Magnetic Resonance Elastography Methodology for the Evaluation of Tissue Engineered Construct Growth

Traditional mechanical testing often results in the destruction of the sample, and in the case of long term tissue engineered construct studies, the use of destructive assessment is not acceptable. A proposed alternative is the use of an imaging process called magnetic resonance elastography. Elastography is a nondestructive method for determining the engineered outcome by measuring local mechanical property values (i.e., complex shear modulus), which are essential markers for identifying the structure and functionality of a tissue. As a noninvasive means for evaluation, the monitoring of engineered constructs with imaging modalities such as magnetic resonance imaging (MRI) has seen increasing interest in the past decade¹. For example, the magnetic resonance (MR) techniques of diffusion and relaxometry have been able to characterize the changes in chemical and physical properties during engineered tissue development². The method proposed in the following protocol uses microscopic magnetic resonance elastography (μMRE) as a noninvasive MR based technique for measuring the mechanical properties of small soft tissues³. MRE is achieved by coupling a sonic mechanical actuator with the tissue of interest and recording the shear wave propagation with an MR scanner⁴. Recently, μMRE has been applied in tissue engineering to acquire essential growth information that is traditionally measured using destructive mechanical macroscopic techniques⁵. In the following procedure, elastography is achieved through the imaging of engineered constructs with a modified Hahn spin-echo sequence coupled with a mechanical actuator. As shown in Figure 1, the modified sequence synchronizes image acquisition with the transmission of external shear waves; subsequently, the motion is sensitized through the use of oscillating bipolar pairs. Following collection of images with positive and negative motion sensitization, complex division of the data produce a shear wave image. Then, the image is assessed using an inversion algorithm to generate a shear stiffness map⁶. The resulting measurements at each voxel have been shown to strongly correlate (R²>0.9914) with data collected using dynamic mechanical analysis⁷. In this study, elastography is integrated into the tissue development process for monitoring human mesenchymal stem cell (hMSC) differentiation into adipogenic and osteogenic constructs as shown in Figure 2.     

Interaction of MTHFR 1298C with ACE D allele augments the risk of diabetic nephropathy in Western Iran

The aim of the current study was to examine the influence of interaction between polymorphisms of methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C with angiotensin converting enzyme insertion/deletion (ACE I/D) polymorphism on the risk of diabetic nephropathy (DN). In a case control study using polymerase chain reaction (PCR)- and PCR-restriction fragment length polymorphism (RFLP), the presence of three polymorphisms in 140 patients with type 2 diabetes mellitus (T2DM) with nephropathy including patients with micro- and macro-albuminuria and 72 patients with normoalbuminuria from Western Iran were investigated. In the presence of both MTHFR 677 T and ACE D alleles, there was a trend toward increased risk of DN 2.68-fold (p=0.054). The possession of both MTHFR 677 T and ACE D alleles increased the risk of macro-albuminuria four times (p=0.035). The concomitant presence of both MTHFR 1298 C and ACE D alleles increased the risk of macro-albuminuria 7.8-fold (p=0.012). In addition, the risk of progression from micro- to macro-albuminuria in the presence of both alleles tended to be increased (4.1-fold, p=0.09). Our study for the first time demonstrated a synergistic effect between ACE I/D with either MTHFR C677T or A1298C polymorphism on the increased risk of DN among patients with T2DM. We found that MTHFR 1298 C strongly interacts with the ACE D allele and augments the risk of DN in our population.     

A comparison between sequential therapy and a modified bismuth-based quadruple therapy for Helicobacter pylori eradication in Iran: a randomized clinical trial

Background: Sequential regimens have been recently reported to be superior to the standard triple therapies in Helicobacter pylori eradication, but most of these studies were performed in Europe and data from developing countries are lacking. So we designed a study to compare a sequential regimen with a bismuth‐based quadruple therapy that contains a short course of furazolidone, in Iran. Methods: Two hundred and ninety‐six patients with duodenal ulcer and naïve H. pylori infection were randomized into two groups: 148 patients received (PAB‐F) pantoprazole (40 mg‐bid), amoxicillin (1 g‐bid), and bismuth subcitrate (240 mg‐bid) for 2 weeks and furazolidone (200 mg‐bid) just during the first week. And 148 patients received (PA‐CT) pantoprazole (40 mg‐bid) for 10 days, amoxicillin (1 g‐bid) for the first 5 days, and clarithromycin (500 mg‐bid) plus tinidazole (500 mg‐bid) just during the second 5 days. C¹⁴‐urea breath test was performed 8 weeks after the treatment. Results: Two hundred and sixty‐one patients completed the study (137 patients in the PA‐CT and 124 in the PAB‐F group). The results were not statistically different between the two groups in the eradication rates and the severity of side effects. The intention to treat eradication rate was 80.4% in the PAB‐F group and 83.7% in the PA‐CT group. Per‐protocol eradication rates were 88.7% and 89.1%, respectively. Conclusion: Because the two regimens showed acceptable and similar abilities in H. pylori eradication and because of much higher cost of clarithromycin in Iran, the furazolidone containing regimen seems to be superior. Further modifications of sequential therapies are needed to make them ideal regimens in developing countries.     

