DHCR7 links cholesterol synthesis with neuronal development and axonal integrity

The DHCR7 enzyme converts 7-DHC into cholesterol. Mutations in DHCR7 can block cholesterol production, leading to abnormal accumulation of 7-DHC and causing Smith-Lemli-Opitz syndrome (SLOS). SLOS is an autosomal recessive disorder characterized by multiple malformations, including microcephaly, intellectual disability, behavior reminiscent of autism, sleep disturbances, and attention-deficit/hyperactivity disorder (ADHD)-like hyperactivity. Although 7-DHC affects neuronal differentiation in ex vivo experiments, the precise mechanism of SLOS remains unclear. We generated Dhcr7 deficient (dhcr7-/-) zebrafish that exhibited key features of SLOS, including microcephaly, decreased neural stem cell pools, and behavioral phenotypes similar to those of ADHD-like hyperactivity. These zebrafish demonstrated compromised myelination, synaptic anomalies, and neurotransmitter imbalances. The axons of the dhcr7-/- zebrafish showed increased lysosomes and attenuated autophagy, suggesting that autophagy-related neuronal homeostasis is disrupted.

Association between interatrial septum adiposity and atrial fibrillation: transesophageal echocardiography imaging and autopsy study

Recent clinical evidence has suggested that interatrial septal (IAS) adiposity contributes to atrial fibrillation (AF). The present study aimed to confirm the usefulness of transesophageal echocardiography (TEE) to estimate IAS adiposity in patients with AF. The histological IAS analysis based on autopsy samples sought to clarify characteristics that underlie the contribution of IAS adiposity to AF. The imaging study analyzed the TEE results in patients with AF (n = 184) in comparison with transthoracic echocardiography (TTE) and computed tomography (CT) results. The autopsy study histologically analyzed IAS in subjects with (n = 5) and without (n = 5) history of AF. In the imaging study, the ratio of interatrial septum adipose tissue (IAS-AT) volume per epicardial adipose tissue (EpAT) volume was greater in patients with persistent AF compared (PerAF) to those with paroxysmal AF (PAF). Multivariable analysis revealed that both TEE-assessed IAS thickness and TTE-assessed left atrial dimension were predicted by CT-assessed IAS-AT volume. In the autopsy study, the histologically-assessed IAS section thickness was greater in the AF group than that in the non-AF group and was positively correlated with the IAS-AT area percentage. In addition, the size of adipocytes in IAS-AT was smaller, compared to EpAT and subcutaneous adipose tissue (SAT). IAS-AT infiltrated into the IAS myocardium, as if adipose tissue split the myocardium (designated as myocardial splitting by IAS-AT). The number of island-like myocardium pieces as a result of myocardial splitting by IAS-AT was greater in the AF group than in the non-AF group and was positively correlated with the IAS-AT area percentage. The present imaging study confirmed the usefulness of TEE to estimate IAS adiposity in patients with AF without radiation exposure. The autopsy study suggested that the myocardial splitting by IAS-AT may contribute to atrial cardiomyopathy leading to AF.

POS1423 CHARACTERISTICS OF CYTOMEGALOVIRUS-POSITIVE VERSUS NEGATIVE, AND CYTOMEGALOVIRUS-TREATED VERSUS UNTREATED PATIENTS DURING IMMUNOSUPPRESSIVE THERAPY FOR RHEUMATIC DISEASES

Background

Immunosuppressive treatment is a common cause of cytomegalovirus (CMV) reactivation.

Objectives

To elucidate the characteristics of CMV-positive and negative patients during the treatment for rheumatic diseases.

Methods

We retrospectively evaluated consecutive patients admitted to our department from January 2006 to October 2021 whose C7-HRP antigen were measured. We collected their age, sex, primary problem and its lesion, and test results within 3 months before C7-HRP measurement. We also investigated the use of immunosuppressants, and maximum and cumulative dose of administered prednisolone within 6 months before C7-HRP measurement. Maximum and cumulative dose of prednisolone contained methylprednisolone pulse, which was converted into prednisolone equivalent. We investigated the characteristics of CMV-positive and negative patients, and those of CMV-positive patients with or without anti-CMV drug use.

