A Novel Model for a Student-Led Surgical Anatomy Seminar.

OBJECTIVE: We describe a novel educational model for a student-led anatomy interest group that utilizes an efficient method of knowledge sharing among peers in order to supplement the standard gross anatomy curriculum and expose medical students to advanced, surgically relevant anatomy. DESIGN: Student leaders of the Advanced Anatomy Interest Group compile a list of advanced anatomy "tidbits" related to a topic within a particular surgical specialty. Each medical student participant signs up for a different "tidbit" and prepares a short presentation. On meeting day, students present to the group. After each presentation, a surgical faculty moderator offers feedback and provides additional surgical perspective. SETTING: Duke University School of Medicine, Durham, NC, USA. PARTICIPANTS: Three third year medical student interest group leaders, 20 first through fourth year medical student participants, and 1 surgical faculty moderator. RESULTS: Twelve students presented an advanced anatomy tidbit, and 15 students responded to a 10-question postmeeting survey. Over 90% of respondents either agreed or strongly agreed that their understanding of surgically relevant anatomy had improved. Of those students who presented, 100% agreed or strongly agreed that their preparedness to briefly teach complex medical topics to colleagues had improved. Additionally, students reported increased interest in surgery and an improved perception of surgeons. CONCLUSIONS: This novel educational model appears to be an effective and efficient way to supplement the standard gross anatomy curriculum and expose medical students to advanced, surgically relevant anatomy. In addition, this model enables students to hone their presentation skills, gain experience teaching advanced medical concepts to peers, and develop relationships with surgical faculty. Surgical faculty are also not burdened with any preparatory responsibilities, making their participation more feasible. This model can serve as a template for medical students, house staff, and faculty interested in expanding anatomy education at their own institutions.

Time to Presentation after Symptom Onset in Endophthalmitis: Clinical Features and Visual Outcomes.

PURPOSE: To investigate the impact of time from symptom onset to presentation on the clinical course and outcomes of eyes with endophthalmitis. DESIGN: Retrospective, longitudinal cohort study. PARTICIPANTS: One hundred thirty-three eyes of 130 patients with endophthalmitis. METHODS: Adults diagnosed with endophthalmitis at the Duke Eye Center from January 1, 2009, through January 1, 2018, were identified using the Duke Enterprise Data Unified Content Explorer. Patient demographics, time of symptom onset, presenting clinical features, management, and outcomes were recorded by retrospective review. Patients were divided into those seeking medical care either early (within 2 days) or later (delayed, i.e., 3 days or longer) with regard to symptom onset. Clinical features, management, and visual outcomes of eyes with early or delayed presentation were compared. MAIN OUTCOME MEASURES: Mean corrected visual acuity (VA) at presentation and at 6 months. RESULTS: In eyes with delayed presentation, VA was significantly worse on initial examination (delayed, 20/2941 vs. early, 20/1124; P = 0.009) and at 6 months (delayed, 20/547 vs. early, 20/173; P = 0.01). When controlling for time to presentation, VA before endophthalmitis was correlated significantly with VA at 6 months (Pearson r = 0.55; R2 = 29%; P < 0.0001). Eyes with glaucoma drainage device-related endophthalmitis were more likely to have a delayed presentation (P = 0.03). Eyes with delayed presentation were more likely to have conjunctival injection on initial examination (delayed, 73% vs. early, 52%; P = 0.01). Visual acuity before endophthalmitis, pain, and patient-reported blurred vision were not associated with early or delayed presentation (P > 0.05). CONCLUSIONS: Delayed presentation was associated with worse VA on initial examination and at 6 months in eyes with endophthalmitis. Presence of pain did not prompt earlier presentation. Visual acuity before endophthalmitis was associated with VA at 6 months, regardless of time to presentation. Further investigation may help to improve anticipatory guidelines for at-risk patients.

Integral role for lysyl oxidase-like-1 in conventional outflow tissue function and behavior.

Lysyl oxidase-like-1 (LOXL1), a vital crosslinking enzyme in elastin fiber maintenance, is essential for the stability and strength of elastic vessels and tissues. Variants in the LOXL1 locus associate with a dramatic increase in risk of exfoliation syndrome (XFS), a systemic fibrillopathy, which often presents with ocular hypertension and exfoliation glaucoma (XFG). We examined the role of LOXL1 in conventional outflow function, the prime regulator of intraocular pressure (IOP). Using Loxl1-/- , Loxl1+/- , and Loxl1+/+ mice, we observed an inverse relationship between LOXL1 expression and IOP, which worsened with age. Elevated IOP in Loxl1-/- mice was associated with a larger globe, decreased ocular compliance, increased outflow facility, extracellular matrix (ECM) abnormalities, and dilated intrascleral veins, yet, no dilation of arteries or capillaries. Interestingly, in living Loxl1-/- mouse eyes, Schlemm's canal (SC) was less susceptible to collapse when challenged with acute elevations in IOP, suggesting elevated episcleral venous pressure (EVP). Thus, LOXL1 expression is required for normal IOP control, while ablation results in altered ECM repair/homeostasis and conventional outflow physiology. Dilation of SC and distal veins, but not arteries, is consistent with key structural and functional roles for elastin in low-pressure vessels subjected to cyclical mechanical stress.

