A Combination of Constitutive Damage Model and Artificial Neural Networks to Characterize the Mechanical Properties of the Healthy and Atherosclerotic Human Coronary Arteries

It has been indicated that the content and structure of the elastin and collagen of the arterial wall can subject to a significant alteration due to the atherosclerosis. Consequently, a high tissue stiffness, stress, and even damage/rupture are triggered in the arterial wall. Although many studies so far have been conducted to quantify the mechanical properties of the coronary arteries, none of them consider the role of collagen damage of the healthy and atherosclerotic human coronary arterial walls. Recently, a fiber family‐based constitutive equation was proposed to capture the anisotropic mechanical response of the healthy and atherosclerotic human coronary arteries via both the histostructural and uniaxial data. In this study, experimental mechanical measurements along with histological data of the healthy and atherosclerotic arterial walls were employed to determine the constitutive damage parameters and remodeling of the collagen fibers. To do this, the preconditioned arterial tissues were excised from human cadavers within 5‐h postmortem, and the mean angle of their collagen fibers was precisely determined. Thereafter, a group of quasistatic axial and circumferential loadings were applied to the arterial walls, and the constrained nonlinear minimization method was employed to identify the arterial parameters according to the axial and circumferential extension data. The remodeling of the collagen fibers during the tensile test was also predicted via Artificial Neural Networks algorithm. Regardless of loading direction, the results presented a noteworthy load‐bearing capability and stiffness of the atherosclerotic arteries compared to the healthy ones (P < 0.005). Theoretical fiber angles were found to be consistent with the experimental histological data with less than 2 and 5° difference for the healthy and atherosclerotic arterial walls, respectively. The pseudoelastic damage model data were also compared with that of the experimental data, and interestingly, the arterial mechanical behavior for both the primary loading (up to the elastic region) and the discontinuous softening (up to the ultimate stress) was well addressed. The proposed model predicted well the mechanical response of the arterial tissue considering the damage of collagen fibers for both the healthy and atherosclerotic arterial walls.     

Post‐COVID‐19 maxillary osteonecrosis and floating maxillary teeth due to mucormycosis in two uncontrolled diabetic patients

Mucormycosis is a rare, invasive, quickly progressing fungal infection that generally affects patients who are immunocompromised. If left untreated, the disease is characterized by progressive necrosis and is often fatal. We present two cases of post‐COVID‐19 mucormycosis with a history of several years of uncontrolled diabetic mellitus.     

Study of programmed cell death 1 (PDCD1) gene polymorphims in Iranian patients with ankylosing spondylitis

Ankylosing spondylitis (AS) is a chronic inflammatory disease, characterized by axial arthritis in which the genetic-environmental factors seem to be involved in the pathogenesis of the disease. This study was performed to investigate the role of polymorphisms of the programmed cell death 1 (PDCD1) gene on susceptibility to AS. In this study, 161 Iranian patients with AS and 208 normal controls were enrolled; two single-nucleotide polymorphisms (SNPs) of the PDCD1 gene PD-1.3 (G, A) in nucleotide position +7146 of intron 4 and PD-1.9 (C, T) in nucleotide +7625 of exon 5 were studied. Analysis of PD-1.3 revealed that 82% of patients and 79% of controls had GG genotype, while GA and AA genotypes were detected in 17% and 0.6% of patients, respectively, and 20% and 1.4% of controls, respectively. Moreover, the genotype CC (PD-1.9) was present in 92% of patients and 97% of controls. Although these differences were not statistically significant between patients and controls, comparisons of genotypes frequencies in the AS patients, based on human leukocyte antigen (HLA)-B27, revealed that all patients who had CT genotype (PD-1.9) were HLA-B27 positive, whereas 30% of patients with CC genotype were HLA-B27 negative. There was no evidence of association for PDCD1 SNPs with AS in our study, but CT genotype (PD-1.9) seems to be associated with HLA-B27 positivity in the patients with AS.     

Pain sensitivity is normalized after a repeated bout of eccentric exercise

Purpose

The purpose of this study was to investigate the effect of repeated bouts of eccentric exercise on the nociceptive withdrawal reflex (NWR) threshold, a measure of sensitivity in the spinal nociceptive system.

Methods

Sixteen healthy students (age 25.7 ± 0.6 years, BMI 24.8 ± 1 kg m^?2) participated in this randomized, controlled, crossover study. Two identical bouts of high-intensity eccentric exercises were performed on the tibialis anterior muscle 7 days apart. Control sessions involving no exercise were performed 4 weeks apart the exercise sessions. Pressure pain thresholds (PPT) and the NWR threshold were recorded before, immediately after, and 1 day after both bouts of exercise.

Results

Pressure pain thresholds decreased significantly at two of the muscle belly sites on the day after initial bout compared with baseline. NWR threshold decreased by 25 ± 4 % immediately after initial bout and by 30 ± 5 % the next day (p < 0.05) as an indication of generalized pain hypersensitivity. On the contrary, no changes were found in both pain thresholds after second bout of eccentric exercise indicating that both localized and generalized pain sensitivity were normalized.

Conclusion

In conclusion, this study for the first time documented that an initial bout of unaccustomed high-intensity eccentric exercise, which results in muscle soreness can induce central sensitization. A repeated bout of exercise, however, facilitates inherent protective spinal mechanisms against the development of muscle soreness.     

Clinical significance of glutamic acid decarboxylase antibodies in patients with epilepsy

Purpose: Glutamic acid decarboxylase antibodies (GADAs) have been detected in patients with epilepsy, but the clinical determinants of epilepsy associated with GADA have not been defined. Methods: We analyzed GADA with a radioimmunoassay in sera of 253 well‐characterized patients with epilepsy and 200 control subjects. The positive samples were confirmed by immunohistochemistry and western blotting (WB). Sera were screened for other autoantibodies. Results: GADA were detected in 15 patients (5.9%) and in three control subjects (1.5%) (p = 0.026). Seven patients (2.8%) had high GADA titers [≥1,000 relative units (RUs)/ml], six of whom had temporal lobe epilepsy (TLE). All three GADA‐positive control subjects had low titers. Two of the five patients with high GADA titers and available cerebrospinal fluid (CSF) samples had intrathecal synthesis (IS) of GADA; one patient had CSF oligoclonal bands. The prevalence of increased levels of GADA tended to be higher in patients with TLE than in patients with extra‐TLE [odds ratio (OR) 1.32, 95% confidence interval (CI) 0.39–4.42; p = 0.657]. The patients with high GADA titers had significantly higher number of other autoantibodies compared to the patients with low GADA titers (p = 0.001) and the patients with normal GADA (p < 0.001). Discussion: High GADA titers were present in a subgroup of patients; close to 90% had TLE. The immunologic profile of these patients suggests that the most probable origin of their epilepsy is autoimmune. A positive IS of GADA may be a marker of an ongoing immune response that could identify those patients in whom a trial with immunosuppressive therapy might be warranted.     

A comparison of 8 and 16 frames gated SPECT imaging for determination of left ventricular volumes and ejection fraction: effects of gender and myocardial counts

The International Journal of Cardiovascular Imaging - In myocardial gated SPECT imaging each cardiac cycle is divided into 8 or 16 temporal frames and the cause of the difference between 8 and 16...