Cellular infiltration on nanofibrous scaffolds using a modified electrospinning technique

Electrospinning is currently used to fabricate nanofibrous scaffolds for tissue engineering applications. The major problem of these scaffolds is their intrinsically two-dimensional nature which inhibits cellular migration and in-growth. In this study, we have introduced a modified setup of electrospinning to produce three-dimensional nanofibrous scaffolds which allows improved infiltration of cells. An array of focused halogen light bulbs was used to localize the heat in the path of electrospun jet near the collector. The fabricated mats were then seeded with cells in order to evaluate migration and infiltration. After 14 days of culture, a homogenous distribution of cells was observed throughout the scaffolds and showed the three-dimensional architecture of nanofibrous mats. By this novel and simple setup, the prepared electrospun mats will allow the seeded cells to obtain a three-dimensional arrangement which is ideal for tissue engineering applications.     

Biological traits and life table parameters of variegated lady beetle, <Emphasis Type="Italic">Hippodamia variegata</Emphasis> (Coleoptera: Coccinellidae) on three aphid species

The aphidophagous ladybird beetle, Hippodamia variegata (Goeze) (Coleoptera: Coccinellidae), is a dominant predator in various crop systems. Its life history was studied when fed on three aphid prey, viz. Aphis gossypii Glover, Aphis fabae Scopoli and Macrosiphum rosae (L.), under laboratory conditions, 25 ± 1 °C, 65 ± 5 % RH and a photoperiod of 16L:8D. The immature development period was shortest (15.2 days) when A. gossypii was used as prey and longest (18.9 days) on A. fabae. Adult coccinellids had the shortest longevity on A. fabae (64.8 days). The higher and lower mean daily fecundity was recorded for A. fabae (12.4 eggs) and M. rosae (6.2 eggs), respectively. The highest (291.0 eggs) and lowest (183.2 eggs) net reproduction rates (R ₀) were observed on A. fabae and M. rosae, respectively. Mean generation time (T) on rose aphid was significantly longer (33.4 days) than on the two other preys. The intrinsic rate of increase (r _m) was affected by the R ₀ value, and it was highest on A. fabae (0.183) and lowest on M. rosae (0.156). Based on r _m as an index of suitability of prey species, A. fabae was the most suitable prey for H. variegata. Our finding may provide basic information for developing aphid biological control programs.     

Analytical approximations for the amplitude and period of a relaxation oscillator

Background  

Analysis and design of complex systems benefit from mathematically tractable models, which are often derived by approximating a nonlinear system with an effective equivalent linear system. Biological oscillators with coupled positive and negative feedback loops, termed hysteresis or relaxation oscillators, are an important class of nonlinear systems and have been the subject of comprehensive computational studies. Analytical approximations have identified criteria for sustained oscillations, but have not linked the observed period and phase to compact formulas involving underlying molecular parameters.     

Metastatic follicular thyroid carcinoma diagnosed by fine needle aspiration cytology: a report of 3 cases

BACKGROUND: Follicular thyroid carcinomas (FTCs) usually have a benign clinical course, with an excellent long-term prognosis and a propensity for vascular invasion. The most common sites of metastases are lung and bone. Only a few reports are available on fine needle aspiration biopsy findings from metastatic lesions of FTC. CASES: A 68-year-old man presented with a thyroid mass and skin nodule on the scalp. Skin nodule aspiration revealed metastatic FTC. A 52-year-old woman and 60-year-old man were investigated for chronic anemia. As part of the routine investigation, bone marrow aspiration and biopsy were performed from the posterior iliac crest and diagnosed as metastatic FTC. Further questioning revealed that the patients had undergone thyroidectomy 10 and 13 years earlier. The aspiration material in all 3 cases revealed epithelial cell clusters with marginal (fire-flare) vacuoles. CONCLUSION: Cytologic diagnosis of metastatic FTC has been reported rarely. Marginal (fire-flare) vacuoles aid in making the diagnosis of metastatic FTC.     

Colored extrinsic fluctuations and stochastic gene expression

Stochasticity is both exploited and controlled by cells. Although the intrinsic stochasticity inherent in biochemistry is relatively well understood, cellular variation, or ‘noise’, is predominantly generated by interactions of the system of interest with other stochastic systems in the cell or its environment. Such extrinsic fluctuations are nonspecific, affecting many system components, and have a substantial lifetime, comparable to the cell cycle (they are ‘colored’). Here, we extend the standard stochastic simulation algorithm to include extrinsic fluctuations. We show that these fluctuations affect mean protein numbers and intrinsic noise, can speed up typical network response times, and can explain trends in high‐throughput measurements of variation. If extrinsic fluctuations in two components of the network are correlated, they may combine constructively (amplifying each other) or destructively (attenuating each other). Consequently, we predict that incoherent feedforward loops attenuate stochasticity, while coherent feedforwards amplify it. Our results demonstrate that both the timescales of extrinsic fluctuations and their nonspecificity substantially affect the function and performance of biochemical networks.     

Concerted auto-regulation in yeast endosomal t-SNAREs

In yeast, the assembly of the target (t)-SNAREs [Tlg2p/Tlg1p,Vti1p] and [Pep12p/Tlg1p,Vti1p] with the vesicular (v)-SNARE Snc2p promotes endocytic fusion. Here, selected mutations and truncations of SNARE proteins were tested in an in vitro fusion assay to identify potential regulatory regions in these proteins, and two distinct regions were found. The first is represented by the combined effect of the three t-SNARE N-terminal regions and the second is located within the Tlg1p SNARE motif. These internal controls provide a potential mechanism to enable SNARE-dependent fusion to be regulated.