Trends and Sociodemographic Patterns in Keratoconus Management 2015-2020: An American Academy of Ophthalmology IRIS® Registry Analysis

PURPOSE

Investigate trends in keratoconus (KCN) treatment patterns and diagnosis age from 2015 to 2020 and evaluate sociodemographic associations with the treatment approach.

DESIGN

Retrospective cohort study.

PARTICIPANTS

Patients with a new KCN diagnosis from 2015 to 2020 were identified in the Academy IRIS® Registry (Intelligent Research in Sight).

METHODS

Associations between sociodemographic factors and treatment were evaluated using multivariable logistic regression.

MAIN OUTCOME MEASURES

Outcomes included percentages and rates of each treatment (collagen crosslinking [CXL], keratoplasty, or no procedure) from 2015 to 2020, age at diagnosis during this period, and sociodemographic factors associated with treatment type.

RESULTS

A total of 66 199 patients with a new diagnosis of KCN were identified. The percentage of patients undergoing CXL increased from 0.05% in 2015 to 29.5% in 2020 (P = 0.008). The average age (standard deviation) of KCN patients decreased from 44.1 (±16.9) years in 2015 to 39.2 (±16.9) years in 2020 (P < 0.001). In multivariable analyses comparing CXL versus no procedure and keratoplasty versus no procedure, patients undergoing CXL tended to be younger with the odds of having CXL decreasing with increasing age, for example, comparing CXL and no procedure patients, using ages 0-20 years as reference, the odds ratio (OR) (95% confidence interval [CI]) decreased from 0.62 (0.57-0.67; P < 0.0001) for patients aged 21-40 years to 0.03 (0.02-0.04; P < 0.0001) for patients aged > 60 years. Men were more likely than women to have CXL (OR, 1.31; 95% CI, 1.23-1.40; P < 0.0001) and keratoplasty (OR, 1.30; 95% CI, 1.19-1.42; P < 0.0001). Black patients were less likely than White patients to have CXL (OR, 0.70; 95% CI, 0.63-0.77; P < 0.0001) and more likely to have keratoplasty (OR, 2.24; 95% CI, 2.01-2.50; P < 0.0001). Likewise, Hispanic patients had higher odds of CXL (OR, 1.12; 95% CI, 1.00-1.24; P < 0.05) and keratoplasty (OR, 1.29; 95% CI, 1.12-1.50; P < 0.001) compared with non-Hispanic patients. Collagen crosslinking and keratoplasty also varied by region and insurance status.

CONCLUSIONS

A significant increase in use of CXL was noted from 2015 to 2020. Sociodemographic differences in treatment among KCN patients may reflect differences in access, use, or care patterns, and future studies should aim to identify strategies to improve access for all patients.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Disparities in Retinal Vein Occlusion Presentation and Initiation of Anti-VEGF Therapy: An Academy IRIS® Registry Analysis

OBJECTIVE

Investigate disparities in retinal vein occlusion (RVO) presentation and initiation of anti-VEGF treatment.

DESIGN

Retrospective cohort study.

SUBJECTS

Patients in the American Academy of Ophthalmology IRIS® (Intelligent Research in Sight) Registry database (2015-2021) with branch or central RVO and macular edema (ME).

METHODS

The association of demographic characteristics and presenting visual acuity (VA) with anti-VEGF treatment initiation were quantified using multivariable logistic regression.

MAIN OUTCOME MEASURES

Treatment with ≥ 1 anti-VEGF injection within 12 months after RVO diagnosis.

RESULTS

A total of 304 558 eligible patients with RVO and ME were identified. Age at presentation varied by race, ethnicity, sex, and RVO type (all P values < 0.001). Within the first year after RVO presentation, 192 602 (63.2%) patients received ≥ 1 anti-VEGF injection. In a multivariable regression model adjusting for relevant covariates, female (vs. male) patients had lower odds of receiving injections (odds ratio [OR], 0.95; 95% confidence interval [CI], 0.93-0.96; P < 0.0001) as did Black/African American (vs. White) patients (OR, 0.90; 95% CI, 0.88-0.92; P < 0.0001) and Asian (vs. White) patients (OR, 0.95; 95% CI, 0.91-0.99; P = 0.02), whereas older patients (vs. patients aged < 51 years) had higher odds (61-70 years: OR, 1.20; 95% CI, 1.16-1.24; 71-80 years: OR, 1.20; 95% CI, 1.16-1.24; > 80 years: OR, 1.15; 95% CI, 1.11-1.18; all P values < 0.0001). Hispanic (vs. non-Hispanic) patients had a small increased odds of treatment initiation (OR, 1.08; 95% CI, 1.04-1.11; P < 0.0001). Results were similar in the subset of 226 143 patients with VA data. In this subset, patients with presenting VA < 20/40 to 20/200 were most frequently treated in the first year after diagnosis (∼ 70%) and patients with light perception/no light perception (LP-NLP) vision or VA of 20/20 or better were treated least frequently (36.9% and 41.9%, respectively).

CONCLUSIONS

In this large national clinical registry, 37% of RVO patients with ME had no anti-VEGF treatment documented in the first year after diagnosis. Black/African American, Asian, and female patients and patients with VA of LP-NLP were least likely to receive treatment. Awareness of this undertreatment and these disparities highlight the need for initiatives to ensure all RVO patients receive timely anti-VEGF injections for optimized visual outcomes.

