Investigation of the mechanical properties of the human crural fascia and their possible clinical implications

The mechanical properties of deep fasciae strongly affect muscular actions, development of pathologies, such as acute and chronic compartment syndromes, and the choice of the various fascial flaps. Actually, a clear knowledge of the mechanical characterization of these tissues still lacks. This study focuses attention on experimental tests of different regions of human crural fascia taken from an adult frozen donor. Tensile tests along proximal–distal and medial–lateral direction at a strain rate of 120 %/s were performed at the purpose of evaluating elastic properties. Viscous phenomena were investigated by applying incremental relaxation tests at total strain of 7, 9 and 11 % and observing stress decay for a time interval of 240 s. The elastic response showed that the fascia in the anterior compartment is stiffer than in the posterior compartment, both along the proximal–distal and medial–lateral directions. This result can explain why the compartment syndromes are more frequent in this compartment with respect to posterior one. Furthermore, the fascia is stiffer along the proximal–distal than along medial–lateral direction. This means that the crural fascia can adapt to the muscular variation of volume in a transversal direction, while along the main axis it could be considered as a structure that contributes to transmitting the muscular forces at a distance and connecting the different segments of the limb. The stress relaxation tests showed that the crural fascia needs 120 s to decrease stress of 40 %, suggesting a similar time also in the living so that the static stretching could have an effect on the fascia.     

Temporal Kinetics and Quantitative Analysis of Cryptococcus neoformans Nonlytic Exocytosis

Cryptococcus neoformans is a facultative intracellular pathogen and the causative agent of cryptococcosis, a disease that is often fatal to those with compromised immune systems. C. neoformans has the capacity to escape phagocytic cells through a process known as nonlytic exocytosis whereby the cryptococcal cell is released from the macrophage into the extracellular environment, leaving both the host and pathogen alive. Little is known about the mechanism behind nonlytic exocytosis, but there is evidence that both the fungal and host cells contribute to the process. In this study, we used time-lapse movies of C. neoformans-infected macrophages to delineate the kinetics and quantitative aspects of nonlytic exocytosis. We analyzed approximately 800 macrophages containing intracellular C. neoformans and identified 163 nonlytic exocytosis events that were further characterized into three subcategories: type I (complete emptying of macrophage), type II (partial emptying of macrophage), and type III (cell-to-cell transfer). The majority of type I and II events occurred after several hours of intracellular residence, whereas type III events occurred significantly (P < 0.001) earlier in the course of macrophage infection. Our results show that nonlytic exocytosis is a morphologically and temporally diverse process that occurs relatively rapidly in the course of macrophage infection.     

Experimental model standardizing polyvinyl alcohol hydrogel to simulate endoscopic ultrasound and endoscopic ultrasound-elastography

BACKGROUND Endoscopic ultrasound(EUS) and endoscopic ultrasound elastography(EUS-E) simulation lessens the learning curve; however, models lack realism, diminishing competitiveness.AIM To standardize the mechanical properties of polyvinyl alcohol(PVA) hydrogel for simulating organs and digestive lesions.METHODS PVA hydrogel(Sigma Aldrich, degree of hydrolysis 99%) for simulating EUS/EUS-E lesions was investigated in Unidad de Investigación y Desarrollo Tecnológico at Hospital General de México "Dr. Eduardo Liceaga", Mexico City. We evaluated physical, contrast, elasticity and deformation coefficient characteristics in lesions, applying Kappa's concordance and satisfaction questionnaire(Likert 4-points).RESULTS PVA hydrogel showed stable mechanical properties. Density depended on molecular weight(MW) and concentration(C). PVA bblocks with the greatest density showed lowest tensile strength(r =-0.8, P = 0.01). Lesions were EUSgraphically visible. Homogeneous and heterogeneous examples were created from PVA blocks or PVA phantoms, exceeding(MW_2 = 146000-186000, C_9 = 15% and C_(10) = 20%) with a density under(MW_1 = 85000-124000, C_1 = 7% and C_2 = 9%). We calculated elasticity and deformation parameters of solid(blue) areas, contrasting with the norm(Kappa = 0.8; high degree of satisfaction).CONCLUSION PVA hydrogels were appropriate for simulating organs and digestive lesions using EUS/EUS-E, facilitating practice and reducing risk. Repetition amplified skills, while reducing the learning curve.     

Mechanisms for the antihyperglycemic effect of sitagliptin in patients with type 2 diabetes

