Enhancing Understanding of the Visual Cycle by Applying CRISPR/Cas9 Gene Editing in Zebrafish

During the vertebrate visual cycle, all-trans-retinal is exported from photoreceptors to the adjacent RPE or Müller glia wherein 11-cis-retinal is regenerated. The 11-cis chromophore is returned to photoreceptors, forming light-sensitive visual pigments with opsin GPCRs. Dysfunction of this process perturbs phototransduction because functional visual pigment cannot be generated. Mutations in visual cycle genes can result in monogenic inherited forms of blindness. Though key enzymatic processes are well characterized, questions remain as to the physiological role of visual cycle proteins in different retinal cell types, functional domains of these proteins in retinoid biochemistry and in vivo pathogenesis of disease mutations. Significant progress is needed to develop effective and accessible treatments for inherited blindness arising from mutations in visual cycle genes. Here, we review opportunities to apply gene editing technology to two crucial visual cycle components, RPE65 and CRALBP. Expressed exclusively in the human RPE, RPE65 enzymatically converts retinyl esters into 11-cis retinal. CRALBP is an 11-cis-retinal binding protein expressed in human RPE and Muller glia. Loss-of-function mutations in either protein results in autosomal recessive forms of blindness. Modeling these human conditions using RPE65 or CRALBP murine knockout models have enhanced our understanding of their biochemical function, associated disease pathogenesis and development of therapeutics. However, rod-dominated murine retinae provide a challenge to assess cone function. The cone-rich zebrafish model is amenable to cost-effective maintenance of a variety of strains. Interestingly, gene duplication in zebrafish resulted in three Rpe65 and two Cralbp isoforms with differential temporal and spatial expression patterns. Functional investigations of zebrafish Rpe65 and Cralbp were restricted to gene knockdown with morpholino oligonucleotides. However, transient silencing, off-target effects and discrepancies between knockdown and knockout models, highlight a need for more comprehensive alternatives for functional genomics. CRISPR/Cas9 in zebrafish has emerged as a formidable technology enabling targeted gene knockout, knock-in, activation, or silencing to single base-pair resolution. Effective, targeted gene editing by CRISPR/Cas9 in zebrafish enables unprecedented opportunities to create genetic research models. This review will discuss existing knowledge gaps regarding RPE65 and CRALBP. We explore the benefits of CRISPR/Cas9 to establish innovative zebrafish models to enhance knowledge of the visual cycle.

Short communication: Variability in milk urea nitrogen and dairy total mixed ration composition in the northeastern United States

The main objective of this survey was to examine variability in milk urea nitrogen (MUN) for Dairy Herd Improvement Association (DHIA) herds in the northeastern United States (the Northeast), examine trends in dairy cow diet composition, and determine potential relationships for MUN and diet composition. Trends in milk fat and protein concentrations, milk yield, days in milk on test day, and lactation number of the cows were also evaluated. The data set for the survey included 10,839,461 DHIA dairy cow records from 2004 to 2015 for 13 states (CT, DE, MA, MD, ME, NH, NJ, NY, PA, RI, VA, VT, and WV) and was retrieved from Dairy Records Management Systems (Raleigh, NC). Average (across states and years) milk yield, milk fat, and milk protein were 31.6 ± 0.24 kg/d, 3.85 ± 0.021%, and 3.13 ± 0.013%, respectively. No obvious trends were observed for milk fat or protein content, but milk yield steadily increased during the survey period. Milk urea N concentration averaged 13.3 ± 0.13 mg/dL, with no obvious or consistent trends. Examination of variability in dairy feed cost and all milk price for the Northeast indicated that high MUN generally coincided with high feed cost and high milk price. For the diet composition survey, 9,707 records of total mixed ration (TMR) analyses, unrelated to the milk composition data set, from the Cumberland Valley Analytical Service (Maugansville, MD) database were examined. Concentration of TMR crude protein (CP) decreased from 17.1% in 2007 to 16.4% in 2015, but there was not an obvious trend in soluble protein concentration. Concentration of TMR neutral detergent fiber (NDF) and 24-h in vitro NDF degradability declined steadily during the survey period and was accompanied by a steady increase in TMR starch concentration. Examination of these unrelated data sets revealed lack of correlation between MUN and diet chemical composition. Thus, we conclude that individual cow MUN in Northeast dairy herds fluctuated between 2004 and 2015. It appeared that MUN followed variability in feed cost; however, ration feed ingredient data were not available to better define the reasons for the variations in MUN.

