Curvature effect on hemodynamic conditions at the inner bend of the carotid siphon and its relation to aneurysm formation

Although high-impact hemodynamic forces are thought to lead to cerebral aneurysmal change, little is known about the aneurysm formation on the inner aspect of vascular bends such as the internal carotid artery (ICA) siphon where wall shear stress (WSS) is expected to be low. This study evaluates the effect of vessel curvature and hemodynamics on aneurysm formation along the inner carotid siphon. Catheter 3D-rotational angiographic volumes of 35 ICA (10 aneurysms, 25 controls) were evaluated in 3D for radius of curvature and peak curvature of the siphon bend, followed by univariate statistical analysis. Computational fluid dynamic (CFD) simulations were performed on patient-derived models after aneurysm removal and on synthetic variants of increasing curvature. Peak focal siphon curvature was significantly higher in aneurysm bearing ICAs (0.36±0.045 vs. 0.30±0.048 mm⁻¹, p=0.003), with no difference in global radius of curvature (p=0.36). In CFD simulations, increasing parametric curvature tightness (from 5 to 3 mm radius) resulted in dramatic increase of WSS and WSS gradient magnitude (WSSG) on the inner wall of the bend. In patient-derived data, the location of aneurysms coincided with regions of low WSS (<4 Pa) flanked by high WSS and WSSG peaks. WSS peaks correlated with the aneurysm neck. In contrast, control siphon bends displayed low, almost constant, WSS and WSSG profiles with little spatial variation. High bend curvature induces dynamically fluctuating high proximal WSS and WSSG followed by regions of flow stasis and recirculation, leading to local conditions known to induce destructive vessel wall remodeling and aneurysmal initiation.     

Expression and analysis of green fluorescent proteins in human embryonic kidney cells by capillary electrophoresis

The green fluorescent protein (GFP) has attracted much interest as a reporter for gene expression. In this paper, application of capillary electrophoresis with laser-induced fluorescent (CE-LIF) for quantitation of green fluorescence protein in cellular extracts and single cells is investigated. The S65T mutant form of GFP protein was successfully expressed in human embryonic kidney (HEK293) cells, and its production was confirmed by fluorescence microscopy and CE-LIF. The mass limit of detection for the mutant S65T was 5.3 x 10(-20) mol, which was better than that for the wild-type GFP by a factor of six. Detection of a small amount of GFP is difficult by conventional techniques such as fluorescent microscopy due to interference from cell autofluorescence at low GFP concentrations. The HEK293 cells were transfected with the GFP plasmid that produced S65T-GFP. Transient production of S65T protein was detected 2 h after the transfection and reached a maximum after 48 h. The protein concentration began to decrease significantly after 96 h. Single cell analysis of HEK293 cells after transfection with GFP plasmid indicate a nonuniform production of S65T-GFP protein among cells.     

A multiscale synthesis: characterizing acute cartilage failure under an aggregate tibiofemoral joint loading

Biomechanics and Modeling in Mechanobiology - Knee articular cartilage is characterized by a complex mechanical behavior, posing a challenge to develop an efficient and precise model. We argue that...     

Evidence of sibling species between two host-associated populations of brown planthopper, N. lugens (stål) (Homoptera: Delphacidea) complex based on morphology and host–plant relationship studies

Morphological and host–plant relationship studies were conducted to differentiate two sympatric populations of brown planthopper (BPH), Nilaparvata lugens, one from rice (Oryza sativa) and the other from Leersia hexandra, a weed grass. In morphometric studies based on esterase activities, an UPGMA dendrogram using 17 quantitative morphological characters, including stridulatory organs (courtship signal-producing organs) between two sympatric populations of N. lugens, one from rice and the other from L. hexandra, a weed grass revealed that both populations were separated from each other. An out-group, N. bakeri, was found to be completely different from the two sympatric populations of N. lugens. Rice plants were best suited for the establishment of the rice-infesting population, and L. hexandra was a favourable host for the Leersia-infesting population. The individuals derived from one host did not thrive on the other host, as shown by a significant reduction in survival and nymphal development, ovipositional preferences, ovipositional response, and egg hatchability. Therefore, morphological and host–plant relationship studies indicate that rice-associated population with high esterase activities and L. heaxandra-associated population with low esterase activities are two closely related sibling species.     

Anchorage-independent growth of murine melanoma in serum-less media is dependent on insulin or melanocyte-stimulating hormone

α-Melanocyte-stimulating hormone (MSH) is known to stimulate melanogenesis in murine melanoma, particularly in Cloudman S-91 melanoma cells. The effects of MSH and insulin on the proliferation of S91 murine melanoma cells have aroused controversy; in various reports, both hormones have been reported to either stimulate or inhibit murine melanoma growth. In our studies both MSH and insulin stimulated the colony-forming ability and the proliferative capacity of S-91 murine melanoma cells grown in soft agar with either serum-supplemented or serum-less medium. Unless insulin and/or MSH were present, Cloudman S-91 melanoma cells failed to clone in soft agar. The insulin effect was greater than that of MSH, and was more pronounced in serum-less than in serum-supplemented medium. The concurrent treatment of S91 melanoma cells with both MSH and insulin resulted in a greater increase in the total number of colonies formed than caused by treatment with either hormone alone. The combined MSH-insulin stimulation of anchorage-independent growth was specific, since the effect could not be mimicked by epidermal growth factor (EGF), gonadotropin-releasing hormone (GRH), luteinizing hormone (LH), nerve growth factor (NGF) or platelet-derived growth factor (PDGF). Therefore, MSH and insulin may be specific growth factors for murine melanoma cells.