Intracrystalline proteins and urolithiasis: a synchrotron X-ray diffraction study of calcium oxalate monohydrate.

The existence of intracrystalline proteins and amino acids in calcium oxalate monohydrate was demonstrated by X-ray synchrotron diffraction studies. Their presence has implications for the destruction of calcium oxalate crystals formed in the urinary tract and the prevention of kidney stones. INTRODUCTION: Although proteins are present in human kidney stones, their role in stone pathogenesis remains unknown. This investigation aimed to characterize the nature of the relationship between the organic and mineral phases in calcium oxalate monohydrate (COM) crystals grown in human urine and in aqueous solutions of proteins and amino acids to clarify the function of proteins in urolithiasis. METHODS: COM crystals were grown in human urine and in aqueous solutions containing either human prothrombin (PT), Tamm-Horsfall glycoprotein (THG), aspartic acid (Asp), aspartic acid dimer (AspAsp), glutamic acid (Glu), glutamic acid dimer (GluGlu), or gamma-carboxyglutamic acid (Gla). Controls consisted of COM crystals precipitated from pure inorganic solutions or from human urine that had been ultrafiltered to remove macromolecules. Synchrotron X-ray diffraction with Rietveld whole-pattern peak fitting and profile analysis was used to determine nonuniform crystal strain and crystallite size in polycrystalline samples. RESULTS: Crystals precipitated from ultrafiltered urine had lower nonuniform strain than those grown in urine or in aqueous PT solution. Nonuniform strain was much lower in crystals grown in distilled water or in the presence of THG. For the amino acids, the highest nonuniform strain was exhibited by crystals grown in Gla solution, followed by Glu. Crystallite size was inversely related to nonuniform strain, with the effect being significantly less for amino acids than for macromolecules. CONCLUSIONS: Selected proteins and amino acids associated with COM crystals are intracrystalline. Although their incorporation into the mineral bulk would be expected to affect the rate of crystal growth, they also have the potential to influence the phagocytosis and intracellular destruction of any crystals nucleated and trapped within the renal collecting system. Crystals impregnated with protein would be more susceptible to digestion by cellular proteases, which would provide access to the crystal core, thereby facilitating further proteolytic degradation and mineral dissolution. We therefore propose that intracrystalline proteins may constitute a natural form of defense against renal stone formation.     

Endogenous norepinephrine regulates blood flow to the intact rat tibia.

The goal of our study was to determine if endogenous norepinephrine (NE) has a role in the regulation of basal blood flow to intact bone. The experimental plan was to measure bone blood flow before and after pharmacological blockade of alpha-adrenergic receptors. A significant increase in blood flow after receptor blockade would suggest that endogenous norepinephrine exerts a tonic constrictor effect on the vessels supplying blood to the bone. Mature, male rats were anesthetized with Inactin. Arterial blood pressure and left tibia blood flow (laser Doppler flowmetry) were measured. A cannula was inserted into the right iliac artery and advanced to the aortic bifurcation to deliver drugs into the left hindlimb circulation, including the left tibia vasculature. Bolus injection of norepinephrine caused a dose-dependent decrease in bone blood flow (30-40%). Blockade of alpha-adrenergic receptors with phentolamine or phenoxybenzamine attenuated by more than 50% the norepinephrine-induced decrease in bone blood flow. In separate rats that had not received exogenous norepinephrine, injection of phentolamine alone decreased bone vascular resistance by 34+/-3%. Similarly, phenoxybenzamine decreased resistance by 25+/-4%. These results are consistent with the conclusion that alpha-adrenergic receptors mediate a significant constriction of blood vessels which participate in the partial control of basal blood flow to the intact rat tibia.     

Self-awareness of prospective memory failure in adults with traumatic brain injury

The frequency of prospective memory failure in individuals with severe traumatic brain injury (TBI) was investigated by comparison with a non-brain-injured control group. Self-awareness of prospective memory function was also assessed by comparing self-ratings with ratings by significant others. Study participants included 33 individuals with severe TBI and 29 non-brain-injured persons. Each participant nominated a close friend or relative who completed the informant's version of the questionnaire. Participants and their significant others both rated the participants' frequency of prospective memory lapses using the Comprehensive Assessment of Prospective Memory (CAPM). An independent groups design was adopted to compare the TBI and control groups. No significant difference was found between the TBI and control participants' self-ratings of frequency of prospective memory failure, but ratings by significant others were significantly different. The TBI group demonstrated less self-awareness (i.e. underestimated the frequency of prospective memory failure compared to significant others) than the control group.     