Radiation dose from common radiological investigations and cumulative exposure in children with cystic fibrosis: an observational study from a single UK centre

OBJECTIVES

Cumulative radiation exposure is associated with increased risk of malignancy. This is important in cystic fibrosis (CF) as frequent imaging is required to monitor disease progression and diagnose complications. Previous estimates of cumulative radiation are outdated as the imaging was performed on older equipment likely to deliver higher radiation. Our objectives were to determine the radiation dose delivered to children during common radiological investigations using modern equipment and to identify the number of such investigations performed in a cohort of children with CF to calculate their cumulative radiation exposure.

DESIGN, SETTING AND PARTICIPANTS

Data including age at investigation and radiation exposure measured as estimated effective dose (EED) were collected on 2827 radiological studies performed on children at one UK paediatric centre. These were combined with the details of all radiological investigations performed on 65 children with CF attending the same centre to enable calculation of each child's cumulative radiation exposure.

RESULTS

The mean EED for the common radiological investigations varied according to age. The range was 0.01-0.02 mSv for chest X-rays, 0.03-0.11 mSv for abdominal X-rays, 0.57-1.69 mSv for CT chest, 2.9-3.9 mSv for abdominal and pelvic CT, 0.20-0.21 mSv for sinus CT and 0.15-0.52 mSv for fluoroscopy-guided procedures. The mean EED was three to five times higher for helical compared with axial chest CT scans. The mean annual cumulative EED for our cohort of children with CF was 0.15 mSv/year with an estimated cumulative paediatric lifetime EED (0-18 years) of 3.5 mSv.

CONCLUSIONS

This study provides up-to-date estimations of the radiation exposure when using common radiological investigations. These doses and the estimates of cumulative radiation exposure in children with CF are lower than previously reported. This reflects the reduced EED associated with modern equipment and the use of age-specific scanning protocols.

Diabetes Worsens Functional Outcomes in Young Female Rats: Comparison of Stroke Models, Tissue Plasminogen Activator Effects, and Sexes

Diabetes worsens stroke outcome and increases the risk of hemorrhagic transformation (HT) after ischemic stroke, especially with tissue plasminogen activator (tPA) treatment. The widespread use of tPA is still limited by the fear of hemorrhagic transformation (HT), and underlying mechanisms are actively being pursued in preclinical studies. However, experimental models use a 10 times higher dose of tPA than the clinical dose (10 mg/kg) and mostly employ only male animals. In this translational study, we hypothesized that low-dose tPA will improve the functional recovery after the embolic stroke in both control and diabetic male and female animals. Diabetes was induced in age-matched male and female Wistar rats with high fat diet and low-dose streptozotocin (30 mg/kg, i.p.). Embolic stroke was induced with clot occlusion of the middle cerebral artery (MCA). The animals were treated with or without tPA (1 mg/kg, i.v.) at 90 min after surgery. An additional set of animals were subjected to 90 min MCAO with suture. Neurological deficits (composite score and adhesive removal test-ART), infarct size, edema ratio, and HT index were assessed 3 days after surgery. In the control groups, female rats had smaller infarcts and better functional outcomes. tPA decreased infarct size in both sexes with a greater effect in males. While there was no difference in HT between males and females without tPA, HT was less in the female + tPA group. In the diabetic groups, neuronal injury increased in females reaching that of the infarct sizes seen in male rats. tPA decreased infarct size in females but not males. HT was greater in female rats than in males and was not further increased with tPA. Diabetes worsened neurological deficits in both sexes. Male animals showed improved sensorimotor skills, especially with tPA treatment, but there was no improvement in females. These data suggest that diabetes amplifies neurovascular injury and neurological deficits in both sexes. Human dose tPA offers some degree of protection in male but not female rats. Given that control female animals experience less injury compared to male rats, the diabetes effect is more profound in females.