FINANCIAL DISCLOSURES

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Investigating clot-flow interactions by integrating intravital imaging with in silico modeling for analysis of flow, transport, and hemodynamic forces

As a blood clot forms, grows, deforms, and embolizes following a vascular injury, local clot-flow interactions lead to a highly dynamic flow environment. The local flow influences transport of biochemical species relevant for clotting, and determines the forces on the clot that in turn lead to clot deformation and embolization. Despite this central role, quantitative characterization of this dynamic clot-flow interaction and flow environment in the clot neighborhood remains a major challenge. Here, we propose an approach that integrates dynamic intravital imaging with computer geometric modeling and computational flow and transport modeling to develop a unified in silico framework to quantify the dynamic clot-flow interactions. We outline the development of the methodology referred to as Intravital Integrated In Silico Modeling or IVISim, and then demonstrate the method on a sample set of simulations comprising clot formation following laser injury in two mouse cremaster arteriole injury model data: one wild-type mouse case, and one diYF knockout mouse case. Simulation predictions are verified against experimental observations of transport of caged fluorescent Albumin (cAlb) in both models. Through these simulations, we illustrate how the IVISim methodology can provide insights into hemostatic processes, the role of flow and clot-flow interactions, and enable further investigations comparing and contrasting different biological model scenarios and parameter variations.

Incidence and Risk Factors for Retinal Detachment and Retinal Tear after Cataract Surgery: IRIS® Registry (Intelligent Research in Sight) Analysis

Objective

To report the incidence of and evaluate demographic, ocular comorbidities, and intraoperative factors for rhegmatogenous retinal detachment (RRD) and retinal tear (RT) after cataract surgery in the American Academy of Ophthalmology IRIS® Registry (Intelligent Research in Sight).

Design

Retrospective cohort study.

Participants

Patients aged ≥ 40 years who underwent cataract surgery between 2014 and 2017.

Methods

Multivariable logistic regression was used to evaluate demographic, comorbidity, and intraoperative factors associated with RRD and RT after cataract surgery.

Main Outcome Measures

Incidence and risk factors for RRD or RT within 1 year of cataract surgery.

Results

Of the 3 177 195 eyes of 1 983 712 patients included, 6690 (0.21%) developed RRD and 5489 (0.17%) developed RT without RRD within 1 year after cataract surgery. Multivariable logistic regression odds ratios (ORs) showed increased risk of RRD and RT, respectively, among men (OR 3.15; 95% confidence interval [CI], 2.99-3.32; P < 0.001 and 1.79; 95% CI, 1.70-1.89; P < 0.001), and younger ages compared with patients aged > 70, peaking at age 40 to 50 for RRD (8.61; 95% CI, 7.74-9.58; P < 0.001) and age 50 to 60 for RT (2.74; 95% CI, 2.52-2.98; P < 0.001). Increased odds of RRD were observed for procedure eyes with lattice degeneration (LD) (10.53; 95% CI, 9.82-11.28; P < 0.001), hypermature cataract (1.61; 95% CI, 1.06-2.45; P = 0.03), complex cataract surgery (1.52; 95% CI, 1.4-1.66; P < 0.001), posterior vitreous detachment (PVD) (1.24; 95% CI, 1.15-1.34; P < 0.001), and high myopia (1.2; 95% CI, 1.14-1.27; P < 0.001). Lattice degeneration conferred the highest odds of RT (43.86; 95% CI, 41.39-46.49; P < 0.001).

Conclusion

In the IRIS Registry, RRD occurs in approximately 1 in 500 cataract surgeries in patients aged > 40 years within 1 year of surgery. The presence of LD conferred the highest odds for RRD and RT after surgery. Additional risk factors for RRD included male gender, younger age, hypermature cataract, PVD, and high myopia. These data may be useful during the informed consent process for cataract surgery and help identify patients at a higher risk of retinal complications.

Financial Disclosures

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Open-Globe Injury Repairs in the American Academy of Ophthalmology IRIS® Registry 2014 - 2018: Incidence, Risk Factors, and Visual Outcomes

PURPOSE

To estimate incidence and evaluate demographic risk factors and visual acuity (VA) outcomes of open-globe injuries requiring surgical repair in the IRIS® Registry (Intelligent Research in Sight).

DESIGN

Retrospective cohort study.

PARTICIPANTS

Patients with open-globe injury repairs (OGRs) were identified by Current Procedural Terminology codes (65275, 65280, 65285, 65286, 65235, 65260, and 65265) from 2014 through 2018 in the IRIS Registry.

METHODS

Logistic regression models adjusting for age, sex, race, ethnicity, United States region, concurrent and subsequent surgeries, and baseline VA.

MAIN OUTCOME MEASURES

Outcomes included annual and 5-year incidence rates per 100 000 people and factors associated with OGR, VA better than 20/40, and VA of 20/200 or worse at final follow-up (3-12 months after OGR).

RESULTS

Thirteen thousand seven hundred sixty-six OGRs were identified; 5-year cumulative incidence was 28.0 per 100 000 patients. Open-globe repair was associated with age 21 to 40 years compared with younger than 21 years (odds ratio [OR], 1.6; 95% confidence interval [CI], 1.5-1.7]), male sex (OR, 2.8; 95% CI, 2.7-2.9), Black versus White race (OR, 1.3; 95% CI, 1.2-1.4), Hispanic versus non-Hispanic ethnicity (OR, 1.7; 95% CI, 1.6-1.8), and South (OR, 1.4; 95% CI, 1.3-1.5) and West (OR, 1.3; 95% CI, 1.2-1.4) versus Midwest regions and associated inversely with Asian versus White race (OR, 0.6; 95% CI, 0.6-0.7). Visual acuity outcomes, analyzed in a subset of 2966 patients with VA data available, showed vision impairment (VA < 20/40) at final follow-up was associated with VA of 20/200 or worse at presentation (20/200 better than 20/40; OR, 11.1; 95% CI, 8.0-15.7), older age (e.g., > 80 years vs. < 21 years; OR, 5.8; 95% CI, 3.2-10.7), and Black versus White race (OR, 1.8; 95% CI, 1.3-2.6). Risk factors were similar for VA of 20/200 or worse after OGR. Among the 1063 patients undergoing OGR with VA of 20/200 or worse at presentation, VA did not improve to better than 20/200 at follow-up in 35% of patients (1063/2996).

