Dynamic Motions of Ligands around the Metal Centers Afford a Fidget Spinner-Type AIE Luminogen.

A new type of aggregation-induced emission (AIE) luminogen containing a dimeric metal fragment and two or three phthalazine ligands is described, which shows dynamic motions of ligands around the metal centers in solution. Based on the variable-temperature and EXSY NMR spectroscopy data, X-ray crystallography structures, and computational results, three different pathways (i.e., reversible exchange with haptotropic shifts, circulation of ligands around the dimeric metal fragment, and walking on the spot of ligands on the metal centers) were considered for this dynamic behavior. Restriction of these dynamic processes in the aggregate forms of the compounds (in H2O/CH3CN solvent mixtures) contributes to their AIE. DFT calculations and NMR analysis showed that bright excited states for these molecules are not localized on isolated molecules, and the emission of them stemmed from π-dimers or π-oligomers. The morphologies and the mode of associations in the solvent mixtures were determined by using transmission electron microscopy (TEM) and concentration-dependent NMR spectroscopy. The computational results showed the presence of a conical intersection (CI) between the S0 and S1 excited state, which provides an accessible pathway for nonradiative decay in these systems.

Prevalence of hepatitis C virus genotypes in HIV positive patients referring to the consultation center for behavioral diseases, Sanandaj, Iran.

BACKGROUND AND OBJECTIVES: Co-infection of hepatitis C virus (HCV) with human immunodeficiency virus (HIV) is increasing due to similar transmission pathways. Chronic HCV infection is the most common complication among HIV-infected individuals. Information on the frequency of HCV infection on Iranian HIV-infected individuals is scarce. The aim of this study was the detection of HCV prevalence and genotypes among HIV-infected people in Sanandaj, Iran. MATERIALS AND METHODS: In this cross-sectional study, whole blood samples were taken from 185 HIV positive individuals referring to Consultation Center for Behavioral Diseases, Sanandaj, Iran. The ELISA test was done on samples for anti-HCV antibodies. RNA was extracted from only anti-HCV antibody positive samples. An RT-PCR test was conducted to detect HCV RNA. Genotypes of HCV were detected by melting curve analysis by specific primers and probes. Test results and demographic information were analyzed by SPSS software. RESULTS: The mean age of individuals was 39.3 ± 9.4 years. Out of 185 individuals 99 (53.5%) were positive for anti-HCV antibodies. Out of 99 antibody positive individuals, 44 had HCV RNA. Among 44 RNA positive individuals, genotypes and subtypes of HCV were as 26 (59.1%) 1a, 17 (38.6%) 3a and one (2.2%) 4. There was a significant association between anti-HCV antibody and demographic variables including, age, gender, occupation, and CD4+ T-cell count (p = 0.0001). CONCLUSION: The present study reveals that HIV/HCV co-infection is high in the study population. It is recommended similar studies should be done in other HIV infected populations for management of HIV/HCV co-infection.

Novel Hemi-Staple for the Fusionless Correction of Pediatric Scoliosis: Influence on Intervertebral Disks and Growth Plates in a Porcine Model.

STUDY DESIGN: In vivo porcine model utilized to evaluate the influence of an intravertebral fusionless growth modulating device (hemi-staple) on intervertebral disks and growth plates. OBJECTIVE: To evaluate the radiographic and histologic changes in disks and growth plates with the purpose of measuring influence of the explored hemi-staple. SUMMARY OF BACKGROUND DATA: Fusionless growth modulation for the early treatment of scoliosis should insure the long-term viability of the intervertebral disk and successfully reduce or arrest local growth. A novel hemi-staple that proved effective in the control of coronal spinal alignment warranted further analyses of its influence on the disk health and growth-plate morphology. METHODS: A hemi-staple that inhibited local vertebral growth exclusive of the disk was introduced over T5-T8 in 4 immature pigs (16 vertebrae; experimental), whereas 3 underwent surgery without instrumentation (sham) and 2 had no intervention (control). Three-month follow-up before animal euthanasia provided radiographic (disk height and health) and histologic (growth plate morphology, disk health, and type X collagen distribution) analyses. RESULTS: No postoperative complications were experienced. Radiographic data returned inverse disk wedging (greater disk height adjacent to device, 2.6±0.7 mm compared with the noninstrumented side, 1.8±0.5 mm) in experimental segments and suggested disk viability. Histologic data confirmed device growth modulation through significant local reduction of growth plate hypertrophic zone (125.64±16.61 µm and 61.16±8.25 µm in noninstrumented and instrumented sections, respectively) and cell height (16.14±1.87 µm and 9.22±1.57 µm in noninstrumented and instrumented sections, respectively). A variability of disk health, dependant of device insertion location, was observed. Type X collagen was consistently identified in experimental growth plates and absent from intervertebral disks. CONCLUSIONS: Hemi-staples decreased growth plate hypertrophic zone and cell height, and, depending on device insertion site, showed positive signs of disk health sustainability. Spinal growth modulation achieved exclusive of disk compression, as practiced by this method, offers unique advantages over other fusionless techniques. This technique may provide a suitable and attractive alternative for the early treatment of idiopathic scoliosis.