Divergent C-terminal motifs in Gα12 and Gα13 provide distinct mechanisms of effector binding and SRF activation.

The G12/13 subfamily of heterotrimeric guanine nucleotide binding proteins comprises the α subunits Gα12 and Gα13, which transduce signals for cell growth, cytoskeletal rearrangements, and oncogenic transformation. In an increasing range of cancers, overexpressed Gα12 or Gα13 are implicated in aberrant cell proliferation and/or metastatic invasion. Although Gα12 and Gα13 bind non-redundant sets of effector proteins and participate in unique signalling pathways, the structural features responsible for functional differences between these α subunits are largely unknown. Invertebrates encode a single G12/13 homolog that participates in cytoskeletal changes yet appears to lack signalling to SRF (serum response factor), a transcriptional activator stimulated by mammalian Gα12 and Gα13 to promote growth and tumorigenesis. Our previous studies identified an evolutionarily divergent region in Gα12 for which replacement by homologous sequence from Drosophila melanogaster abolished SRF signalling, whereas the same invertebrate substitution was fully tolerated in Gα13 [Montgomery et al. (2014) Mol. Pharmacol. 85: 586]. These findings prompted our current approach of evolution-guided mutagenesis to identify fine structural features of Gα12 and Gα13 that underlie their respective SRF activation mechanisms. Our results identified two motifs flanking the α4 helix that play a key role in Gα12 signalling to SRF. We found the region encompassing these motifs to provide an interacting surface for multiple Gα12-specific target proteins that fail to bind Gα13. Adjacent to this divergent region, a highly-conserved domain was vital for SRF activation by both Gα12 and Gα13. However, dissection of this domain using invertebrate substitutions revealed different signalling mechanisms in these α subunits and identified Gα13-specific determinants of binding Rho-specific guanine nucleotide exchange factors. Furthermore, invertebrate substitutions in the C-terminal, α5 helical region were selectively disruptive to Gα12 signalling. Taken together, our results identify key structural features near the C-terminus that evolved after the divergence of Gα12 and Gα13, and should aid the development of agents to selectively manipulate signalling by individual α subunits of the G12/13 subfamily.

Effects of sublethal UVA irradiation on activity levels of oxidative defense enzymes and protein oxidation in Escherichia coli.

When bacterial cells are stressed by a change in the environment, they respond by changing the activity of enzymes at both the transcriptional and post-transcriptional levels. The UVA component (400-315 nm) of solar radiation reaching the Earth's surface is one of the most common stresses encountered by bacteria in their environment. Bacteria have evolved various antioxidant defense systems to increase survival when subjected to the deleterious effects of UVA irradiation. Recently, UVA-induced cytotoxicity and oxidative damage have been shown to be dependent on radiation intensity and dose distribution, not just total energy dose. We now report that when Escherichia coli is subjected to continuous sublethal, low-fluence UVA irradiation (7.4 W/m(2)) while growing to stationary phase, it responds by changing the activity levels of hydroperoxidases (HPI, HPII), glutathione reductase and manganese superoxide dismutase. This leads to an attenuation of the growth-delay response and an increase resistance to lethal UVA irradiation. When E. coli is given a UVA dose of 135 kJ/m(2) delivered at a fluence rate of 50 W/m(2), extensive protein oxidation occurs which may contribute to the inhibition of key cellular enzymes, leading to cellular dysfunction, DNA damage and eventually death. Changes in antioxidant enzymes induced by low-fluence UVA irradiation do not confer greater protection from protein oxidation after a challenge dose of UVA irradiation delivered at a fluence rate of 50 W/m(2).

Reduced hydroperoxidase (HPI and HPII) activity in the Deltafur mutant contributes to increased sensitivity to UVA radiation in Escherichia coli.

In Escherichia coli, Deltafur (ferric uptake regulator) mutants are hypersensitive to various oxidative agents, including UVA radiation (400-315 nm). Studies suggest that UVA radiation mediates its biological effects on bacteria via oxidative mechanisms that lead to reactive oxygen species, including the superoxide anion radical (O2.-), hydroxyl radical (HO.), hydrogen peroxide (H2O2) and singlet oxygen (1O2). There is accumulating evidence that Fur may play an important role in the defense against UVA radiation. In addition to regulating almost all genes directly involved in iron acquisition, Fur also regulates the expression of manganese and iron superoxide dismutase (MnSOD, FeSOD), key enzymes in the defense against oxygen toxicity in E. coli. In Deltafur mutants, there is a complete absence of FeSOD. Previous results suggest that the native iron chelating agent, enterobactin, which exists in increased levels in Deltafur mutants, is an endogenous chromophore for UVA, releasing Fe2+ into the cytoplasm to catalyze the production of highly reactive hydroxyl radicals. We now report that the hypersensitivity of Deltafur mutants to UVA irradiation is associated with reduced hydroperoxidase I (HPI) and hydroperoxidase II (HPII) activity, and is associated with a decrease in the transcription of katE and katG genes. The observed decrease in HPII activity in Deltafur mutants is also associated with reduced rpoS gene transcription. This study provides additional evidence that the Fur gene product, in addition to its known regulatory effect on the expression of SOD and iron uptake mechanisms, also regulates HPI and HPII activity levels in E. coli. An H2O2-inducible antioxidant defense system leading to an increase in HPI activity, is unaltered in Deltafur mutants.