Cardiac function during laparoscopic vs open gastric bypass

BACKGROUND: Hypercarbia and increased intraabdominal pressure during prolonged pneumoperitoneum can adversely affect cardiac function. This study compared the intraoperative hemodynamics of morbidly obese patients during laparoscopic and open gastric bypass (GBP). METHODS: Fifty-one patients with a body mass index (BMI) of 40-60 kg/m2 were randomly allocated to undergo laparoscopic (n = 25) or open (n = 26) GBP. Cardiac output (CO), mean pulmonary artery pressure (MPAP), pulmonary artery wedge pressure (PAWP), central venous pressure (CVP), heart rate (HR), and mean arterial pressure (MAP) were recorded at baseline, intraoperatively at 30-min intervals, and in the recovery room. Systemic vascular resistance (SVR) and stroke volume (SV) were also calculated. RESULTS: The two groups were similar in terms of age, weight, and BMI. Operative time was longer in the laparoscopic than in the open group (p < 0.05). The HR and MAP increased significantly from baseline intraoperatively, but there was no significant difference between the two groups. In the laparoscopic group, CO was unchanged after insufflation, but it increased by 5.3% at 2.5 h compared to baseline and by 43% compared to baseline in the recovery room. In contrast, during open GBP, CO increased significantly by 25% after surgical incision and remained elevated throughout the operation. CO was higher during open GBP than during laparoscopic GBP at 0.5 h and at 1 h after surgical incision (p < 0.05). During laparoscopic GBP, CVP, MPAP, and SVR increased transiently and PAWP remained unchanged. During open GBP, CVP, MPAP, and PAWP decreased transiently and SVR remained unchanged. There was no significant difference in the amount of intraoperative fluid administered during laparoscopic (5.5 +/- 1.6 L) and open (5.6 +/- 1.7 L) GBP. CONCLUSION: Prolonged pneumoperitoneum during laparoscopic gastric bypass does not impair cardiac function and is well tolerated by morbidly obese patients.     

The effect of hepatic inflow occlusion on laparoscopic radiofrequency ablation using simulated tumors

BACKGROUND: The purpose of this study was to determine the effect of hepatic inflow occlusion (the Pringle maneuver) on laparoscopic radiofrequency (RF) ablation. METHODS: Using a previously validated agarose tissue-mimic model, 1-cm simulated hepatic tumors (three per animal) were laparoscopically ablated in five pigs with normal perfusion and then in five pigs with hepatic artery and portal vein occlusion. Energy was applied until tissue temperature reached 100 degrees C (warm-up) and thereafter for eight min. Specimens were examined immediately after treatment. RESULTS: Vascular occlusion was successful in all cases per color-flow Doppler ultrasound. Pringle time was 11.4 +/- 1.6 min. Warm-up time (2.7 +/- 1.4 vs 20.2 +/- 14.0 min) was significantly faster in the Pringle group. Ablation diameter (34.8 +/- 2.9 vs 24.7 +/- 3.1 mm), proportion of round/ovoid lesions (93% vs 20%), ablation symmetry (100% vs 40%), and margin distance (5.1 +/- 3.0 vs 1.1 +/- 1.2 mm) were significantly better for the Pringle group than the No Pringle group, respectively. CONCLUSION: Using a Pringle maneuver during laparoscopic RF ablation significantly enhances ablation geometry and results in larger margins.     

Comparison of video trainer and virtual reality training systems on acquisition of laparoscopic skills