Context: Dipeptidyl peptidase IV (DPP-4) inhibitors improve glycemic control in patients with type 2 diabetes. The underlying mechanisms (incretin effect, β-cell function, endogenous glucose production) are not well known. Objective: The aim of the study was to examine mechanisms of the antihyperglycemic effect of DPP-4 inhibitors. Design, Setting, and Patients: We administered a mixed meal with glucose tracers ([6,6-(2)H(2)]-glucose infused, [1-(2)H]-glucose ingested), and on a separate day, a glucose infusion matched the glucose responses to the meal (isoglycemic test) in 50 type 2 diabetes patients (hemoglobin A(1c) = 7.4 ± 0.8%) and seven controls; 47 diabetic completers were restudied after 6 wk. Glucose fluxes were calculated, and β-cell function was assessed by mathematical modeling. The incretin effect was calculated as the ratio of oral to iv insulin secretion. Intervention: We conducted a 6-wk, double-blind, randomized treatment with sitagliptin (100 mg/d; n = 25) or placebo (n = 22). Results: Relative to placebo, meal-induced changes in fasting glucose and glucose area under the curve (AUC) were greater with sitagliptin, in parallel with a lower appearance of oral glucose [difference (post-pre) AUC = -353 ± 915 vs. +146 ± 601 μmol · kg(-1) · 5 h] and greater suppression of endogenous glucose production. Insulin sensitivity improved 10%, whereas total insulin secretion was unchanged. During the meal, β-cell glucose sensitivity improved (+19[29] vs. 5[21] pmol · min(-1) · m(-2) · mm(-1); median [interquartile range]) and glucagon AUC decreased (19.6 ± 7.5 to 17.3 ± 7.1 ng · ml(-1) · 5 h), whereas intact glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1 AUC increased with sitagliptin vs. placebo. The incretin effect was unchanged because sitagliptin increased β-cell glucose sensitivity also during the isoglycemic test. Conclusions: Chronic sitagliptin treatment improves glycemic control by lowering the appearance of oral glucose, postprandial endogenous glucose release, and glucagon response, and by improving insulin sensitivity and β-cell glucose sensing in response to both oral and iv glucose.     

Child maltreatment: variation in trends and policies in six developed countries

We explored trends in six developed countries in three types of indicators of child maltreatment for children younger than 11 years, since the inception of modern child protection systems in the 1970s. Despite several policy initiatives for child protection, we recorded no consistent evidence for a decrease in all types of indicators of child maltreatment. We noted falling rates of violent death in a few age and country groups, but these decreases coincided with reductions in admissions to hospital for maltreatment-related injury only in Sweden and Manitoba (Canada). One or more child protection agency indicators increased in five of six countries, particularly in infants, possibly as a result of early intervention policies. Comparisons of mean rates between countries showed five-fold to ten-fold differences in rates of agency indicators, but less than two-fold variation in violent deaths or maltreatment-related injury, apart from high rates of violent child death in the USA. These analyses draw attention to the need for robust research to establish whether the high and rising rates of agency contacts and out-of-home care in some settings are effectively reducing child maltreatment.     

Mapping of alpha-neo-endorphin- and neurokinin B-immunoreactivity in the human brainstem

We have studied the distribution of alpha-neo-endorphin- or neurokinin B-immunoreactive fibres and cell bodies in the adult human brainstem with no prior history of neurological or psychiatric disease. A low density of alpha-neo-endorphin-immunoreactive cell bodies was only observed in the medullary central gray matter and in the spinal trigeminal nucleus (gelatinosa part). Alpha-neo-endorphin-immunoreactive fibres were moderately distributed throughout the human brainstem. A high density of alpha-neo-endorphin-immunoreactive fibres was found only in the solitary nucleus (caudal part), in the spinal trigeminal nucleus (caudal part), and in the gelatinosa part of the latter nucleus. Neurokinin B-immunoreactive cell bodies (low density) were found in the periventricular central gray matter, the reticular formation of the pons and in the superior colliculus. The distribution of the neurokinin-immunoreactive fibres was restricted. In general, for both neuropeptides the density of the immunoreactive fibres was low. In the human brainstem, the proenkephalin system was more widely distributed than the prodynorphin system, and the preprotachykinin A system (neurokinin A) was more widely distributed than the preprotachykinin B system (neurokinin B).     

Development of an animal model to investigate optimal laparoscopic trocar site fascial closure

Background

The rate of hernia formation after closure of 10–12 mm laparoscopic trocar sites is grossly under-reported. Using an animal model, we have developed a method to assess trocar site fascial dehiscence and the strength of different methods of fascial closure.

Materials and methods

Pigs (n = 9; 17 ± 2.5 lbs) underwent placement of 12 mm Hasson trocars with pneumoperitoneum maintained for 1 h. Three closure techniques (Figure-of-eight; simple interrupted; pulley) were compared with no fascial closure and to native fascia at five randomly allocated abdominal wall midline locations. Necropsy was performed on the fourth postoperative d. Statistical comparisons of tensile strength and breaking strength based on closure type and trocar location were made using ANOVA with Tukey’s tests.

Results

The mean (SD) force (Newtons) required for fascial disruption varied significantly with closure type [Native Fascia 170 (39), Figure-of-eight 169 (31), Pulley 167 (59), Simple Interrupted 151 (27), No Closure 108 (28)]; P = 0.007. The mean force required for fascial disruption was significantly increased for Native Fascia, Figure-of-eight, and Pulley relative to No Closure (P = 0.013, P = 0.015, P = 0.023, respectively). The mean (SD) force (in Newtons) required for fascial disruption also varied significantly with location of trocar [subxiphoid 181 (43), supraumbilical 151 (23), Umbilical 146 (23), infraumbilical 168 (62), suprapubic 120 (38)]; P = 0.03. The mean force for subxiphoid location was significantly increased relative to the suprapubic location (P = 0.021).

Conclusions

We have developed a novel assessment model that reliably detects differences in fascial integrity after laparoscopic trocar placement and closure. This model will allow for further testing of various trocars and closure techniques, and facilitate hernia prevention strategies.