Anterior cruciate ligament reconstruction: Magnetic resonance imaging and factors influencing outcome

Purpose

This study was conducted to determine the magnetic resonance imaging (MRI) findings in cases of complications following anterior cruciate ligament (ACL) reconstructive surgery, and to correlate these complications with their possible etiological factors based on clinical and radiological criteria.

Methods

The study included 48 symptomatic patients (40 males and 8 females) after arthroscopic ACL reconstruction in the period between 2006 and 2008. Clinical evaluation of the patients was performed using the International Knee Documentation Committee scoring system (IKDC). MRI was performed using 1.5 T dedicated system and a standard imaging protocol. The scans were then reviewed by two senior radiologists for the assessment of integrity of the reconstructed ligament and the presence of related complications. The findings were then analyzed and correlated with the clinical evaluation.

Results

Tunnel widening was the most common MRI finding seen, as it was present in 42 patients (87.5%). The detected post reconstructive complications encountered in our patients included graft tear in 34 patients (70.83%), impingement in 12 patients (25%), osteoarthritis in six patients (12.5%), cystic degeneration in two patients (4.16%), and Cyclops lesion in two patients (4.16%).

Conclusions

MRI is a valuable imaging modality for assessment of post ACL reconstructive complications, as it is useful in demonstrating tunnel positioning, graft integrity and other soft tissue structures of the knee. It also helps in identifying possible underlying causes and predisposing factors for ACL graft failure.     

Cerebral myogenic reactivity and blood flow in type 2 diabetic rats: role of peroxynitrite in hypoxia-mediated loss of myogenic tone

Dysregulation of cerebral vascular function and, ultimately, cerebral blood flow (CBF) may contribute to complications such as stroke and cognitive decline in diabetes. We hypothesized that 1) diabetes-mediated neurovascular and myogenic dysfunction impairs CBF and 2) under hypoxic conditions, cerebral vessels from diabetic rats lose myogenic properties because of peroxynitrite (ONOO(-))-mediated nitration of vascular smooth muscle (VSM) actin. Functional hyperemia, the ability of blood vessels to dilate upon neuronal stimulation, and myogenic tone of isolated middle cerebral arteries (MCAs) were assessed as indices of neurovascular and myogenic function, respectively, in 10- to 12-week control and type 2 diabetic Goto-Kakizaki rats. In addition, myogenic behavior of MCAs, nitrotyrosine (NY) levels, and VSM actin content were measured under normoxic and hypoxic [oxygen glucose deprivation (OGD)] conditions with and without the ONOO(-) decomposition catalyst 5,10,15,20-tetrakis(4-sulfonatophenyl) prophyrinato iron (III), chloride (FeTPPs). The percentage of myogenic tone was higher in diabetes, and forced dilation occurred at higher pressures. Functional hyperemia was impaired. Consistent with these findings, baseline CBF was lower in diabetes. OGD reduced the percentage of myogenic tone in both groups, and FeTPPs restored it only in diabetes. OGD increased VSM NY in both groups, and although FeTPPs restored basal levels, it did not correct the reduced filamentous/globular (F/G) actin ratio. Acute alterations in VSM ONOO(-) levels may contribute to hypoxic myogenic dysfunction, but this cannot be solely explained by the decreased F/G actin ratio due to actin nitration, and mechanisms may differ between control and diabetic animals. Our findings also demonstrate that diabetes alters the ability of cerebral vessels to regulate CBF under basal and hypoxic conditions.     

The virB operon is essential for lethality of Brucella microti in the Balb/c murine model of infection

In murine infections, Brucella microti exhibits an atypical and highly pathogenic behavior resulting in a mortality of 82%. In this study, the possible involvement of the virB type IV secretion system, a key virulence factor of Brucella sp., in this lethal phenotype was investigated. As previously described for B. suis, expression of the virB operon of B. microti was induced in acid minimal medium, partially mimicking intracellular environment. Early neutralization of cellular compartments abolished intracellular replication of B. microti, showing that acidity of the Brucella-containing vacuole is an essential trigger. A ΔvirB mutant of B. microti exhibited strong attenuation in murine and human macrophages in vitro. Interestingly, infection with this mutant was not lethal in Balb/c mice and lacked the typical intrasplenic peak at 3 days post-infection, hence demonstrating that lethality of B. microti in murine infection absolutely requires a functional virB operon.     