TLR2 knockout protects against diabetes-mediated changes in cerebral perfusion and cognitive deficits

The risk of cognitive decline in diabetes (Type 1 and Type 2) is significantly greater compared with normoglycemic patients, and the risk of developing dementia in diabetic patients is doubled. The etiology for this is likely multifactorial, but one mechanism that has gained increasing attention is decreased cerebral perfusion as a result of cerebrovascular dysfunction. The innate immune system has been shown to play a role in diabetic vascular complications, notably through the Toll-like receptor (TLR)-stimulated release of proinflammatory cytokines and chemokines that lead to vascular damage. TLR2 has been implicated in playing a crucial role in the development of diabetic microvascular complications, such as nephropathy, and thus, we hypothesized that TLR2-mediated cerebrovascular dysfunction leads to decreased cerebral blood flow (CBF) and cognitive impairment in diabetes. Knockout of TLR2 conferred protection from impaired CBF in early-stage diabetes and from hyperperfusion in long-term diabetes, prevented the development of endothelium-dependent vascular dysfunction in diabetes, created a hyperactive and anxiolytic phenotype, and protected against diabetes-induced impairment of long-term hippocampal and prefrontal cortex-mediated fear learning. In conclusion, these findings support the involvement of TLR2 in the pathogenesis of diabetic vascular disease and cognitive impairment.

Abstract WMP81: Low Dose tPA Worsens The Short Term Outcomes After Thromboembolic Stroke In Both Male And Female Diabetic Animals

Diabetes worsens stroke outcome and increases the risk of hemorrhagic transformation (HT) after ischemic stroke, especially with tPA treatment. We previously showed that low dose tPA decreased infarct size and improved functional outcome in both male and female control rats with embolic stroke. In the current study, we hypothesized that low dose tPA will also improve the functional recovery after the embolic stroke in both male and female animals with diabetes. Diabetes was induced in age matched male and female Wistar rats with high fat diet and low dose streptozotocin (30 mg/kg, i.p.). Embolic stroke was induced with middle cerebral artery occlusion. The animals were treated with or without tPA (1 mg/kg, i.v.) at 90 min after surgery. Neurological deficits (composite score and adhesive removal test-ART), infarct size, edema ratio, and HT index were assessed 3 days after surgery. The blood flow has increased in the tPA treated animals in the first 1 to 1.5 hr after treatment. The infarct size and edema was not significantly different in untreated animals, but HT was greater in female diabetic rats. The tPA treatment worsened HT in both genders with no change in infarct size. Decline in ART was worsened with tPA treatment in both sexes. Our data suggest that the low dose tPA after ischemic stroke has detrimental effects on the cerebrovascular recovery and functional outcome in both male and female animals with diabetes.

Abstract WP294: Deferoxamine Treatment Improves Outcomes After Embolic Stroke in Diabetic Rats

Diabetes increases the risk of hemorrhagic transformation (HT) after a cerebral ischemic event, a major factor limiting the use of tissue plasminogen activator (tPA) for stroke patients. We previously showed that increased HT is associated with poorer recovery in diabetes. In the current study, we hypothesized that excess iron contributes to poor recovery and that iron chelation with deferoxamine (DFX) will improve the neurological recovery after embolic stroke in diabetes. Diabetes was induced with high fat diet and low dose streptozotocin injection (30 mg/kg) in male Wistar rats. Both control and diabetes animals were subjected to embolic stroke with middle cerebral artery occlusion and sacrificed 2 weeks after the surgery. DFX (100 mg/kg) or vehicle was given every 12 h for 7 days after stroke. The composite score (Bederson’s score and beam walk), adhesive removal (ART) and novel object recognition (NOR) were assessed at day 1, 3, 7 and 14 after the surgery. DFX reduced mortality in diabetes. Diabetic animals displayed poor outcomes. By Day 14, DFX reduced motor and cognitive deficits in diabetes but not in controls. These results suggest that iron chelation therapy may improve outcomes after ischemic stroke in this high risk population.

Abstract WP291: Diabetes Impairs Long-term Functional Recovery in an Embolic Stroke Model in Sex Independent Manner

Ischemic stroke is a leading cause of death and disability. Diabetes not only increases the risk of stroke, it also worsens the outcomes, increases the risk of hemorrhagic transformation (HT) and impairs recovery after stroke. It is well established that young females are more protected and show better outcomes than males after stroke. However, the impact of diabetes on long term recovery after stroke in both sexes was not clear. Accordingly, this study tested the hypothesis that diabetes impairs long term functional recovery after ischemic stroke in a sex independent manner.

