not Influenced by Age

OBJECTIVES: Older patients with Abdominal Aortic Aneurysms (AAA) face higher perioperative mortality and, according to a recent meta-analysis, a higher risk of rupture. The relationship between age and AAA biomechanics, however, has not been studied previously. Our aim was to investigate age dependent differences in peak wall stress (PWS) and peak wall rupture risk (PWRR = wall stress / wall strength), as estimated by finite element modeling (FEM).

METHODS: 80 patients, 52-88 years old with AAA diameters between 40 and 60 mm, who had undergone computed tomography angiography (CT-A), were included. PWS and PWRR were estimated, by FEM, based on patient demographics and CT-A-derived AAA geometry, including the intraluminal thrombus (ILT). Three diameter matched age groups (≤65, 66-75 and ≥76 years old) were compared with respect to ILT-volume, PWS and PWRR with ANOVA and Kruskal-Wallis test. Correlation was tested with Spearman’s rank correlation coefficient.

RESULTS: All age groups had similar diameters (53.2 vs 52.8 vs 54.6 mm, P=0.44). No associations between age and biomechanical parameters were found. Differences in PWS (200.9 vs 199.0 vs 198.3 kPa, P=0.98) and PWRR (0.39 vs 0.37 vs 0.38 P=0.74) between age groups were small and non-significant. No correlation existed between age and PWS (r=0.018, P=0.88) or PWRR (r=0.031, P = 0.78). In the whole cohort, women had a significantly higher PWRR than men had (0.48 vs 0.35, P<0.0001).

CONCLUSIONS: Biomechanical parameters estimated by FEM do not differ between different age groups. However, as previously shown, women have a higher rupture risk which may explain the correlation between age and risk of rupture found in recent studies, since more women are found in the higher age groups.

Abstract 103: Biomechanical Rupture Risk Assessment in Patients with Abdominal Aortic Aneurysms: Introducing Rupture Risk Equivalent Diameter

OBJECTIVES: Finite Element (FE) Analysis has been used to estimate Peak Wall Stress (PWS) and Peak Wall Rupture Risk (PWRR) of Abdominal Aortic Aneurysms (AAA). However, these values are not familiar for clinicians. The aim of this study was to introduce a patient specific and clinically applicable biomechanical rupture risk assessment tool that would be easy for Vascular Surgeons to comprehend.

METHODS: Clinical data(gender, age, smoking, chronic obstructive lung disease, mean arterial pressure, family history) and CT images were retrospectively gathered from 200(142 male, 44 female) non ruptured AAA patients from 4 different hospitals in Sweden, Belgium and Germany. FE models were created using the diagnostics system A4clinics (VASCOPS, Austria) and the maximum diameter, PWS and PWRR was calculated automatically. Statistical analysis was performed with Mathematica (Wolfram Research Inc, USA).

RESULTS: The maximum diameter was normally distributed in males and females and no difference was found between PWS levels in men and women (p=0.091) but the PWRR was higher in women (p=0.005). PWS increased in a linear fashion and PWRR exponentially with diameter. We then related PWRR to the maximum diameters of patients and calculated the Rupture Risk Equvialent Diameter (RRED) as shown in the figure. A PWRR of 0.48 corresponds to an RRED of 55 millimeters. We also found that a RRED of 55 mm corresponds to the rupture risk in a male with a maximum AAA diameter of 58 mm, but in a female the corresponding maximum diameter was only 46mm.

CONCLUSIONS: Biomechanical AAA rupture risk assessment integrates risk based on clinical parameters and data from CT images. The RRED expresses this information as a diameter that is comprehensible for clinicians.

Steroids in rhinoplasty

A prospective double-blind randomized pilot study was performed to test the benefits of steroids versus placebo in controlling edema and ecchymosis in rhinoplasty within the immediate postoperative period. Thirty consecutive patients who underwent rhinoplasty with osteotomies were entered into the study. Sixteen patients received 10 mg of intravenous dexamethasone before the procedure and 14 patients received placebo. All rhinoplasties were performed by residents under the supervision of staff otolaryngologists. A 4-point scale was used to assess the extent of periorbital edema and ecchymosis at 24 hours postoperatively. A one-time bolus of 10 mg of dexamethasone was beneficial in decreasing edema and ecchymosis in rhinoplasty. This benefit was demonstrated statistically (p less than .005). No complications were attributed to the administration of dexamethasone.

Immunological relationships among lactic dehydrogenases in the genera Lactobacillus and Leuconostoc

Antisera were prepared against pure nicotinamide adenine dinucleotide-dependent d-lactic dehydrogenases of Lactobacillus leichmannii, L. jensenii, and L. fermenti. When tested against these three antisera, crude extracts of almost all species of Lactobacillus containing a d-lactic dehydrogenase give cross-reactions. Extensive pairwise comparisons between cross-reacting crude extracts by double diffusion experiments permit the recognition of groups of identical antigenic specificity among the lactic dehydrogenases of the various nomenspecies of Lactobacillus. The same groups are revealed by each of the three antisera. By analyses of spur formation, the groups of identical antigenic specificity can be arranged in order of decreasing similarity to the homologous d-lactic dehydrogenase used as the reference point. From the combined results obtained with the three antisera, a map of the antigenic relationships among the d-lactic dehydrogenases of lactobacilli can be constructed. Microcomplement fixation experiments with two of the three anti-d-lactic dehydrogenases antisera support the conclusions drawn from double diffusion experiments and provide a quantitative estimation of the antigenic relationships among the various d-lactic dehydrogenases. An antiserum was also prepared against the pure l-lactic dehydrogenase of L. acidophilus group III. It cross-reacts with extracts of almost all lactobacilli containing an l-lactic dehydrogenase. With respect to species that contain both d- and l-lactic dehydrogenases, this antiserum reveals the same groups of identical antigenic specificity as do the antisera directed against d-lactic dehydrogenases. Other than the genus Lactobacillus, only extracts of Leuconostoc cross-react with anti-d-lactic dehydrogenase. No extrageneric cross-reactions were obtained with the anti-l-lactic dehydrogenase.

Comparative immunological studies of two Pseudomonas enzymes

Crystalline preparations of muconate lactonizing enzyme and muconolactone isomerase, two inducible enzymes that catalyze successive steps in the catechol branch of the beta-ketoadipate pathway, were used to prepare antisera. Both enzymes were isolated from a strain of Pseudomonas putida biotype A. The antisera did not cross-react with enzymes of the same bacterial strain that catalyze the chemically analogous steps in the protocatechuate branch of the beta-ketoadipate pathway, carboxymuconate lactonizing enzyme and carboxymuconolactone decarboxylase. The antisera gave heterologous cross-reactions of varying intensities with the muconate lactonizing enzymes and muconolactone isomerases of P. putida biotype B, P. aeruginosa, P. stutzeri, and all biotypes of P. fluorescens, but did not cross-react with the isofunctional enzymes of P. acidovorans, of P. multivorans, and of two bacterial species that belong to other genera. The evolutionary and taxonomic implications of the findings are discussed.