β-cell dysfunctional ERAD/ubiquitin/proteasome system in type 2 diabetes mediated by islet amyloid polypeptide-induced UCH-L1 deficiency

OBJECTIVE

The islet in type 2 diabetes is characterized by β-cell apoptosis, β-cell endoplasmic reticulum stress, and islet amyloid deposits derived from islet amyloid polypeptide (IAPP). Toxic oligomers of IAPP form intracellularly in β-cells in humans with type 2 diabetes, suggesting impaired clearance of misfolded proteins. In this study, we investigated whether human-IAPP (h-IAPP) disrupts the endoplasmic reticulum–associated degradation/ubiquitin/proteasome system.

RESEARCH DESIGN AND METHODS

We used pancreatic tissue from humans with and without type 2 diabetes, isolated islets from h-IAPP transgenic rats, isolated human islets, and INS 832/13 cells transduced with adenoviruses expressing either h-IAPP or a comparable expression of rodent-IAPP. Immunofluorescence and Western blotting were used to detect polyubiquitinated proteins and ubiquitin carboxyl-terminal hydrolase L1 (UCH-L1) protein levels. Proteasome activity was measured in isolated rat and human islets. UCH-L1 was knocked down by small-interfering RNA in INS 832/13 cells and apoptosis was evaluated.

RESULTS

We report accumulation of polyubiquinated proteins and UCH-L1 deficiency in β-cells of humans with type 2 diabetes. These findings were reproduced by expression of oligomeric h-IAPP but not soluble rat-IAPP. Downregulation of UCH-L1 expression and activity to reproduce that caused by h-IAPP in β-cells induced endoplasmic reticulum stress leading to apoptosis.

CONCLUSIONS

Our results indicate that defective protein degradation in β-cells in type 2 diabetes can, at least in part, be attributed to misfolded h-IAPP leading to UCH-L1 deficiency, which in turn further compromises β-cell viability.Type 2 diabetes is characterized by a progressive decline in β-cell function in the face of insulin resistance. Although the mechanisms underlying β-cell dysfunction are unknown, it is likely related to the presence of β-cell endoplasmic reticulum (ER) stress (1,2), increased β-cell apoptosis (3,4), and decreased β-cell mass (3,5). The islet in type 2 diabetes is also characterized by amyloid deposits derived from islet amyloid polypeptide (IAPP) (3). Insulin resistance, the most important risk factor for development of type 2 diabetes, induces increased β-cell expression of insulin but to an even greater extent IAPP (6,7).IAPP is a 37–amino acid peptide that is coexpressed and cosecreted with insulin (8). This peptide has the propensity to form amyloid fibrils in species at risk of spontaneously developing diabetes (e.g., nonhuman primates and cats). In contrast, in rodents, IAPP is not amyloidogenic because of proline residue substitutions, and rodents do not spontaneously develop type 2 diabetes with the islet morphology present in humans (9). However, increased expression of human-IAPP (h-IAPP) in rodents may lead to type 2 diabetes with islet pathology comparable to that in humans (10–14). Intracellular IAPP toxic oligomers and ER stress have been reported in β-cells of both humans with type 2 diabetes and rodents with high expression of h-IAPP (1,15,16).The ER is responsible for synthesis, folding, and maturation of proteins. It is endowed with a quality-control system that facilitates the recognition of misfolded proteins and targets them for degradation by the ubiquitin/proteasome system (17). Efficient removal of misfolded proteins by the endoplasmic reticulum–associated degradation (ERAD) is essential to protect cells from ER stress. This is accomplished by several distinct steps. First, if a protein fails quality control, it is removed from the ER by retrograde translocation. Second, multiple ubiquitin molecules are covalently attached to the targeted protein. Third, the polyubiquinated protein is relocated to the 26S proteasome. Fourth, the ubiquitin chains are removed from the misfolded protein by a deubiquitinating enzyme, and thus it is finally rendered available for degradation by the passage through the 26S proteasome (18).We recently reported that accumulation of polyubiquitinated proteins occurs in pancreatic islets of h-IAPP transgenic mice but not in mice with comparable transgenic expression of rodent-IAPP (r-IAPP) (16). This implies that increased expression of h-IAPP may interfere with the ERAD/ubiquitin/proteasome system, and thus contribute to β-cell ER stress. β-Cells in type 2 diabetes share many characteristics of neurons in neurodegenerative diseases, such as Alzheimer''s and Parkinson''s diseases, also characterized by protein misfolding, formation of toxic oligomers of locally expressed amyloidogenic proteins, and proteotoxicity prompting ER stress (9,19). These observations imply that the mechanisms that defend against accumulation of misfolded proteins may be disrupted in β-cells in type 2 diabetes as previously documented in neurodegenerative diseases (19–23). Of interest, impairment of the ubiquitin/proteasome pathway has been shown to contribute to neurotoxicity in some neurodegenerative diseases (20–23). In particular, deficiency in ubiquitin carboxyl-terminal hydrolase L1 (UCH-L1) has been observed in the brains of individuals with Alzheimer''s and Parkinson''s diseases (24). UCH-L1, a member of the deubiquinating enzyme family, is abundantly expressed in β-cells (25) and neurons (26). UCH-L1 is required to hydrolyze ubiquitin chains leading to both the release of protein targeted for degradation from the ubiquitin chain so that it can gain access to the proteasome and the generation of free monomeric ubiquitin that is then available for further cycles of the ubiquitin system. Thus, UCH-L1 deficiency impairs ubiquitin-dependent protein degradation and results in accumulation of highly ubiquitinated proteins (27–29).Given the parallels between neurons in neurodegenerative diseases and islets in type 2 diabetes, we hypothesized that the ERAD/ubiquitin/proteasome system is compromised in β-cells in type 2 diabetes. Further, we hypothesized that increased expression of amyloidogenic h-IAPP would reproduce this dysfunction. Finally, we postulated that the specific mechanism subserving the compromised ERAD/ubiquitin/proteasome system in β-cells in type 2 diabetes, and as a consequence of increased expression of h-IAPP, is decreased availability of UCH-L1.     