CONCLUSIONS

Our findings bring to light racial disparities in risk of OGR and poor visual outcomes that warrant further exploration.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found after the references.

Thrombin spatial distribution determines protein C activation during hemostasis and thrombosis

Rebalancing the hemostatic system by targeting endogenous anticoagulant pathways, like the protein C (PC) system, is being tested as a means of improving hemostasis in patients with hemophilia. Recent intravital studies of hemostasis demonstrated that, in some vascular contexts, thrombin activity is sequestered in the extravascular compartment. These findings raise important questions about the context-dependent contribution of activated PC (APC) to the hemostatic response, because PC activation occurs on the surface of endothelial cells. We used a combination of pharmacologic, genetic, imaging, and computational approaches to examine the relationships among thrombin spatial distribution, PC activation, and APC anticoagulant function. We found that inhibition of APC activity, in mice either harboring the factor V Leiden mutation or infused with an APC-blocking antibody, significantly enhanced fibrin formation and platelet activation in a microvascular injury model, consistent with the role of APC as an anticoagulant. In contrast, inhibition of APC activity had no effect on hemostasis after penetrating injury of the mouse jugular vein. Computational studies showed that differences in blood velocity, injury size, and vessel geometry determine the localization of thrombin generation and, consequently, the extent of PC activation. Computational predictions were tested in vivo and showed that when thrombin generation occurred intravascularly, without penetration of the vessel wall, inhibition of APC significantly increased fibrin formation in the jugular vein. Together, these studies show the importance of thrombin spatial distribution in determining PC activation during hemostasis and thrombosis.

The contribution of TFPIα to the hemostatic response to injury in mice

BACKGROUND

Tissue factor pathway inhibitor (TFPI) is an essential regulator of coagulation, limiting thrombin generation and preventing thrombosis. In humans and mice, TFPIα is the sole isoform present in platelets.

OBJECTIVE

Here, we asked whether TFPIα, because of its release from platelets at sites of injury, has a unique role in limiting the hemostatic response.

METHODS

TFPIα-mutant (TfpiΔα/Δα ) mice were generated by introducing a stop codon in the C-terminus. Platelet accumulation, platelet activation, and fibrin accumulation were measured following penetrating injuries in the jugular vein and cremaster muscle arterioles, and imaged by fluorescence and scanning electron microscopy. Time to bleeding cessation was recorded in the jugular vein studies.

RESULTS

TfpiΔα/Δα mice were viable and fertile. Plasma TFPI levels were normal in the TfpiΔα/Δα mice, no TFPI protein or activity was present in their platelets and thrombin-antithrombin complex levels were indistinguishable from Tfpi+/+ littermates. There was a small, but statistically significant reduction in the time to bleeding cessation following jugular vein puncture injury in the TfpiΔα/Δα mice, but no measurable changes in platelet or fibrin accumulation or in hemostatic plug architecture following injury of the micro- or macrovasculature.

CONCLUSION

Loss of TFPIα expression does not produce a global prothrombotic state in mice. Platelet TFPIα is expected to be released or displayed in a focal manner at the site of injury, potentially accumulating to high concentrations in the narrow gaps between platelets. If so, the data from the vascular injury models studied here indicate this is not essential for a normal hemostatic response in mice.

A Human Vascular Injury-on-a-Chip Model of Hemostasis

Hemostasis is an innate protective mechanism that plays a central role in maintaining the homeostasis of the vascular system during vascular injury. Studying this essential physiological process is often challenged by the difficulty of modeling and probing the complex dynamics of hemostatic responses in the native context of human blood vessels. To address this major challenge, this paper describes a microengineering approach for in vitro modeling of hemostasis. This microphysiological model replicates the living endothelium, multilayered microarchitecture, and procoagulant activity of human blood vessels, and is also equipped with a microneedle that is actuated with spatial precision to simulate penetrating vascular injuries. The system recapitulates key features of the hemostatic response to acute vascular injury as observed in vivo, including i) thrombin-driven accumulation of platelets and fibrin, ii) formation of a platelet- and fibrin-rich hemostatic plug that halts blood loss, and iii) matrix deformation driven by platelet contraction for wound closure. Moreover, the potential use of this model for drug testing applications is demonstrated by evaluating the effects of anticoagulants and antiplatelet agents that are in current clinical use. The vascular injury-on-a-chip may serve as an enabling platform for preclinical investigation of hematological disorders and emerging therapeutic approaches against them.

Use of electron microscopy to study platelets and thrombi

Electron microscopy has been a valuable tool for the study of platelet biology and thrombosis for more than 70 years. Early studies using conventional transmission and scanning electron microscopy (EM) provided a foundation for our initial understanding of platelet structure and how it changes upon platelet activation. EM approaches have since been utilized to study platelets and thrombi in the context of basic, translational and clinical research, and they are instrumental in the diagnosis of multiple platelet function disorders. In this brief review, we provide a sampling of the many contributions EM based studies have made to the field, including both historical highlights and contemporary applications. We will also discuss exciting new imaging modalities based on EM and their utility for the study of platelets, hemostasis and thrombosis into the future.

