AxoDetect: an automated nerve image segmentation and quantification workflow for computational nerve modeling.

Objective.Bioelectronic treatments targeting near-organ innervation have unprecedented clinical applications. Particularly in the spleen, the inhibition of the cholinergic inflammatory response by near-organ nerve stimulation has potential to replace pharmacological treatments in chronic and autoimmune diseases. A caveat is that the optimization of therapeutic stimulation parameters relies onin vivoexperimentation, which becomes challenging due to the small nerve diameters (2 µm), complex anatomy, and mixed axon type composition of the autonomic nerves. Effective development ofin silicomodels requires tools which allow for fast and efficient quantification of axonal composition of specific nerves. Current approaches to generate such information rely on manual image segmentation and quantification.Approach.We developed a combined image-segmentation and model-generation software called AxoDetect: a target- and format-agnostic computer vision algorithm which can segment myelin, endo/epineurium, and both myelinated and unmyelinated fibers from a nerve image without training.Main results.AxoDetect is over 10 times faster on average when compared with current automatic methods while maintaining flexibility through the use of tunable pixel threshold filters to detect different types of tissue. When compared to a distribution-based and a manually segmented model of the splenic nerve terminal branch 1, the model generated with AxoDetect had comparable threshold prediction and was able to accurately detect an increase in activation threshold caused by the addition of surrounding fat tissue to the modeled nerve.Significance.AxoDetect contributes to the acceleration of neuromodulation treatment development through faster model design and iteration without requiring training. Furthermore, the computer vision approach and tunable nature of the filters in our method allow for its use in a variety of histological applications. Our approach will impact not only the study of nerves but also the design of implantable neural interfaces to enhance bioelectronic therapeutic options.

Outcome of adult patients receiving parenteral support at home: 36 years' experience at a tertiary referral centre.

BACKGROUND AND AIMS: Patients with intestinal failure often need long-term home parenteral support (PS). We aimed to determine how the underlying diagnosis, complications and survival had changed over the last 36 years in the UK's largest IF centre. METHODS: 978 adult home PS patient records were analysed from January 1979 until October 2016. The age, sex, underlying aetiology, complications and survival was compared over 5-year periods. RESULTS: Pre-1990 to 2011-2016, numbers increased from 29 to 451, the mean age of patients increased from 31 ± 16.5 to 52 ± 17.6 years. The percentage of patients with IF due to surgical complications increased (3.4%-28.8%, p < 0.001)), while those with inflammatory bowel disease decreased (37.9%-22.6%, p < 0.001). Complication of home PS reduced: catheter related blood stream infections (CRBSI) 71.4% to 42,2%, CVC thrombosis 34.5%-5.3%. Intestinal failure associated liver disease (IFLAD) 10.3%-1.8%. Patients with dysmotility, scleroderma and a congenital aetiology had the highest incidence of CRBSI and CVC Thrombosis. Overall survival was greater pre-1995 [HR 0.2-0.4 (p = 0.02)] most likely associated with an increase in mean age. Survival for patients without malignancy was 90%, 66%, 55%, 45%, 33% and 25% at 1,5, 10, 15, 20 and 30 years respectively. Multivariate analysis demonstrated a relationship between survival and age of starting home PS; type of home PS; presence or absence of the colon in continuity; and underlying aetiology. CONCLUSION: Demand for home PS is increasing in particular for advanced malignancy, post-surgical complications and older more co-morbid patients. Complications of home PS are reducing over the last 30 years and 10-year survival for non-malignant aetiologies improving. Survival and changes in aetiology in intestinal failure.

Brain-stimulation induced blindsight: unconscious vision or response bias?

A dissociation between visual awareness and visual discrimination is referred to as "blindsight". Blindsight results from loss of function of the primary visual cortex (V1) which can occur due to cerebrovascular accidents (i.e. stroke-related lesions). There are also numerous reports of similar, though reversible, effects on vision induced by transcranial Magnetic Stimulation (TMS) to early visual cortex. These effects point to V1 as the "gate" of visual awareness and have strong implications for understanding the neurological underpinnings of consciousness. It has been argued that evidence for the dissociation between awareness of, and responses to, visual stimuli can be a measurement artifact of the use of a high response criterion under yes-no measures of visual awareness when compared with the criterion free forced-choice responses. This difference between yes-no and forced-choice measures suggests that evidence for a dissociation may actually be normal near-threshold conscious vision. Here we describe three experiments that tested visual performance in normal subjects when their visual awareness was suppressed by applying TMS to the occipital pole. The nature of subjects' performance whilst undergoing occipital TMS was then verified by use of a psychophysical measure (d') that is independent of response criteria. This showed that there was no genuine dissociation in visual sensitivity measured by yes-no and forced-choice responses. These results highlight that evidence for visual sensitivity in the absence of awareness must be analysed using a bias-free psychophysical measure, such as d', In order to confirm whether or not visual performance is truly unconscious.