Stress relaxation of swine growth plate in semi-confined compression: depth dependent tissue deformational behavior versus extracellular matrix composition and collagen fiber organization.

Mechanical environment is one of the regulating factors involved in the process of longitudinal bone growth. Non-physiological compressive loading can lead to infantile and juvenile musculoskeletal deformities particularly during growth spurt. We hypothesized that tissue mechanical behavior in sub-regions (reserve, proliferative and hypertrophic zones) of the growth plate is related to its collagen and proteoglycan content as well as its collagen fiber orientation. To characterize the strain distribution through growth plate thickness and to evaluate biochemical content and collagen fiber organization of the three histological zones of growth plate tissue. Distal ulnar growth plate samples (N = 29) from 4-week old pigs were analyzed histologically for collagen fiber organization (N = 7) or average zonal thickness (N = 8), or trimmed into the three average zones, based on the estimated thickness of each histological zone, for biochemical analysis of water, collagen and glycosaminoglycan content (N = 7). Other samples (N = 7) were tested in semi-confined compression under 10% compressive strain. Digital images of the fluorescently labeled nuclei were concomitantly acquired by confocal microscopy before loading and after tissue relaxation. Strain fields were subsequently calculated using a custom-designed 2D digital image correlation algorithm. Depth-dependent compressive strain patterns and collagen content were observed. The proliferative and hypertrophic zone developed the highest axial and transverse strains, respectively, under compression compared to the reserve zone, in which the lowest axial and transverse strains arose. The collagen content per wet mass was significantly lower in the proliferative and hypertrophic zones compared to the reserve zone, and all three zones had similar glycosaminoglycan and water content.Polarized light microscopy showed that collagen fibers were mainly organized horizontally in the reserve zone and vertically aligned with the growth direction in the proliferative and hypertrophic zones. Higher strains were developed in growth plate areas (proliferative and hypertrophic) composed of lower collagen content and of vertical collagen fiber organization. The stiffer reserve zone, with its higher collagen content and collagen fibers oriented to restrain lateral expansion under compression, could play a greater role of mechanical support compared to the proliferative and hypertrophic zones, which could be more susceptible to be involved in an abnormal growth process.

Three-dimensional in situ zonal morphology of viable growth plate chondrocytes: a confocal microscopy study.

Longitudinal growth, occurring in growth plates with structurally distinct zones, has clinical implications in the treatment of progressive skeletal deformities. This study documents the three-dimensional morphology of chondrocytes within histological zones of growth plate using confocal microscopy combined with fluorescent labeling techniques. Three-dimensional reconstruction of Calcein AM-labeled chondrocytes was made from stacks of confocal images recorded in situ from 4-week-old swine growth plates. Three-dimensional quantitative morphological measurements were further performed and compared at both tissue and cell levels. Chondrocyte volume and surface area increased about five- and threefold, respectively, approaching the chondro-osseous junction from the pool of reserve cells. Chondrocytes from the proliferative zone were the most discoidal cells (sphericity of 0.81 ± 0.06) among three histological zones. Minimum and maximum cell/matrix volume ratios were identified in the reserve (11.0 ± 2.2) and proliferative zones (16.8 ± 3.0), respectively. Evaluated parameters revealed the heterogeneous and zone-dependent morphological state of the growth plate. Tissue and cellular morphology may have noteworthy contribution to the growth plate behavior during growth process. The ability to obtain in situ cell morphometry and monitor the changes in the growth direction could improve our understanding of the mechanisms through which abnormal growth is triggered.