Novelty Improves the Formation and Persistence of Memory in a Naturalistic School Scenario

One of the top challenges in education and neuroscience consists in translating laboratory results into strategies to improve learning and memory in teaching environments. In that sense, during the last two decades, researchers have discovered specific temporal windows around learning, during which the intervention with some experiences induces modulatory effects on the formation and/or persistence of memory. Based on these results, the aim of the present study was to design a specific strategy to improve the memory of students in a high-school scenario, by assessing the effect of a novel situation experienced close to learning. We found that the long-term memory about a geometrical figure was more precise in the group of students that faced a novel situation 1 h before or after learning the figure than the control group of students who did not face the novelty. This enhancement was probably triggered by processes acting on memory formation mechanisms that remained evident 45 days after learning, indicating that the improvement was sustained over time. In addition, our results showed that novelty no longer improved the memory if it was experienced 4 h before or after learning. However, far beyond this window of efficacy, when it was faced around 10 h after learning, the novel experience improved the memory persistence tested 7 days later. In summary, our findings characterized different temporal windows of the effectiveness of novelty acting on memory processing, providing a simple and inexpensive strategy that could be used to improve memory formation and persistence in high-school students.

Regulation of Platelet Activation and Coagulation and Its Role in Vascular Injury and Arterial Thrombosis

Hemostasis requires tightly regulated interaction of the coagulation system, platelets, blood cells, and vessel wall components at a site of vascular injury. Dysregulation of this response may result in excessive bleeding if the response is impaired, and pathologic thrombosis with vessel occlusion and tissue ischemia if the response is robust. Studies have elucidated the major molecular signaling pathways responsible for platelet activation and aggregation. Antithrombotic agents targeting these pathways are in clinical use. This review summarizes research examining mechanisms by which these multiple platelet signaling pathways are integrated at a site of vascular injury to produce an optimal hemostatic response.

Detection of Sub-fM DNA with Target Recycling and Self-Assembly Amplification on Graphene Field-Effect Biosensors

All-electronic DNA biosensors based on graphene field-effect transistors (GFETs) offer the prospect of simple and cost-effective diagnostics. For GFET sensors based on complementary probe DNA, the sensitivity is limited by the binding affinity of the target oligonucleotide, in the nM range for 20 mer targets. We report a ∼20 000× improvement in sensitivity through the use of engineered hairpin probe DNA that allows for target recycling and hybridization chain reaction. This enables detection of 21 mer target DNA at sub-fM concentration and provides superior specificity against single-base mismatched oligomers. The work is based on a scalable fabrication process for biosensor arrays that is suitable for multiplexed detection. This approach overcomes the binding-affinity-dependent sensitivity of nucleic acid biosensors and offers a pathway toward multiplexed and label-free nucleic acid testing with high accuracy and selectivity.

Platelet packing density is an independent regulator of the hemostatic response to injury

Essentials Platelet packing density in a hemostatic plug limits molecular movement to diffusion. A diffusion-dependent steep thrombin gradient forms radiating outwards from the injury site. Clot retraction affects the steepness of the gradient by increasing platelet packing density. Together, these effects promote hemostatic plug core formation and inhibit unnecessary growth.

SUMMARY

Background Hemostasis studies performed in vivo have shown that hemostatic plugs formed after penetrating injuries are characterized by a core of highly activated, densely packed platelets near the injury site, covered by a shell of less activated and loosely packed platelets. Thrombin production occurs near the injury site, further activating platelets and starting the process of platelet mass retraction. Tightening of interplatelet gaps may then prevent the escape and exchange of solutes. Objectives To reconstruct the hemostatic plug macro- and micro-architecture and examine how platelet mass contraction regulates solute transport and solute concentration in the gaps between platelets. Methods Our approach consisted of three parts. First, platelet aggregates formed in vitro under flow were analyzed using scanning electron microscopy to extract data on porosity and gap size distribution. Second, a three-dimensional (3-D) model was constructed with features matching the platelet aggregates formed in vitro. Finally, the 3-D model was integrated with volume and morphology measurements of hemostatic plugs formed in vivo to determine how solutes move within the platelet plug microenvironment. Results The results show that the hemostatic mass is characterized by extremely narrow gaps, porosity values even smaller than previously estimated and stagnant plasma velocity. Importantly, the concentration of a chemical species released within the platelet mass increases as the gaps between platelets shrink. Conclusions Platelet mass retraction provides a physical mechanism to establish steep chemical concentration gradients that determine the extent of platelet activation and account for the core-and-shell architecture observed in vivo.

Abstract 530: Hemostasis Revisited: a Combined Light and Electron Microscopy Analysis of Hemostatic Plug Formation in vivo

We have previously shown in the microcirculation that gradients of platelet agonists develop during the hemostatic response as a consequence of the solute transport properties within the evolving platelet mass. These agonist gradients result in the formation of a gradient of platelet activation extending from the site of vascular injury. Here we utilized a combined light and electron microscopy approach to examine the organization of hemostatic plugs formed in response to larger injuries that result in significant bleeding in the mouse jugular vein. The results show that the hemostatic response to vessel wall puncture in a large vein is similarly characterized by a gradient of platelet activation. Specifically, we found that 1) platelets are the primary cellular component of hemostatic plugs in large veins; 2) platelet activation is heterogeneous, with fully activated and degranulated platelets present at the interface of the damaged vessel wall and extending to the extravascular side of hemostatic plugs, while platelets aggregated on the luminal side of plugs were minimally activated; 3) fibrin, and by extension thrombin activity, is localized primarily in the extravascular space; 4) P2Y 12 antagonism impairs platelet aggregation, resulting in a prolonged bleeding time when the hole created by the puncture injury does not completely fill with platelets; and 5) the importance of P2Y 12 signaling in establishing a hemostatically competent plug is related to the size of the hole through which blood escapes the vasculature. Taken together, these results provide novel insights into the mechanisms of hemostatic plug formation in vivo, demonstrate in detail the mechanism by which P2Y 12 antagonists result in bleeding, and highlight differences in the composition and morphology of hemostatic plugs versus pathologic thrombi.