Methods: Diabetes was induced in male and female Wistar rats using high fat diet and low dose streptozotocin (30 mg/Kg). After 8 weeks of diabetes, animals were subjected to embolic stroke. Male and female Wistar normoglycemic age matched rats were used as controls. Motor (composite score: 14 best outcome and adhesive removal-ART) and cognitive (novel object recognition, NOR) deficits were assessed at day1, 3, 7 and 14.

Results: Female control animals had better outcomes compared to the males. Mortality was higher in diabetic animals, especially in males. The neurological deficits were greater in diabetic animals with no difference between males and females.

Conclusion: Diabetes impaired functional and cognitive outcome and recovery after ischemic stroke in a sex independent manner.

Effects of Exendin-4 on human adipose tissue inflammation and ECM remodelling

BACKGROUND/OBJECTIVES:

Subjects with type-2 diabetes are typically obese with dysfunctional adipose tissue (AT). Glucagon-like peptide-1 (GLP-1) analogues are routinely used to improve glycaemia. Although, they also aid weight loss that improves AT function, their direct effect on AT function is unclear. To explore GLP-1 analogues' influence on human AT's cytokine and extracellular matrix (ECM) regulation, we therefore obtained and treated omental (OMAT) and subcutaneous (SCAT) AT samples with Exendin-4, an agonist of the GLP-1 receptor (GLP-1R).

SUBJECTS/METHODS:

OMAT and abdominal SCAT samples obtained from women during elective surgery at the Royal Devon & Exeter Hospital (UK) were treated with increasing doses of Exendin-4. Changes in RNA expression of adipokines, inflammatory cytokines, ECM components and their regulators were assessed and protein secretion analysed by ELISA. GLP-1R protein accumulation was compared in paired AT depot samples.

RESULTS:

Exendin-4 induced an increase in OMAT adiponectin (P=0.02) and decrease in elastin expression (P=0.03) in parallel with reduced elastin secretion (P=0.04). In contrast to OMAT, we did not observe an effect on SCAT. There was no change in the expression of inflammatory markers (CD14, TNFA, MCP-1), collagens, TGFB1 or CTGF. GLP-1R accumulation was higher in SCAT.

CONCLUSIONS:

Independently of weight loss, which may bias findings of in vivo studies, GLP-1 analogues modify human OMAT physiology favourably by increasing the insulin-sensitising cytokine adiponectin. However, the reduction of elastin and no apparent effect on AT's inflammatory cytokines suggest that GLP-1 analogues may be less beneficial to AT function, especially if there is no associated weight loss.

Cerebrovascular complications of diabetes: focus on cognitive dysfunction

The incidence of diabetes has more than doubled in the United States in the last 30 years and the global disease rate is projected to double by 2030. Cognitive impairment has been associated with diabetes, worsening quality of life in patients. The structural and functional interaction of neurons with the surrounding vasculature is critical for proper function of the central nervous system including domains involved in learning and memory. Thus, in this review we explore cognitive impairment in patients and experimental models, focusing on links to vascular dysfunction and structural changes. Lastly, we propose a role for the innate immunity-mediated inflammation in neurovascular changes in diabetes.

Nurses’ Net needs

More and more healthcare professionals are becoming experienced in the use of the Internet and having seen some of the resources available they are now becoming able to identify the sorts of features which would be useful to them.

This paper describes a study to identify what United Kingdom (UK) nurses, midwives and health visitors want from an Internet service dedicated to their needs. An online questionnaire was used to find out their views as to the importance of various possible content areas and to enable them to make comments.

Data were obtained from 126 self-selecting respondents over two months, and the study is ongoing. Initial results revealed wide variations in the areas that were seen as being important and in the sorts of services they would find useful from the Internet; there were, however, some consistent themes. Respondents felt that speciality information, peer-reviewed articles and bibliographic databases were the most important areas and that job advertisements, local information and mailing lists were the least important.

The importance of these results for future investment in and development of an Internet service for this group of users is considered.