Differential responsiveness of humans with early-stage schistosomiasis haematobium to Schistosoma haematobium soluble adult-worm and egg antigens

Schoolchildren (7–8 years old) infected with Schistosoma haematobium were tested for lymphocyte proliferative responses, in vitro granuloma formation (IVGF), and cytokine release in T-cell Western assays and for serum antibody reactivity by enzyme-linked immunosorbent assay (ELISA) and immunoblotting against S. haematobium soluble adult-worm (SAWA) and egg (SEA) antigens. The lymphoproliferative response rate of individual subjects against 10 SAWA and 15 SEA electroseparated bands ranged from 0 to 33?% and from 11 to 66?%, respectively. The SAWA bands essentially failed to elicit significant IVGF, in contrast to the SEA bands, all of which were capable of inducing IVGF from peripheral blood mononuclear cells (PBMC) of 30–80?% of individual donors. The exclusive ability of SEA bands to induce IVGF could not be attributed to selective release of interleukin 2 (IL-2), IL-4, or interferon-gamma, as SEA and SAWA bands were capable of eliciting release of a similar array of cytokines in supernatants of 4-day PBMC cultures. The antibody response to SEA was stronger than that to SAWA, yet the proportion of SAWA bands binding humoral antibodies of individual donors was significantly larger than that observed for SEA. The study thus suggests that humans with early-stage S. haematobium infection respond poorly to SAWA but mount strong cellular immune responses to SEA that result in granuloma and antibody formation.     

MXene/Ag2CrO4 Nanocomposite as Supercapacitors Electrode

MXene/Ag₂CrO₄ nanocomposite was synthesized effectively by means of superficial low-cost co-precipitation technique in order to inspect its capacitive storage potential for supercapacitors. MXene was etched from MAX powder and Ag₂CrO₄ spinel was synthesized by an easy sol-gel scheme. X-Ray diffraction (XRD) revealed an addition in inter-planar spacing from 4.7 Å to 6.2 Å while Ag₂CrO₄ nanoparticles diffused in form of clusters over MXene layers that had been explored by scanning electron microscopy (SEM). Energy dispersive X-Ray (EDX) demonstrated the elemental analysis. Raman spectroscopy opens the gap between bonding structure of as-synthesized nanocomposite. From photoluminence (PL) spectra the energy band gap value 3.86 eV was estimated. Electrode properties were characterized by applying electrochemical observations such as cyclic voltammetry along with electrochemical impedance spectroscopy (EIS) for understanding redox mechanism and electron transfer rate constant K_app. Additionally, this novel work will be an assessment to analyze the capacitive behavior of electrode in different electrolytes such as in acidic of 0.1 M H₂SO₄ has specific capacitance C_sp = 525 F/g at 10 mVs⁻¹ and much low value in basic of 1 M KOH electrolyte. This paper reflects the novel synthesis and applications of MXene/Ag₂CrO₄ nanocomposite electrode fabrication in energy storage devices such as supercapacitors.