Regular and platform switching: bone stress analysis varying implant type

Purpose: This study aimed to evaluate stress distribution on peri‐implant bone simulating the influence of platform switching in external and internal hexagon implants using three‐dimensional finite element analysis. Materials and Methods: Four mathematical models of a central incisor supported by an implant were created: External Regular model (ER) with 5.0 mm × 11.5 mm external hexagon implant and 5.0 mm abutment (0% abutment shifting), Internal Regular model (IR) with 4.5 mm × 11.5 mm internal hexagon implant and 4.5 mm abutment (0% abutment shifting), External Switching model (ES) with 5.0 mm × 11.5 mm external hexagon implant and 4.1 mm abutment (18% abutment shifting), and Internal Switching model (IS) with 4.5 mm × 11.5 mm internal hexagon implant and 3.8 mm abutment (15% abutment shifting). The models were created by SolidWorks software. The numerical analysis was performed using ANSYS Workbench. Oblique forces (100 N) were applied to the palatal surface of the central incisor. The maximum (σ_max) and minimum (σ_min) principal stress, equivalent von Mises stress (σ_vM), and maximum principal elastic strain (ε_max) values were evaluated for the cortical and trabecular bone. Results: For cortical bone, the highest stress values (σ_max and σ_vm) (MPa) were observed in IR (87.4 and 82.3), followed by IS (83.3 and 72.4), ER (82 and 65.1), and ES (56.7 and 51.6). For ε_max, IR showed the highest stress (5.46e‐003), followed by IS (5.23e‐003), ER (5.22e‐003), and ES (3.67e‐003). For the trabecular bone, the highest stress values (σ_max) (MPa) were observed in ER (12.5), followed by IS (12), ES (11.9), and IR (4.95). For σ_vM, the highest stress values (MPa) were observed in IS (9.65), followed by ER (9.3), ES (8.61), and IR (5.62). For ε_max, ER showed the highest stress (5.5e‐003), followed by ES (5.43e‐003), IS (3.75e‐003), and IR (3.15e‐003). Conclusion: The influence of platform switching was more evident for cortical bone than for trabecular bone, mainly for the external hexagon implants. In addition, the external hexagon implants showed less stress concentration in the regular and switching platforms in comparison to the internal hexagon implants.     

Syntaxin-11, but not syntaxin-2 or syntaxin-4, is required for platelet secretion

The platelet release reaction plays a critical role in thrombosis and contributes to the events that follow hemostasis. Previous studies have shown that platelet secretion is mediated by Soluble NSF Attachment Protein Receptor (SNARE) proteins from granule and plasma membranes. The SNAREs form transmembrane complexes that mediate membrane fusion and granule cargo release. Although VAMP-8 (v-SNARE) and SNAP-23 (a t-SNARE class) are important for platelet secretion, the identity of the functional syntaxin (another t-SNARE class) has been controversial. Previous studies using anti-syntaxin Abs in permeabilized platelets have suggested roles for both syntaxin-2 and syntaxin-4. In the present study, we tested these conclusions using platelets from syntaxin-knockout mouse strains and from a Familial Hemophagocytic Lymphohistiocytosis type 4 (FHL4) patient. Platelets from syntaxin-2 and syntaxin-4 single- or double-knockout mice had no secretion defect. Platelets from a FHL4 patient deficient in syntaxin-11 had a robust defect in agonist-induced secretion although their morphology, activation, and cargo levels appeared normal. Semiquantitative Western blotting showed that syntaxin-11 is the more abundant syntaxin in both human and murine platelets. Coimmunoprecipitation experiments showed that syntaxin-11 can form SNARE complexes with both VAMP-8 and SNAP-23. The results of the present study indicate that syntaxin-11, but not syntaxin-2 or syntaxin-4, is required for platelet exocytosis.     