Abstract 363: Platelet Mass Retraction is a Negative Feedback Regulator of Thrombin Generation and Activity

Endogenous anticoagulants, including antithrombin III, tissue factor pathway inhibitor, and activated protein C (aPC) provide a biochemical means to inhibit thrombin generation and/or activity. In addition, we have previously shown that platelet mass retraction prevents the escape and exchange of solutes, thereby providing a biophysical mechanism to limit thrombin generation and activity. The relative contribution of each of these biochemical and biophysical mechanisms to the termination of thrombin activity during the hemostatic response in vivo remains poorly understood. Here, using computational simulations coupled with in vivo experimental models, we tested the hypotheses that 1) platelet mass retraction itself is physiologically relevant to inhibit thrombin generation; and 2) that given the spatial localization of protein C activation on the endothelial cell surface, aPC mediated thrombin inhibition has negligible effects on the hemostatic response. Our computational model has several innovative aspects, including 3D representations of the vessel, extravascular space, and injury, blood flow, and a simplified but anatomically correct model of coagulation. Our simulations show that tissue factor localization combined with flow exiting the injury limit thrombin generation/activity to the extravascular space. Our experiments using a mouse jugular puncture injury model show rich deposition of fibrin in the extravascular space and little to no fibrin in the luminal side. Additionally, our simulations illustrate how platelet mass retraction inhibits thrombin generation by decreasing the delivery of substrates, such as prothrombin and factor X, and at the same time it limits thrombin activity by constraining its movement. These effects are mediated by physical forces only and are independent of the biochemical inhibitory pathways. Our in vivo experiments using aPC inhibitory antibodies show that lack of aPC mediated thrombin inhibition has negligible effects on the hemostatic response. In conclusion, this study suggests that platelet mass retraction is an underappreciated mechanism that negatively regulates thrombin generation, while aPC mediated inhibition of thrombin generation plays a minor role in hemostasis.

Abstract 40: Platelet Fragmentation During the Hemostatic Response and its Prevention by a P2Y12 Antagonist

Previous studies using intravital microscopy have shown that hemostatic plugs formed in the mouse microvasculature have a characteristic architecture in which the extent of platelet activation reflects gradients in the distribution of platelet agonists radiating outwards from the injury site. In that setting, we found minimal overlap of thrombin and ADP signaling, with thrombin primarily responsible for robust platelet activation close to the injury site and P2Y 12 -mediated ADP signaling resulting in accumulation of minimally activated platelets. Here we have taken these studies a major step forward by integrating fluorescence with scanning electron microscopy. Hemostatic plugs produced by needle injury in mouse jugular veins were imaged in situ 1 to 20 min after injury. The results show with unprecedented detail what could only be inferred previously, showing that platelet size, morphology and packing density vary remarkably depending on spatial localization within the hemostatic plug. The intraluminal and extravascular portions of the hemostatic mass presented distinct architectures. A large mass comprised almost exclusively of platelets was observed on the interior surface of the vein. Platelets closest to the injury edge had a highly activated morphology, including P-selectin surface expression, dense packing and platelet fragmentation, while those farther from the injury edge often remained discoid. In contrast, the extravascular portion of the hemostatic mass was rich in densely-packed, platelet-derived fragments intertwined with fibrin. Hemostatic plugs from mice treated with a P2Y 12 inhibitor were significantly smaller. The platelet activation gradient described above was less apparent and, notably, fragmentation of the platelets close to the injury edge was not observed with the inhibitor present. In conclusion, our findings indicate that 1) the development of a platelet activation gradient is a conserved feature of the hemostatic response across different vessels, 2) fragmentation of platelets closest to the injury site occurs very rapidly following injury, and 3) clinically relevant platelet signaling pathways play a role in regulating its formation.

Computational identification and analysis of signaling subnetworks with distinct functional roles in the regulation of TNF production

Inflammation is a complex process driven by the coordinated action of a vast number of pro- and anti-inflammatory molecular mediators. While experimental studies have provided an abundance of information about the properties and mechanisms of action of individual mediators, essential system-level regulatory patterns that determine the time-course of inflammation are not sufficiently understood. In particular, it is not known how the contributions from distinct signaling pathways involved in cytokine regulation combine to shape the overall inflammatory response over different time scales. We investigated the kinetics of the intra- and extracellular signaling network controlling the production of the essential pro-inflammatory cytokine, tumor necrosis factor (TNF), and its anti-inflammatory counterpart, interleukin 10 (IL-10), in a macrophage culture. To tackle the intrinsic complexity of the network, we employed a computational modeling approach using the available literature data about specific molecular interactions. Our computational model successfully captured experimentally observed short- and long-term kinetics of key inflammatory mediators. Subsequent model analysis showed that distinct subnetworks regulate IL-10 production by impacting different temporal phases of the cAMP response element-binding protein (CREB) phosphorylation. Moreover, the model revealed that functionally similar inhibitory control circuits regulate the early and late activation phases of nuclear factor κB and CREB. Finally, we identified and investigated distinct signaling subnetworks that independently control the peak height and tail height of the TNF temporal trajectories. The knowledge of such subnetwork-specific regulatory effects may facilitate therapeutic interventions aimed at precise modulation of the inflammatory response.

