Liver-specific knockout of arginase-1 leads to a profound phenotype similar to inducible whole body arginase-1 deficiency

Arginase-1 (Arg1) converts arginine to urea and ornithine in the distal step of the urea cycle in liver. We previously generated a tamoxifen-inducible Arg1 deficient mouse model (Arg1-Cre) that disrupts Arg1 expression throughout the whole body and leads to lethality ≈ 2 weeks after gene disruption. Here, we evaluate if liver-selective Arg1 loss is sufficient to recapitulate the phenotype observed in global Arg1 knockout mice, as well as to gauge the effectiveness of gene delivery or hepatocyte transplantation to rescue the phenotype. Liver-selective Arg1 deletion was induced by using an adeno-associated viral (AAV)-thyroxine binding globulin (TBG) promoter-Cre recombinase vector administered to Arg1 "floxed" mice; Arg1(fl/fl) ). An AAV vector expressing an Arg1-enhanced green fluorescent protein (Arg1-eGFP) transgene was used for gene delivery, while intrasplenic injection of wild-type (WT) C57BL/6 hepatocytes after partial hepatectomy was used for cell delivery to "rescue" tamoxifen-treated Arg1-Cre mice. The results indicate that liver-selective loss of Arg1 (> 90% deficient) leads to a phenotype resembling the whole body knockout of Arg1 with lethality ≈ 3 weeks after Cre-induced gene disruption. Delivery of Arg1-eGFP AAV rescues more than half of Arg1 global knockout male mice (survival > 4 months) but a significant proportion still succumb to the enzyme deficiency even though liver expression and enzyme activity of the fusion protein reach levels observed in WT animals. Significant Arg1 enzyme activity from engrafted WT hepatocytes into knockout livers can be achieved but not sufficient for rescuing the lethal phenotype. This raises a conundrum relating to liver-specific expression of Arg1. On the one hand, loss of expression in this organ appears to be both necessary and sufficient to explain the lethal phenotype of the genetic disorder in mice. On the other hand, gene and cell-directed therapies suggest that rescue of extra-hepatic Arg1 expression may also be necessary for disease correction. Further studies are needed in order to illuminate the detailed mechanisms for pathogenesis of Arg1-deficiency

From Dynamic Expression Patterns to Boundary Formation in the Presomitic Mesoderm

The segmentation of the vertebrate body is laid down during early embryogenesis. The formation of signaling gradients, the periodic expression of genes of the Notch-, Fgf- and Wnt-pathways and their interplay in the unsegmented presomitic mesoderm (PSM) precedes the rhythmic budding of nascent somites at its anterior end, which later develops into epithelialized structures, the somites. Although many in silico models describing partial aspects of somitogenesis already exist, simulations of a complete causal chain from gene expression in the growth zone via the interaction of multiple cells to segmentation are rare. Here, we present an enhanced gene regulatory network (GRN) for mice in a simulation program that models the growing PSM by many virtual cells and integrates WNT3A and FGF8 gradient formation, periodic gene expression and Delta/Notch signaling. Assuming Hes7 as core of the somitogenesis clock and LFNG as modulator, we postulate a negative feedback of HES7 on Dll1 leading to an oscillating Dll1 expression as seen in vivo. Furthermore, we are able to simulate the experimentally observed wave of activated NOTCH (NICD) as a result of the interactions in the GRN. We esteem our model as robust for a wide range of parameter values with the Hes7 mRNA and protein decays exerting a strong influence on the core oscillator. Moreover, our model predicts interference between Hes1 and HES7 oscillators when their intrinsic frequencies differ. In conclusion, we have built a comprehensive model of somitogenesis with HES7 as core oscillator that is able to reproduce many experimentally observed data in mice

Unified treatment algorithm for the management of crotaline snakebite in the United States: results of an evidence-informed consensus workshop

<p>Abstract</p> <p>Background</p> <p>Envenomation by crotaline snakes (rattlesnake, cottonmouth, copperhead) is a complex, potentially lethal condition affecting thousands of people in the United States each year. Treatment of crotaline envenomation is not standardized, and significant variation in practice exists.</p> <p>Methods</p> <p>A geographically diverse panel of experts was convened for the purpose of deriving an evidence-informed unified treatment algorithm. Research staff analyzed the extant medical literature and performed targeted analyses of existing databases to inform specific clinical decisions. A trained external facilitator used modified Delphi and structured consensus methodology to achieve consensus on the final treatment algorithm.</p> <p>Results</p> <p>A unified treatment algorithm was produced and endorsed by all nine expert panel members. This algorithm provides guidance about clinical and laboratory observations, indications for and dosing of antivenom, adjunctive therapies, post-stabilization care, and management of complications from envenomation and therapy.</p> <p>Conclusions</p> <p>Clinical manifestations and ideal treatment of crotaline snakebite differ greatly, and can result in severe complications. Using a modified Delphi method, we provide evidence-informed treatment guidelines in an attempt to reduce variation in care and possibly improve clinical outcomes.</p

Liver Biopsies for Chronic Hepatitis C: Should Nonultrasound-Guided Biopsies Be Abandoned?

BACKGROUND/OBJECTIVE: Liver biopsy has been the gold standard for grading and staging chronic hepatitis C virus (HCV)-mediated liver injury. Traditionally, this has been performed by trained practitioners using a nonimage-guided percutaneous technique at the bedside. Recent literature suggests an expanding role for radiologists in obtaining biopsies using an ultrasound (US)-guided technique. The present study was undertaken study to determine if the two techniques produced liver biopsy specimens of similar quality and hypothesized that at our institution, non-US-guided percutaneous liver biopsies for HCV would be of higher quality than US-guided specimens

Primary Adenocarcinoma in an Enterocutaneous Fistula Associated with Crohn’s Disease

Increasing numbers of intestinal adenocarcinomas in patients with Crohn’s disease have been reported, but the strength of this association still needs to be elucidated. Adenocarcinoma has also been documented in different types of fistulous tracts associated with Crohn’s disease. The first case of well-differentiated mucinous adenocarcinoma involving only enterocutaneous fistulae is reported in a patient with long-standing Crohn’s disease complicated by persistent abdominal wall fistulous tracts. The malignant lesion arose from neoplastic transformation of columnar epithelium lining portions of the fistulae occurring as a result of either re-epithelialization of these inflammatory tracts or mural implantation of mucosal tissue secondary to prior ulceration. The patient has remained disease-free eight years after surgical resection of the tumour. Even though intestinal carcinoma is not as strongly associated with Crohn’s disease as with ulcerative colitis, intestinal carcinoma should be considered in the setting of long-standing disease, previous intestinal exclusion surgeries and complications such as enterocutaneous or other types of fistulous tracts. The prognosis of such patients may be excellent with early diagnosis and treatment

Fatal hemorrhage from a gastroaortic fistula secondary to gastric ulceration associated with Nissen fundoplication and nonsteroidal anti-inflammatory drug use

Acute gastrointestinal hemorrhage from a gastroaortic fistula in the gastric fundoplication pouch is a rare complication of Nissen fundoplication. The present case reports a gastroaortic fistula secondary to gastric ulceration associated with prior Nissen fundoplication and nonsteroidal anti-inflammatory drug use. A 55-year-old man presented with massive hematemesis and died of exsanguination during emergency laparotomy. Recognition of factors that predispose a patient to gastric ulceration after fundoplication, including nonsteroidal anti-inflammatory drug use, is critical to arouse the high index of suspicion required to diagnose and manage this life-threatening complication