Tissue and cellular morphological changes in growth plate explants under compression.

The mechanisms by which mechanical loading may alter bone development within growth plates are still poorly understood. However, several growth plate cell or tissue morphological parameters are associated with both normal and mechanically modulated bone growth rates. The aim of this study was to quantify in situ the three-dimensional morphology of growth plate explants under compression at both cell and tissue levels. Growth plates were dissected from ulnae of immature swine and tested under 15% compressive strain. Confocal microscopy was used to image fluorescently labeled chondrocytes in the three growth plate zones before and after compression. Quantitative morphological analyses at both cell (volume, surface area, sphericity, minor/major radii) and tissue (cell/matrix volume ratio) levels were performed. Greater chondrocyte bulk strains (volume decrease normalized to the initial cell volume) were found in the proliferative (35.4%) and hypertrophic (41.7%) zones, with lower chondrocyte bulk strains (24.7%) in the reserve zone. Following compression, the cell/matrix volume ratio decreased in the reserve and hypertrophic zones by 24.3% and 22.6%, respectively, whereas it increased by 35.9% in the proliferative zone. The 15% strain applied on growth plate explants revealed zone-dependent deformational states at both tissue and cell levels. Variations in the mechanical response of the chondrocytes from different zones could be related to significant inhomogeneities in growth plate zonal mechanical properties. The ability to obtain in situ cell morphometry and monitor the changes under compression will contribute to a better understanding of mechanisms through which abnormal growth can be triggered.

Effects of cyclic stretch waveform on endothelial cell morphology using fractal analysis.

Endothelial cells are remodeled when subjected to cyclic loading. Previous in vitro studies have indicated that frequency, strain amplitude, and duration are determinants of endothelial cell morphology, when cells are subjected to cyclic strain. In addition to those parameters, the current study investigated the effects of strain waveform on morphology of cultured endothelial cells quantified by fractal and topological analyses. Cultured endothelial cells were subjected to cyclic stretch by a designed device, and cellular images before and after tests were obtained. Fractal and topological parameters were calculated by development of an image-processing code. Tests were performed for different load waveforms. Results indicated cellular alignment by application of cyclic stretch. By alteration of load waveform, statistically significant differences between cell morphology of test groups were observed. Such differences are more prominent when load cycles are elevated. The endothelial cell remodeling was optimized when the applied cyclic load waveform was similar to blood pressure waveform. Effects of load waveform on cell morphology are influenced by alterations in load amplitude and frequency. It is concluded that load waveform is a determinant of endothelial morphology in addition to amplitude and frequency, and such effect is elevated by increase of load cycles. Due to high correlation between fractal and topological analyses, it is recommended that fractal analysis can be used as a proper method for evaluation of alteration in cell morphology and tissue structure caused by application of external stimuli such as mechanical loading.

Topological remodeling of cultured endothelial cells by characterized cyclic strains.

Evaluation of mechanical environment on cellular function is a major field of study in cellular engineering. Endothelial cells lining the entire vascular lumen are subjected to pulsatile blood pressure and flow. Mechanical stresses caused by such forces determine function of arteries and their remodeling. Critical values of mechanical stresses contribute to endothelial damage, plaque formation and atherosclerosis. A device to impose cyclic strain on cultured cells inside an incubator was designed and manufactured operating with different load amplitudes, frequencies, numbers of cycles and ratios of extension to relaxation. Endothelial cells cultured on collagen coated silicon scaffolds were subjected to cyclic loading. Effects of mechanical loading on cell morphology were quantified using image processing methods. Results showed change in cell orientation from a randomly oriented before the test up to 80 degrees alignment from load axis after loading. Endothelial cells were elongated with shape index reductions up to 47% after cyclic stretch. By increase of strain amplitude, loading frequency and number of cycles, significant decrease in shape index and significant increase in orientation angle were observed. Change of load waveform similar to arterial pulse pressure waveform resulted in alteration of cell alignment with 9.7% decrease in shape index, and 10.8% increase in orientation angle. Results of cyclic loading tests in a disturbed environment with elevated PH showed lack of remodeling. It was concluded that tensile loading of endothelial cells influences cell morphology and alignment, a mechanism for structural regulation, functional adaptation and remodeling. Disturbed environment results in endothelial dysfunction and injury.