Minimum wound size for clotting: flowing blood coagulates on a single collagen fiber presenting tissue factor and von Willebrand factor

It is unknown if a lower size limit exists for human blood coagulation under flow over physiological vessel wall triggers as small as a single collagen fiber. Prior determinations of the smallest sized surface stimuli necessary for clotting of human blood, defined as the patch size threshold, have not deployed whole blood, hemodynamic flow, and platelet adhesive stimuli. For whole blood perfused in microfluidic devices, we report that steady venous flow (wall shear rate, 100 s(-1)) was sufficient to drive platelet deposition on 20 micron long zones of collagen fibers or on a single fiber. With tissue factor (TF)-coated collagen, flowing blood generated robust platelet deposits, platelet-localized thrombin, and fibrin on a single collagen fiber, thus demonstrating the absence of a physiological patch size threshold under venous flow. In contrast, at arterial wall shear rate (1000 s(-1)) with TF present, essentially no platelet or fibrin deposition occurred on 20 micron collagen zones or on a single collagen fiber, demonstrating a patch threshold, which was overcome by pre-coating the collagen with von Willebrand factor (vWF). For venous flows, human blood can clot on one of the smallest biological units of a single collagen fiber presenting TF. For arterial flows, vWF together with TF allows human blood to generate thrombin and fibrin on a patch stimulus as limited as a single collagen fiber. vWF-dependent platelet adhesion represents a particle-based sensing mechanism of micron-scale stimuli that then allows amplification of the molecular components of TF-driven thrombin and fibrin production under arterial flow.

Increased platelet storage time is associated with mitochondrial dysfunction and impaired platelet function

BACKGROUND

Hemorrhagic shock is a leading cause of death following severe trauma, and platelet transfusions are frequently necessary to achieve hemostasis. Platelets, however, require special storage conditions, and storage time has been associated with loss of platelet quality. We hypothesized that standard storage conditions have a deleterious effect on platelet mitochondrial function and platelet activation.

MATERIALS AND METHODS

Platelet donations were collected from healthy donors (n = 5) and stored in gas-permeable collection bags according to American Association of Blood Bank recommendations. Platelet units were sampled from day of collection (day 0) until day 7. High-resolution respirometry was used to assess baseline mitochondrial respiration, maximal oxygen utilization, and individual mitochondrial complex-dependent respiration. Fluorescence-activated cell sorting was performed to analyze mitochondrial content, mitochondrial reactive oxygen species, the expression of P-selectin (both before and after challenge with thrombin receptor-activating peptide), and apoptosis. Data were analyzed using analysis of variance and Pearson correlation (P < 0.05 significant).

RESULTS

Mitochondrial respiration decreased significantly in platelets stored longer than 2 d (P < 0.05). Platelets also demonstrated a persistent decrease in response to stimulation with thrombin receptor-activating peptide by the third day of storage (P < 0.05) as well as an increase in mitochondrial reactive oxygen species and apoptosis (P < 0.05). Mitochondrial respiration significantly correlated with platelet capacity to activate (r = 0.8, P < 0.05).

CONCLUSIONS

Platelet mitochondrial respiratory function and activation response decrease significantly in platelets stored for 3 d or more. Because platelet transfusions almost universally occur between the third and fifth day of storage, our findings may have significant clinical importance and warrant further in vivo analysis.

Models of electrical activity: calibration and prediction testing on the same cell

Mathematical models are increasingly important in biology, and testability is becoming a critical issue. One limitation is that one model simulation tests a parameter set representing one instance of the biological counterpart, whereas biological systems are heterogeneous in their properties and behavior, and a model often is fitted to represent an ideal average. This is also true for models of a cell's electrical activity; even within a narrowly defined population there can be considerable variation in electrophysiological phenotype. Here, we describe a computational experimental approach for parameterizing a model of the electrical activity of a cell in real time. We combine the inexpensive parallel computational power of a programmable graphics processing unit with the flexibility of the dynamic clamp method. The approach involves 1), recording a cell's electrical activity, 2), parameterizing a model to the recording, 3), generating predictions, and 4), testing the predictions on the same cell used for the calibration. We demonstrate the experimental feasibility of our approach using a cell line (GH4C1). These cells are electrically active, and they display tonic spiking or bursting. We use our approach to predict parameter changes that can convert one pattern to the other.

Harnessing the platelet signaling network to produce an optimal hemostatic response

Once released into the circulation by megakaryocytes, circulating platelets can undergo rapid activation at sites of vascular injury and resist unwarranted activation, which can lead to heart attacks and strokes. Historically, the signaling mechanisms underlying the regulation of platelet activation have been approached as a collection of individual pathways unique to agonist. This review takes a different approach, casting platelet activation as the product of a signaling network, in which activating and restraining mechanisms interact in a flexible network that regulates platelet adhesiveness, cohesion between platelets, granule secretion, and the formation of a stable hemostatic thrombus.

Two types of burst firing in gonadotrophin-releasing hormone neurones

Gonadotrophin-releasing hormone (GnRH) neurones fire spontaneous bursts of action potentials, although little is understood about the underlying mechanisms. In the present study, we report evidence for two types of bursting/oscillation driven by different mechanisms. Properties of these different types are clarified using mathematical modelling and a recently developed active-phase/silent-phase correlation technique. The first type of GnRH neurone (1-2%) exhibits slow (∼0.05 Hz) spontaneous oscillations in membrane potential. Action potential bursts are often observed during oscillation depolarisation, although some oscillations were entirely subthreshold. Oscillations persist after blockade of fast sodium channels with tetrodotoxin (TTX) and blocking receptors for ionotropic fast synaptic transmission, indicating that they are intrinsically generated. In the second type of GnRH neurone, bursts were irregular and TTX caused a stable membrane potential. The two types of bursting cells exhibited distinct active-phase/silent-phase correlation patterns, which is suggestive of distinct mechanisms underlying the rhythms. Further studies of type 1 oscillating cells revealed that the oscillation period was not affected by current or voltage steps, although amplitude was sometimes damped. Oestradiol, an important feedback regulator of GnRH neuronal activity, acutely and markedly altered oscillations, specifically depolarising the oscillation nadir and initiating or increasing firing. Blocking calcium-activated potassium channels, which are rapidly reduced by oestradiol, had a similar effect on oscillations. Kisspeptin, a potent activator of GnRH neurones, translated the oscillation to more depolarised potentials, without altering period or amplitude. These data show that there are at least two distinct types of GnRH neurone bursting patterns with different underlying mechanisms.