The development of NMAP - the UK’s gateway to high quality Internet resources in nursing, midwifery and allied health

This paper describes the development of NMAP, a UK academic gateway to high quality Internet resources for nurses, midwives and allied health professions - an important component of the development of flexible and multi-professional learning. The rationale underlying the development is described, along with some of the issues and processes involved. Initial usage data are included, which show that there was a need for the service and that it is well used. An initial user evaluation was undertaken during November-December 2001 with over 600 users completing an online questionnaire; some preliminary data and analysis are presented. The paper concludes by examining future plans and developments.

Abstract TP277: Diabetes Amplifies Vascular Injury and Worsens Ischemic Stroke Outcome in Young Female Rats: Loss of Protection

Women are protected from stroke until they reach menopause in part due to neuroprotection conferred by sex hormones. We and others have shown that that diabetes increases neurovascular injury and worsens stroke outcomes in males. Given the clinical evidence that diabetes increases stroke risk especially in younger individuals and females, we hypothesized that diabetes worsens stroke outcome even in young females. We further postulated that moderate hyperglycemia worsens hemorrhagic transformation (HT) and outcomes independent of changes in infarct size. High fat diet plus low dose streptozotocin model of diabetes was used. Control and diabetic weight-matched male and female rats (10-12 weeks old, n=5-7) were subjected to embolic stroke with a fibrin-rich humanized clot. Neurological deficits (Bederson score, adhesive removal test -ART and grip strength), infarct size, HT index, and edema ratio were assessed 3 days after surgery (Table). As expected in the control group, females rats had smaller infarct size, less edema, and better functional outcomes as compared to male rats. In the diabetic group, however, HT score was greater and this was more profound in females. Diabetes worsened the functional outcome to a much greater extent in females. While there was partial improvement of neurological deficits by Day 3 in control animals, diabetic animals did not improve but worsened. Additional studies will explore the long-term effects and the underlying mechanisms contributing to worse outcome in young and old diabetic females.

Abstract TMP115: Diabetes-induced Neuronal Degeneration and Dysfunctional Neovascularization in the Hippocampus: Implications for Cognitive Impairment and Stroke

Diabetes increases the risk of stroke and is associated with worsened cognitive outcome. We have shown that diabetes mediates immature and leaky new vessel formation in cortex and striatum and these changes are accompanied by cognitive deficits. However, the effect of diabetes on the vasculature in hippocampus, a major domain for memory and cognition, remained unknown.

Hypothesis: Impaired cognitive function in diabetes is associated with neurovascular remodeling and activation of NLRP3 inflammasome in the hippocampus.

Methods: Diabetes was induced through a high fat (45%) diet and 30mg/kg STZ injection in male Wistar rats (n=4). Vascular architecture was examined by space filling FITC. Immunohistochemistry was used to measure neuronal degeneration and NLRP3 expression. Cognitive function was assessed by novel object recognition test.

Results: Vascular density and volume were increased the dentate gyrus (DG) and CA1, respectively, in diabetic rats. The DG had reduced numbers of neurons in diabetic rats, and the CA1, CA3 and DG all showed elevated cell death. Markers of the NLRP3, ASC and cryopyrin, showed elevated expression in the hippocampus. The recognition index was decreased in diabetic animals compared to control.

Conclusions: These data suggest that the DG is sensitive to neurovascular remodeling in diabetes. Diabetes-induced NLRP3 activation may be involved in this remodeling and contribute to cognitive deficits in diabetes.

Abstract WP274: Inhibition of Na+/H+ Exchanger Isoform 1 and/or Voltage Gated Proton Channel Improves Outcomes in an Embolic Stroke Model

