Comparison of the mechanical performance of three types of external fixators: linear, circular and hybrid

Different configurations of the Monticelli-Spinelli and Ilizarov external fixation systems were tested to define their mechanical properties. In five configurations the external fixator consisted of rings with tensioned wires (circular), while in one configuration two pairs of the tensioned wires and their correspondent ring were replaced by threaded pins (hybrid). Testing was performed in axial compression, bending and torsion. The results were compared to the characteristics of a selected linear fixator group. Both the circular and the hybrid configurations were non-linear in compression. In bending, circular fixators had a similar pattern in both anteroposterior and oblique loading directions. The bending load-displacement pattern for the hybrid fixators was similar to the linear fixators, higher stiffness in the plane of the pins. Torsion was linear for both circular and hybrid fixators, as for the linear fixators. By combination of wires and pins (hybrid configuration), the mechanical behaviour had characteristics from both linear and circular fixators. It is concluded that the three studied groups own different mechanical performance and can be considered as different types of fixators. While it has been demonstrated that osteogenesis can be achieved independently of the mechanical behaviour of the fixator, this study supports the suggestion that some complications can be related to the mechanical behaviour of the fixator.     

Stimulation of proinsulin biosynthesis by K+ in rat pancreatic islets

Glucose-stimulated proinsulin biosynthesis is regulated mainly at the translational level. This study aims at investigating the possible role of the B-cell K⁺ content in such a process. In order to increase the islet cells K⁺ content, rat pancreatic islets exposed to a low D-glucose concentration (e.g., 2.5 mM) were incubated in the presence of 30 or 60 mM K⁺, as distinct from a control extracellular K⁺ concentration of 5 mM. Under these conditions, the K⁺ content of the islets, as judged from the net uptake of ⁸⁶Rb⁺ over 60 min incubation, was increased to a level comparable to that otherwise found in the presence of 16.7 mM D-glucose. In the presence of 2.5–4.0 mM D-glucose, the rise in K⁺ concentration from 5 to 30 and 60 mM caused a progressive increase in the incorporation of l-[4-³H]phenylalanine into both all islet peptides and (pro)insulin. A preferential stimulation of proinsulin biosynthesis was only observed in islets incubated at 60 mM K⁺ in the presence of 4.0 mM D-glucose. In relative terms, the K⁺-induced increase in biosynthetic variables was less pronounced, however, than that otherwise evoked by a rise in D-glucose concentration from 2.5 to 4.0 mM to 5.6 or 16.7 mM. These findings may suggest that the effect of D-glucose to increase the K⁺ content of islet cells represents one modality for coupling a rise in D-glucose concentration to stimulation of proinsulin biosynthesis.     

Cholecystocholedocholithiasis: a case–control study comparing the short- and long-term outcomes for a “laparoscopy-first” attitude with the outcome for sequential treatment (systematic endoscopic sphincterotomy followed by laparoscopic cholecystectomy)

Background  

No unanimous consensus has been achieved regarding the ideal management of cholecystocholedocholithiasis. The treatment of gallbladder and common bile duct (CBD) stones may be achieved currently according to a two-step-protocol (endoscopic sphincterotomy associated with laparoscopic cholecystectomy) or by a one-step laparoscopic procedure, including exploration of the CBD and cholecystectomy. Endoscopic sphincterotomy is reported to have considerable morbidity/mortality and CBD stone recurrence rates, whereas laparoscopic CBD clearance is a demanding procedure, which to date has not spread beyond specialized environments.     

A short neuropsychologic and cognitive evaluation of frontotemporal dementia

Objective

To elaborate a brief but efficient neuropsychological assessment of frontotemporal dementia (FTD), selecting the most specific and sensitive cognitive and behavioural items for distinguish between AD and FTD in the earlier dementia stages.

Methods

Retrospective study with three groups, 35 patients with FTD, 46 with AD and 36 normal subjects, were administered the MMSE, FAB, Tower of London and Stoop's test along with a 98 items behavioural and cognitive questionnaire. The most sensitive items were selected and validated internally for diagnosis by lineal discriminant analysis.

Results

From the 98 items in the questionnaire, 29 showed significant discriminatory power. Non-cognitive symptoms with higher odd-ratio for FTD compared to AD were impairment in social behaviour (disinhibition, aggressiveness), loss of insight and inappropriate acts. Language disorders, such as echolalia, verbal apraxia or aggramatism, dominate in the cognitive profile of FTD. FAB was confirmed as the best cognitive instrument to differentiate FTD and AD. A linear discriminant function with the combination of the FAB score and the items from our questionnaire with higher OR for FTD accurately classified 97% of individuals.

Conclusions

The neuropsychological tests allow the differentiation between FTD and AD. The combination of FAB test with the assessment of key behavioural and cognitive symptoms appears helpful in this distinction.     

Phylogeny of human T cell lymphotropic virus type 1 in Peru: a high degree of evolutionary relatedness with South African isolates

We investigated the prevalence and molecular epidemiology of human T cell lymphotropic virus type 1 in Peruvian HIV-1-positive subjects, and found a 10.1% prevalence in a consecutive series of 318 HIV-1-positive patients living in Lima. Phylogenetic analysis of the long terminal repeat of 10 patient isolates showed that all of them belonged to the HTLV-1aA (Transcontinental) subgroup. Although the majority of the Peruvian sequences included in the analysis formed a clade with other Latin American sequences, the isolates of three patients clustered significantly with South African strains. These data show a high prevalence of HTLV-1 infection in HIV-1-positive subjects living in Lima and confirm the presence in Latin America of HTLV-1 strains probably arising from South Africa.     

Protein-tyrosine phosphatase 1B-deficient myocytes show increased insulin sensitivity and protection against tumor necrosis factor-alpha-induced insulin resistance

Protein-tyrosine phosphatase (PTP)1B is a negative regulator of insulin signaling and a therapeutic target for type 2 diabetes. In this study, we have assessed the role of PTP1B in the insulin sensitivity of skeletal muscle under physiological and insulin-resistant conditions. Immortalized myocytes have been generated from PTP1B-deficient and wild-type neonatal mice. PTP1B(-/-) myocytes showed enhanced insulin-dependent activation of insulin receptor autophosphorylation and downstream signaling (tyrosine phosphorylation of insulin receptor substrate [IRS]-1 and IRS-2, activation of phosphatidylinositol 3-kinase, and serine phosphorylation of AKT), compared with wild-type cells. Accordingly, PTP1B(-/-) myocytes displayed higher insulin-dependent stimulation of glucose uptake and GLUT4 translocation to the plasma membrane than wild-type cells. Treatment with tumor necrosis factor-alpha (TNF-alpha) induced insulin resistance on glucose uptake, impaired insulin signaling, and increased PTP1B activity in wild-type cells. Conversely, the lack of PTP1B confers protection against insulin resistance by TNF-alpha in myocyte cell lines and in adult male mice. Wild-type mice treated with TNF-alpha developed a pronounced hyperglycemia along the glucose tolerance test, accompanied by an impaired insulin signaling and increased PTP1B activity in muscle. However, mice lacking PTP1B maintained a rapid clearance of glucose and insulin sensitivity and displayed normal muscle insulin signaling regardless the presence of TNF-alpha.