Training on a video trainer or computer-based minimally invasive surgery trainer leads to improved benchtop laparoscopic skill. Recently, improved operative performance from practice on a video trainer was reported. The purpose of this study was three fold: (a) to compare psychomotor skill improvement after training on a virtual reality (VR) system with that after training on a video-trainer, (VT) (b) to evaluate whether skills learned on the one training system are transferable to the other, and (c) to evaluate whether VR or VT training improves operative performance. For the study, 50 junior surgery residents completed baseline skill testing on both the VR and VT systems. These subjects then were randomized to either a VR or VT structured training group. After practice, the subjects were tested again on their VR and VT skills. To assess the effect of practice on operative performance, all second-year residents (n = 19) were evaluated on their operative performance during a laparoscopic cholecystectomy before and after skill training. Data are expressed as percentage of improvement in mean score/time. Analysis was performed by Student's paired t-test. The VR training group showed improvement of 54% on the VR posttest, as compared with 55% improvement by the VT group. The VR training group improved more on the VT posttest tasks (36%) than the VT training group improved on the VR posttest tasks (17%) (p <0.05). Operative performance improved only in the VR training group (p <0.05). Psychomotor skills improve after training on both VR and VT, and skills may be transferable. Furthermore, training on a minimally invasive surgery trainer, virtual reality system may improve operative performance during laparoscopic cholecystectomy.     

Electron beam sterilization does not have a detrimental effect on the ability of extracellular matrix scaffolds to support in vivo ligament healing

Extracellular matrix (ECM) scaffolds have been used to enhance anterior cruciate ligament (ACL) repair in large animal models. To translate this technology to clinical care, identifying a method which effectively sterilizes the material without significantly impairing in vivo function is desirable. Sixteen Yorkshire pigs underwent ACL transection and were randomly assigned to bridge‐enhanced ACL repair—primary suture repair of the ACL with addition of autologous blood soaked ECM scaffold—with either (i) an aseptically processed ECM scaffold, or (ii) an electron beam irradiated ECM scaffold. Primary outcome measures included sterility of the scaffold and biomechanical properties of the scaffold itself and the repaired ligament at 8 weeks after surgery. Scaffolds treated with 15 kGy electron beam irradiation had no bacterial or fungal growth noted, while aseptically processed scaffolds had bacterial growth in all tested samples. The mean biomechanical properties of the scaffold and healing ligament were lower in the electron beam group; however, differences were not statistically significant. Electron beam irradiation was able to effectively sterilize the scaffolds. In addition, this technique had only a minimal impact on the in vivo function of the scaffolds when used for ligament healing in the porcine model. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:1015–1023, 2015.     

A new device to measure knee laxity during weightbearing and non-weightbearing conditions.

The Vermont knee laxity device (VKLD) was developed to evaluate anterior-posterior (A-P) displacement of the tibia relative to the femur (A-P laxity) during weightbearing and non-weightbearing conditions. The purposes of this study were to determine the repeatability and reliability of the VKLD measurements of A-P laxity and to compare them with two devices currently in clinical use: the KT-1000 knee arthrometer and planar stress radiography. Two independent examiners tested six subjects with no history of knee injury. A-P laxity was measured on three separate days with the KT-1000 and the VKLD. With the VKLD, A-P laxity was measured in the weightbearing and non-weightbearing conditions. In addition, one examiner measured A P laxity in each subject on each day using a planar stress radiography technique. Similar A-P laxity values were obtained with the KT-1000 and the VKLD; however, the planar stress radiography technique measured less A-P laxity compared to the VKLD (9.2+/-2.2 mm versus 13.3+/-2.9 mm, P = 0.0004). None of the three devices showed significant differences in measuring A-P laxity between days. During weightbearing, A-P laxity was reduced by 65-70% compared to the non-weightbearing condition (P = 0.0001). Future investigations will use the VKLD to study subjects that have suffered injury to the anterior and posterior cruciate ligaments.     

Social Media and Organ Donor Registration: The Facebook Effect

Despite countless media campaigns, organ donation rates in the United States have remained static while need has risen dramatically. New efforts to increase organ donation through public education are necessary to address the waiting list of over 100,000 patients. On May 1, 2012, the online social network, Facebook, altered its platform to allow members to specify “Organ Donor” as part of their profile. Upon such choice, members were offered a link to their state registry to complete an official designation, and their “friends” in the network were made aware of the new status as a donor. Educational links regarding donation were offered to those considering the new organ donor status. On the first day of the Facebook organ donor initiative, there were 13 054 new online registrations, representing a 21.1‐fold increase over the baseline average of 616 registrations. This first‐day effect ranged from 6.9× (Michigan) to 108.9× (Georgia). Registration rates remained elevated in the following 12 days. During the same time period, no increase was seen in registrations from the DMV. Novel applications of social media may prove effective in increasing organ donation rates and likewise might be utilized in other refractory public health problems in which communication and education are essential.