Investigating heterogeneity of intracellular calcium dynamics in anterior pituitary lactotrophs using a combined modelling/experimental approach

Cell responses are commonly heterogeneous, even within a subpopulation. In the present study, we investigate the source of heterogeneity in the Ca(2+) response of anterior pituitary lactotrophs to a Ca(2+) mobilisation agonist, thyrotrophin-releasing hormone. This response is characterised by a sharp increase of cytosolic Ca(2+) concentration as a result of mobilisation of Ca(2+) from intracellular stores, followed by a decrease to an elevated plateau level that results from Ca(2+) influx. We focus on heterogeneity of the evoked Ca(2+) spike under extracellular Ca(2+) free conditions. We introduce a method that uses the information provided by a mathematical model to characterise the source of heterogeneity. This method compares scatter plots of features of the Ca(2+) response obtained experimentally with those made from the mathematical model. The model scatter plots reflect random variation of parameters over different ranges, and matching the experimental and model scatter plots allows us to predict which parameters are most variable. We find that a large degree of variation in Ca(2+) efflux is a likely key contributor to the heterogeneity of Ca(2+) responses to thyrotrophin-releasing hormone in lactotrophs. This technique is applicable to any situation in which the heterogeneous biological response is described by a mathematical model.

Correlation analysis a tool for comparing relaxation-type models to experimental data

We describe a new technique for comparing mathematical models to the biological systems that are described. This technique is appropriate for systems that produce relaxation oscillations or bursting oscillations, and takes advantage of noise that is inherent to all biological systems. Both types of oscillations are composed of active phases of activity followed by silent phases, repeating periodically. The presence of noise adds variability to the durations of the different phases. The central idea of the technique is that the active phase duration may be correlated with either/both the previous or next silent phase duration, and the resulting correlation pattern provides information about the dynamic structure of the system. Correlation patterns can easily be determined by making scatter plots and applying correlation analysis to the cluster of data points. This could be done both with experimental data and with model simulation data. If the model correlation pattern is in general agreement with the experimental data, then this adds support for the validity of the model. Otherwise, the model must be corrected. While this tool is only one test of many required to validate a mathematical model, it is easy to implement and is noninvasive.

[Anticoagulant prophylaxis in women affected by thrombophilia and previous obstetric complications]

Pregnancy is a condition of excessive clotting due to a decrease of some coagulation factors and a reduction of anticoagulant proteins, such as protein S. It is known that the causes of congenital or acquired thrombophilia may be associated with an increased risk of venous thromboembolism during pregnancy and/or obstetric complications, such early or late fetal loss, intrauterine fetal deaths, pre-eclampsia, fetal growth restriction. During pregnancy the use of a prophylaxis with antithrombotic drugs is considered at present a promising opportunity to significantly reduce the prevalence of thromboembolic complications, improving maternal and fetal outcomes. This article is a review to most recent evidence of pregnant anticoagulant prophylaxis in women with previous thromboembolic events.

Enzyme isoforms may increase phenotypic robustness

Enzyme isoforms are found in many cellular reactions, and can differ in the kind of reaction they catalyze, in their substrate affinity, or in their reaction rates. The evolutionary significance of enzyme isoforms is only partially understood. We used mathematical modeling to investigate the hypothesis that isoforms may be favored by selection because they can increase the phenotypic robustness of the system. We modify a model for circadian clock gene expression in Drosophila to incorporate the presence of isoforms in the phosphorylation pathway of the period gene. We consider the case in which different isoforms catalyze the same reaction but have different affinities for the substrate. Stability is increased if there is dynamic control of the expression of isoforms relative to each other. Thus, we show that controlling isoform proportion can be a powerful mechanism for reducing the effects of variations in the values of system parameters, increasing system robustness.

Pneumatosis coli induced by acarbose administration for diabetes mellitus. Case report and literature review

The authors report a case report of rare disease interesting the digestive tract and often associated to the other gastrointestinal pathologies and/or pulmonary diseases and can be also associated to not gastrointestinal conditions such as collagen-vascular disease, transplantation, AIDS, use of corticosteroid and chemotherapy; other causes can be iatrogenic such as traumatic gastrointestinal endoscopy (a mucoses biopsy, a polipectomy) or the assumption of lattulosio; in 15-20% of cases the pneumatosis cystoides intestinalis is considered primitive. In the our case the Pneumatosis coli was associated to administration of acarbose; in international literature only four papers in the English language were reported. Our patient showed a strongly aspecific symptomatology and easily attributable in first line or to the pathology of base (diabetic patient) or to the assumption of the acarbose; from about 7-8 months she showed unexplained episodes of crampy abdominal pain, diarrhea with 3-4 defecations/die with semiliquid and normochromic stools, tenesmus and a not better specified loss of weight. The diagnosis was been performed by colonoscopy and confirmed by abdominal CT scan with water enema and histologically; we have used the traditional radiology only to exclude the involvement of other gastroenteric districts. The patient was been treated with O2-therapy associated to antibiotics treatment; the suspension of the causal factor, the acarbose, has been of not secondary importance; the complete resolution of disease was obtained after 15 days of therapy.