Recollections of Parental Rejection,Self-Criticism and Depression in Suicidality

The present study examines whether self-criticism and depressive symptoms mediate the relationship between recollections of parental rejection and suicidality. A community sample of 200 Portuguese adults completed, in counterbalanced order, a socio-demographic questionnaire, the short form of the Inventory for Assessing Memories of Parental Rearing Behaviour (EMBU), the Depressive Experiences Questionnaire (DEQ), the Center for Epidemiologic Studies Depression Scale (CES-D), and reports of any suicide intention and/or ideation and suicide attempts. Structural Equation Modeling (SEM) indicated that recollections of parental rejection are significantly associated with depressive symptoms and suicidality. Recollections of parental rejection are indirectly associated with depressive symptoms and suicidality through self-criticism. The association between self-criticism and suicidality is mediated by depressive symptoms. In addition to a significant direct association between recollections of parental rejection and suicidality, the final model indicated that recollections of parental rejection are significantly associated with self-criticism. That same self-criticism is significantly associated with depressive symptoms which, in turn, are significantly associated with suicidality. Individuals with recollections of parental rejection are at greater risk for suicide ideation and behavior, possibly because such experiences predispose them to intense self-criticism which is a risk factor for depression associated with suicidal ideation and behavior.     

Haplotypes of the IL10 Gene as Potential Protection Factors in Leprosy Patients

Leprosy is an infectious disease caused by Mycobacterium leprae characterized by dermatoneurological signs and symptoms that has a large number of new cases worldwide. Several studies have associated interleukin 10 with susceptibility/resistance to several diseases. We investigated haplotypes formed by three single nucleotide polymorphisms (SNPs) located in the IL10 gene (A-1082G, C-819T, and C-592A) in order to better understand the susceptibility to and severity of leprosy in an admixed northern Brazil population, taking into account estimates of interethnic admixture. We observed the genotypes ACC/ACC (P = 0.021, odds ratio [OR] [95% confidence interval (CI)] = 0.290 [0.085 to 0823]) and ACC/GCC (P = 0.003, OR [95% CI] = 0.220 [0.504 to 0.040]) presenting significant results for protection against leprosy development, framed in the profiles of low and medium interleukin production, respectively. Therefore, we suggest that genotypes A-1082G, C-819T, and C-592A formed by interleukin-10 polymorphisms are closely related to protection of the leprosy development in an admixed northern Brazil population, in particular ACC/ACC and ACC/GCC genotypes.     

Resistin expression correlates with steatohepatitis in morbidly obese patients

Background

Morbidly obese patients are at risk for nonalcoholic steatohepatitis (NASH) even in the absence of risk factors for liver disease. Unfortunately, NASH is usually not clinically evident, and a definitive, noninvasive test for NASH does not exist. Resistin, a cytokine originating from adipose tissue, is involved in insulin resistance and also initiates proinflammatory signaling from hepatic stellate cells. This study explores the relationship between resistin expression and liver pathology in bariatric surgery patients.

Methods

Blood samples from 30 patients undergoing bariatric surgery were collected. Total RNA was extracted and cDNA was synthesized. Quantitative RT-PCR was used to quantify relative gene expression using 18s rRNA gene as an internal control. Wedge liver biopsies from these patients were sectioned and stained. Based on a previously published scoring method, biopsies were assigned an overall NASH severity score and subscores for steatosis, inflammation, and fibrosis. Results were analyzed by using Student’s t test.

Results

Resistin mRNA levels ranged from 0.5 to 9.7. A group of five patients with very high resistin expression (>4) was identified. These patients had a significantly higher average NASH score compared with the rest of the group (7.9 vs. 4.48, p = 0.019). Steatosis and inflammation scores were significantly higher in the high-resistin group (p < 0.05 for both comparisons). There also was a trend toward higher fibrosis score in this group, which approached statistical significance (p = 0.051).

Conclusions

In morbidly obese patients, high resistin expression in serum is associated with hepatic steatosis, inflammation, and fibrosis. The development of elevated resistin expression may represent a link between obesity and the onset of steatohepatitis.