Assessment of long chain n-3 polyunsaturated fatty acid status and clinical outcome in adults receiving home parenteral nutrition.

BACKGROUND & AIMS: Long term parenteral nutrition rarely supplies the long chain n-3 polyunsaturated fatty acids (PUFA), eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA). The aim of this study was to assess long chain n-3 PUFA status in patients receiving home parenteral nutrition (HPN). METHODS: Plasma phospholipid fatty acids were measured in 64 adult HPN patients and compared with 54 age, sex and BMI matched controls. Logistic regression analysis was used to identify factors related to plasma fatty acid fractions in the HPN patients, and to identify factors associated with the risk of clinical complications. RESULTS: Plasma phospholipid fractions of EPA, DPA and DHA were significantly lower in patients receiving HPN. Factors independently associated with low fractions included high parenteral energy provision, low parenteral lipid intake, low BMI and prolonged duration of HPN. Long chain n-3 PUFA fractions were not associated with incidence of either central venous catheter associated infection or central venous thrombosis. However, the fraction of EPA were inversely associated with plasma alkaline phosphatase concentrations. CONCLUSIONS: This study demonstrates abnormal long chain n-3 PUFA profiles in patients receiving HPN. Reduced fatty acid intake may be partly responsible. Fatty acid metabolism may also be altered.

Managing liver dysfunction in parenteral nutrition.

Parenteral nutrition is life saving in patients with intestinal failure but liver dysfunction is commonly encountered, especially in neonates. Although abnormal liver function tests associated with short-term parenteral nutrition are usually benign and transient, liver dysfunction in both children and adults receiving long-term parenteral nutrition can progress to end-stage liver disease and liver failure. The aetiology of parenteral nutrition-associated liver disease is complex and multifactorial, with a range of patient, disease and nutrition-related factors implicated. Sepsis is of particular importance, as is the lack of enteral nutrition and overfeeding with intravenous glucose and/or lipid. Deficiencies of a number of amino acids including choline and taurine have also been implicated. Management of hepatic dysfunction in parenteral nutrition should initially focus on preventing its occurrence. Sepsis should be managed appropriately, enteral nutrition should be encouraged and maximised where possible and parenteral overfeeding should be avoided. Provision of parenteral lipid should be optimised to prevent the adverse effects of both deficiency and excess, and cyclical rather than continuous parenteral feeding should be administered. There is some evidence of benefit in neonates from oral antibiotics to prevent intestinal bacterial overgrowth and from oral ursodeoxycholic acid, but less to support their use in adults. Similarly, data to support widespread use of parenteral choline or taurine supplementation are lacking at present. Ultimately, severe parenteral nutrition-associated liver disease may necessitate referral for small intestine and/or liver transplantation.

Nontuberculous mycobacterial adenitis: effectiveness of chemotherapy following incomplete excision.

BACKGROUND: Management of lymphadenopathy caused by nontuberculous mycobacteria (NTM) is primarily surgical. Where this cannot achieve sufficient clearance of infected nodes, chemotherapy is often given. AIM: This study compared results of surgery alone with surgery followed by chemotherapy in instances where there was incomplete surgical removal of diseased tissue. METHODS: Chemotherapy comprised azithromycin 10 mg/kg and rifabutin 6 mg/kg both given once daily for 6 mo. Ninety-eight children with NTM infection were seen in the period 1990-2004. Sixty-eight cases with adenopathy where "time to healing" (discharge stopped and inflammation settled) was known were available to compare response to treatment. RESULTS: The median (range) "time to healing" in weeks for 43 patients who had surgery alone was: incision and drainage (I&D)/curettage 6 (1-72) (n = 10); excision 3 (1-28) (n = 22); and from the last operation of multiple (repeat) surgery 3 (1-40) (n = 11). For 25 patients who required chemotherapy in addition to surgery, the median (range) "time to healing" in weeks was I&D/curettage 10 (1-40) (n = 17), excision 14 (8-20) (n = 2) and multiple surgery 29 (2-88) (n = 6). CONCLUSION: In children with adenitis due to NTM, where surgical resection is followed by continued discharge and inflammation, chemotherapy should be considered before further surgery is undertaken.

Artificial nutrition: principles and practice of enteral feeding.

Enteral feeding is a commonly used form of nutritional supplementation for patients with intestinal failure, both in hospitals and in the community. This article concentrates on the basic principles of enteral feeding, including the physiological effects of feeding into the intestinal tract. It covers the indications for enteral feeding, the different methods of supplying enteral feeds to the gastrointestinal tract, and the potential complications. There is also a discussion of the indications for and practice of home enteral nutrition.

The metabolic response to intravenous medium-chain triglycerides in infants after surgery.