[The content and structure of nursing documentation in Careggi Hospital, Florence, 1998: results and perspectives]

This retrospective, observational study was performed to evaluate the structure and the content of the nursing documentation in the Azienda ospedaliera Careggi, Firenze in 1998. To this aim we review 1964 nursing records including both notes by turns and care plans. One-thousand-one-hundred-and-twenty-five records came from surgical and 839 from medical wards. From the selected records, every day of the hospital stay, including both the admission and the discharge, were evaluated, so that the studied days were a total of 18,683. Only 32% of the nursing records had a global assessment of patient situation on admission. A medical diagnosis was observed in 84% of the cases, but a nursing diagnosis was absent in over 99.5% of the charts. During stay most notes were related to medical treatment and visits. Nursing notes were lacking in 32% of turns, while "nothing to report" was recorded in another 15.5% of cases. A nursing care plan was present in a minority of records. A final evaluation of planned nursing interventions was reported in approximately 5% of the charts. Nursing care plans were updated during stay in less than one tenth of cases. Discharges notes were absent in slightly more than 80% of the cases. This survey confirms the importance of continuing education and supervision in nursing documentations, if a reliable source of nursing information has to be developed. Future nursing records should include only essential information, avoiding any overlap with medical charts.

[Organizational appropriateness of recoveries: results of the evaluation of recoveries by AEP/PRUO at the Careggi Hospital in Florence in 1995-1998]

The organizational appropriateness of hospital stays is an expression of a hospital's efficiency and aim of the management control. The AEP (American Version)/PRUO (Italian Version) protocol is specific for measuring the organizational appropriateness of hospital stays. The aim of this study is the comparative analysis of the organizational appropriateness of hospital stays in Careggi Hospital of Florence and in all hospital Departments in 1995 and 1998. In 1998 the AEP/PRUO protocol was applied to 2148 samples of hospital stays out of 38,968 eligible hospitalizations, and in 1995 a sample of 1989 hospital stays out of 35,108. In 1998 2,148 admissions and 15,338 days of hospitalization were tested. In 1995, 1989 admission days and 12,264 days of hospitalization were tested, 63 departments were studied. In 1995 the first edition of the protocol was applied, in 1998 the second. A sample of 218 of the 1998 hospital stays was tested with both editions to evaluate the impact of differences. In 1998, with the second edition of the protocol, the inappropriateness rate of admission days and hospitalization days and the rate of in-patients inappropriate hospital stays was respectively 38.0%, 43.8% and 18.5%. Compared with 1995 results, the rates increased +6.2%, 6% and +7.5% respectively. Instead, with the first edition of the protocol, the rates were 29.7%, 37.6% and 10.7% and, compared with 1995, they were reduced -2.1%, -0.6% and -0.3%. The longitudinal multilevel analysis has allowed the evaluation of the performance of each department.

[Dolichoarteriopathy (kinking, coiling,tortuosity) of the carotid arteries and cardiovascular risk factors]

BACKGROUND AND AIMS

The clinical significance of dolichoarteriopathies (kinking, coiling, tortuosity) and their prognosis have not yet been clearly defined. A study was performed in outpatients in order to evaluate the cardiovascular risk factors of dolichoarteriopathies.

METHODS

A total of 1220 subjects (620 males and 600 females, aged between 25 and 89 years old) were examined using color Doppler ultrasonography of the extracranial carotid arteries with an Acuson 128 XP-5 scan and 7 MHz linear probe. The reason for the test was the presence of clinical symptoms or cardiovascular risk factors. The risk factors studied included: arterial hypertension [systolic (> 140 mmHg) and/or diastolic arterial pressure (> 90 mmHg)], hypercholesterolemia (total cholesterol > 200 mg/dl), diabetes mellitus, cigarette smoking. Patients were divided as follows: patients with arterial hypertension alone, patients with arterial hypertension associated with other cardiovascular risk factors (hypercholesterolemia, diabetes mellitus, smoking), patients with other cardiovascular risk factors (hypercholesterolemia, diabetes mellitus, smoking), patients without risk factors.

RESULTS

In 316 (25.9%) patients with dolichoarteriopathies, arterial hypertension alone was present in 98 (31%), arterial hypertension associated with other cardiovascular risk factors in 85 (26.3%) and other cardiovascular risk factors in 54 (17%), whereas 75 (25%) did not present cardiovascular risk factors. In the 904 subjects without dolichoarteriopathies, arterial hypertension alone was present in 254 (28%), arterial hypertension associated with other cardiovascular risk factors in 213 (23.6%) and other cardiovascular risk factors in 191 (21.1%), whereas 241 (27.2%) did not present cardiovascular risk factors. In 316 subjects with dolichoarteriopathies, cardiovascular risk factors were equally present in the two sexes without statistically significant differences. In cases with kinking and tortuosity, cardiovascular risk factors were equally present in the two sexes, whereas colling was more frequently associated with arterial hypertension alone in males and with arterial hypertension associated with other risk factors in females, showing a statistically significant difference.

CONCLUSIONS

The findings of this study reveal that the presence of risk factors in patients with dolichoarteriopathies is comparable to that in subjects without dolichoarteriopathies. Also in the three types of dolichoarteriopathies (kinking, coiling and tortuosity), cardiovascular risk factors were equally present. Therefore, these results appear to lay the role of arterial hypertension or other cardiovascular risk factors in the genesis of diolichoarteriopathies open to question.