While Na+/H+ exchanger isoform 1 inhibitor (NHEi) has been reported to be neuro- and cardio-protective in experimental stroke and myocardial infarction, respectively, clinical use of NHEi for cardioprotection has stalled due to increased cerebrovascular events. NHEi has been demonstrated to increase Hv1 activity and we recently showed that NHEi activates NADPH oxidase and results in amplified superoxide formation in a voltage gated proton channel Hv1-dependent manner. In the CNS, Hv1 is localized primarily to microglia and deletion of Hv1 is neuroprotective after permanent and transient middle cerebral artery occlusion (MCAO). In the current study, we hypothesized that beneficial effect of NHEi after MCAO will be greater in a rat model lacking Hv1 due to loss of a potentially deleterious increase in Hv1 activation and NADPH oxidase activity. The wild type (WT) and Hv1 knockout (KO) rats (n=4-6) were treated with vehicle or NHEi (KR-32568, 2 mg/kg, i.v.) at 30 min after embolic MCAO. The neurological deficiency, infarct size, HT index, and edema ratio were assessed 3 days after surgery (Table). Compare to WT rats, KO rats had smaller infarct, less edema, and better neurological outcomes as previously found in the suture model. NHEi decreased infarct size and edema in both strains. While there was no significant difference in HT between WT and KO rats, the HT was less in WT rats with NHEi. Functional outcomes were significantly improved with NHEi in WT group, while the KO groups had a trend for a better outcomes with NHEi. These data indicate that NHE inhibition in the acute stroke period is similarly effective in both WT and Hv1 KO animals in providing neurovascular protection. Our data do not support the hypothesis that a deleterious increase in Hv1 dependent NADPH oxidase activity limits the beneficial actions of NHEi in embolic stroke. Further studies are needed to explore the underlying mechanism of the interaction between NHEi and the Hv1 channel in ischemic stroke.

Abstract 169: Human Dose tPA Improves Functional Outcomes in Both Sexes in Embolic Model of Stroke: Differential Effect on Hemorrhagic Transformation

Tissue plasminogen activator (tPA) is the only FDA-approved therapeutic agent for the treatment of acute ischemic stroke. The widespread use of tPA is still limited by the fear of hemorrhagic transformation (HT) and underlying mechanisms are actively being pursued in preclinical studies. However, experimental models use a 10 times higher dose of tPA than the clinical dose (10 mg/kg) and mostly employ only male animals. In this translational study, we hypothesized that low dose tPA would achieve clot lysis, decrease neurovascular injury and improve functional outcomes in both sexes. Aged-matched male and female Wistar rats (n=5-7) have been treated with or without tPA (1 mg/kg, i.v.) at 90 min after embolic middle cerebral artery occlusion with a fibrin-rich humanized clot. The neurological deficiency (Bederson score and adhesive removal test -ART), infarct size, HT index, and edema ratio were assessed 3 days after surgery (Table). Compared to male rats, female rats had smaller infarct size and better functional outcomes as previously reported in the literature. tPA decreased infarct size in both sexes. tPA reduced edema in males with no effect in females. While there was no difference in HT between males and females without tPA, HT was less in the female + tPA group. Functional outcomes, especially ART, were significantly improved with tPA in both sexes. These data suggest that 1) thrombolysis with a low dose tPA is effective in improving short term outcomes in both sexes, and 2) better functional outcomes in females are further enhanced with tPA. Additional studies are in progress to explore long term effects and the impact of therapeutic window, age and sex steroids on outcomes as well as the underlying mechanisms contributing to less HT in females.

The clinical anatomy of cystic artery variations: a review of over 9800 cases

PURPOSE

While laparoscopic cholecystectomy can be a routine procedure when biliary anatomy is normally located, cystic artery variations can easily disorientate the inexperienced surgeon to the anatomy of the hepatobiliary triangle. This study presents the clinically important anatomical variations of the cystic artery.

METHODS

PubMed, Medline, Cochrane Database of Systematic Reviews, and Google Scholar databases were searched to conduct a review of the existing English literature on the clinically important cystic artery variations. An aberrant vessel was defined as a vessel that originated from an atypical source and/or one that was present in a specimen in addition to the normal vessel.

RESULTS

The cystic artery originated typically from the right hepatic artery (79.02 %) and was found in the hepatobiliary triangle in only 5427 of 6661 (81.5 %) cases. Clinically important cystic artery variations are (1) the cystic artery located anterior to the common hepatic duct or common bile duct found in 485 of 2704 (17.9 %) and 228 of 4202 (5.4 %) of cases, respectively, (2) the cystic artery located inferior to the cystic duct found in 38 of 770 (4.9 %) of cases, (3) short cystic arteries found in 98 of 1037 (9.5 %) cases and (4) multiple cystic arteries found in (8.9 %) of cases.

CONCLUSION

These variations are common in the general population and can lead to inadvertent ligation of biliary ducts or aberrant vessels. Therefore, it is important for the hepatobiliary surgeon to be aware of these vascular anomalies to avoid operative complications.