OBJECTIVE: The aim of this study was to determine if administration of mixed medium-chain triglycerides (MCT)/long chain triglycerides (LCT) fat emulsion would increase net fat oxidation and if carbohydrate intake would influence net fat oxidation. STUDY DESIGN: Stable infants receiving total parenteral nutrition were studied after surgery. Respiratory gas exchange was measured by indirect calorimetry and urinary nitrogen excretion by the micro-Kjeldahl method. Intravenous fat (4 g/kg/day) was given as either pure LCT fat emulsion or 50/50 MCT/LCT fat emulsion. Carbohydrate intake was either "high" (15 g/kg/day) or "low" (10 g/kg/day). Four groups of patients were studied: group 1 = LCT and high-carbohydrate; group 2 = LCT and low-carbohydrate; group 3 = MCT/LCT and high-carbohydrate; group 4 = MCT/LCT and low-carbohydrate. RESULTS: At a carbohydrate intake of 15 g/kg/day, the calories available from glucose exceeded the measured resting energy expenditure (REE), and no differences were seen in either energy expenditure or net fat oxidation between patients receiving LCT and MCT/LCT fat emulsions. However, at a carbohydrate intake of 10 g/kg/day, when glucose calories were less than REE, net fat oxidation was significantly higher in patients receiving MCT/LCT (median, 1.94; range, 1.05-2.24 g/kg/day) compared with patients receiving LCT (median, 0.60; range, -0.09 to 1.35; P =.03). CONCLUSION: Providing that carbohydrate calories do not exceed REE, partial replacement of LCT by MCT in intravenous fat emulsions can increase net fat oxidation in infants after surgery.

Localization and endothelin-3 dependence of stem cells of the enteric nervous system in the embryonic colon.

BACKGROUND/PURPOSE: The aganglionosis in a variable length of the distal gut found in Hirschsprung's disease results from the abnormal prenatal development of neural crest-derived stem cells of the enteric nervous system. The cytokine endothelin-3 is necessary for successful colonization of the distal gut, but the location of this interaction with neural crest-derived stem cells remains to be established. The hypothesis tested here is that the stem cells of the enteric nervous system (ENS) in the colon are located at the leading edge of the migrating wave of neural crest-derived stem cells and that these cells require colonic endothelin-3 for complete colonization of the gut. METHODS: Explants of 11.5-day-old embryonic intact mouse gut and isolated colon were cultured for 72 hours in the presence and absence of the endothelin-B receptor antagonist, BQ788. Specimens then were sectioned and stained by immunohistochemistry to assess enteric nervous system development. RESULTS: Isolated colon contained a very low number (mean, 73 cells; range, 37 to 106; n = 8) of neural crest-derived stem cells, which had just entered its proximal end at the leading edge of neural crest cell migration. After 72 hours of culture, progeny of these few neural crest-derived stem cells had colonized the colon at an equivalent ganglionic density to those in intact gut. Furthermore, neuronal differentiation, as shown by the appearance of nitric oxide synthase positive neurons, also was equivalent to intact gut. Blockade of the endothelin-B receptor produced terminal aganglionosis in both isolated colons and intact gut. CONCLUSIONS: The very small number of cells that first enter the proximal colon at the leading edge of neural crest cell migration have the ability to colonize the entire colon normally in an ET-3-dependent manner. These cells therefore have the functional characteristics expected of the stem cells of the colonic enteric nervous system. Furthermore, the normal development of these cells is dependent on the endothelin-3 expressed by the mesenchymal cells of the colon itself.

Analysis of the effects of endothelin-3 on the development of neural crest cells in the embryonic mouse gut.

BACKGROUND/PURPOSE: Mutations in the endothelin-3 (ET-3) and endothelin-B receptor (EDNR-B) genes cause terminal colonic aganglionosis in mice and are linked to Hirschsprung's disease. These experiments are designed to determine if the development of terminal enteric ganglia depends on changes in proliferation, apoptosis, or differentiation of enteric neural crest (NC) cells in response to ET-3. METHODS: Gut from embryonic lethal-spotted mice (lacking ET-3) and controls were investigated in vivo. NC-derived cells were identified immunohistochemically and their proliferation, apoptosis and differentiation monitored by bromodeoxyuridine incorporation, the terminal deoxytransferase poly dU nick end labelling (TUNEL) reaction, and appearance of neuronal nitric oxide synthase (NOS), respectively. RESULTS: No differences in apoptosis or proliferation of NC cells were apparent between lethal-spotted embryos and controls. Although no temporal differences in the differentiation of NOS neurones were evident, these cells appeared more cranially in the gut in the absence of ET-3 than in controls. CONCLUSIONS: ET-3 has no detectable influence on proliferation, apoptosis, or timing of differentiation of NC-derived cells in the gut. However, the more proximal location of differentiated neurones in the absence of ET-3 is consistent with a restricted role in migration of NC-derived cells.