Results

Of a total of 472 patients, 85 were positive and 387 were negative for C7-HRP. The average age was 71.2 vs. 64.4 (p=0.0021). Their male-to-female ratio was 20/65 vs. 120/267 (p=0.0290). The following diseases were significantly common among CMV-positive patients: microscopic polyangiitis (21.2% vs. 3.9%, p<0.0001), adult-onset Still’s disease (7.1% vs. 1.3%, p=0.0002), and systemic sclerosis (4.7% vs. 2.1%, p=0.0273). Significantly common comorbidities of CMV-positive patients were interstitial lung disease (35.3% vs. 16.0%, p<0.0001), nephritis (23.5% vs. 11.6%, p=0.0005), peripheral nervous system disorders (11.8% vs. 5.7%, p=0.0070), alveolar hemorrhage (5.9% vs. 0.8%, p=0.0001), and peripheral circulatory disorders (4.7% vs. 1.6%, p=0.0111). Average neutrophil counts (7720 /μL vs. 6440 /μL, p=0.0001), serum creatinine (1.0 mg/dL vs. 0.9 mg/dL, p=0.0104), and hemoglobin A1c (6.3% vs. 5.7%, p=0.0030) were significantly higher among CMV-positive patients, whereas hemoglobin (10.1 g/dL vs. 11.1 g/dL, p<0.0001), lymphocyte counts (820 /μL vs. 1190 /μL, p<0.0001), platelet counts (233000 /μL vs. 259000 /μL, p<0.0001), and serum albumin (2.9 g/dL vs. 3.4 g/dL, p<0.0001) were lower. Higher maximum dose of prednisolone (534.9 mg/day vs. 135.5 mg/day, p<0.0001), intravenous cyclophosphamide (27.1% vs. 11.4%, p<0.0001), rituximab (9.4% vs. 2.1%, p<0.0001), azathioprine (23.5% vs. 14.2%, p=0.0053), cyclosporin (8.2% vs. 3.6%, p=0.0101) were significantly more often used among CMV-positive patients. Average cumulative dose of prednisolone was 3022.6 mg vs. 1408.7 mg (p<0.0001). We also performed multivariate analysis, including the patients’ age, sex, maximum and cumulative dose of prednisolone, and the use of intravenous cyclophosphamide, rituximab, azathioprine, and cyclosporin. Elderly (p=0.0006), female (p=0.0293), high cumulative dose of prednisolone (p=0.0155), and the use of cyclosporin (p=0.0479) were significantly associated with CMV-positivity. Anti-CMV drug was administered to 63.5% of CMV-positive patients. The average age was significantly higher in anti-CMV-drug-treated patients than untreated patients (73.7 vs. 67.1, p=0.0492). The CMV-treated patients had significantly higher neutrophil counts (8540 /μL vs. 6280 /μL, p<0.0001), erythrocyte sedimentation rate (57.6 mm/h vs. 40.5 mm/h, p<0.0001), and C-reactive protein (5.3 mg/dL vs. 2.6 mg/dL, p<0.0001) than the untreated patients while the other data such as complete blood counts and serum chemistry revealed no significant difference. Average maximum dose of prednisolone was significantly higher in CMV-treated patients (617.1 mg/day vs. 391.1 mg/day, p=0.0261) while average cumulative dose of prednisolone and the use of any other immunosuppressants revealed no significant difference.

Conclusion

Intense immunosuppression, especially with higher dose of glucocorticoids, seemed to be the major risk factor of CMV reactivation. These medications may often require anti-CMV therapy.

Disclosure of Interests

None declared

AB0298 THE RISK OF SULPHA ALLERGY IN PATIENTS WITH RHEUMATOID ARTHRITIS

Background

Sulpha drugs have been used such as sulfasalazine for the treatment of rheumatoid arthritis (RA), and trimethoprim-sulfamethoxazole (TMP-SMX) for the treatment or prevention of pneumocystis pneumonia. However, some patients with RA delay treatment because of allergy to sulpha drugs[1]. We reported that 16.7% of RA patients presented drug allergies[2]. It was not clear what is a risk factor for drug allergies in patients with RA.

Objectives

The aim of this study was to evaluate the clinical features with sulpha allergy in patients with RA.

Methods

We prospectively examined consecutive patients diagnosed with RA in our hospital from March 2021 to January 2022. The patients with RA met the EULAR/ACR 2010 criteria. We included patients with RA with other rheumatic diseases. A careful allergic history was obtained from patients with RA and physical examination performed.

The first analysis was performed on patient baseline laboratory data at diagnosis of patients with RA with or without sulpha allergy. Sulpha allergy (rash, angioedema and anaphylaxis after drug exposure) was allergy to sulfasalazine or TMP-SMX. The second analysis was performed on seven types of allergic reactions: (1) drug allergies other than sulpha drugs (rash, angioedema and anaphylaxis after drug exposure), (2) food allergy (rash, angioedema and anaphylaxis after foods exposure), (3) allergic contact dermatitis such as metals, and other cosmetics, (4) seasonal allergic rhinitis and/or conjunctivitis (AR and/or AC), and AR and/or AC associated with house dust, (5) asthma, and (6) atopic dermatitis.

Results

There were 513 patients with RA in our study. In the first analysis, 17 patients with sulpha allergy and 496 patients without sulpha drugs were enrolled (Table 1). The median ages (with supha allergy and without sulpha allergy) were 66.0 and 72.0 years old (p=0.40). Females were 82.3% and 77.0%(p=0.4). The median observation period was 97.0 and 69.0 months (p=0.20). Patients with other rheumatic diseases were 11.6 and 6.8% (p=0.34).

Table 1.

Characteristics of RA patients at diagnosis of RA

With sulpha allergy (n = 17)Without sulpha allergy (n = 496)PFemale83.4%76.9%0.77Age, year, y66.0 (56.0-78.5)72.0 (60.0-80.0)0.40Observation period, m97.0 (45.5-182.0)69.0 (31.0-123.8)0.20Patients with other rheumatic diseases11.8%6.8%0.34ANA-positive patients(>1:80)52.9%28.2%0.052Anti-SSA antibody-positive patients46.2%18.2%0.02RF-positive patients40.0%66.8%0.049

The RA patients with sulpha allergy had higher positivity rate of anti-nuclear antibody (ANA) (>1:80) (52.9%, 28.2%: p=0.052), higher positivity rate of anti–Sjögren’s-syndrome-related antigen A autoantibody (anti-SSA antibody) than those without sulpha allergies (46.2%, 18.2%: p = 0.02) and lower positivity rate of rheumatoid factor(RF) than those without sulpha allergies (40.0%, 66.8%: p = 0.049).

In the second analysis drug allergies other than sulpha allergy were more frequent in patients with sulpha allergy. Drug allergies other than sulpha allergy were such as antibiotics and nonsteroidal anti-inflammatory drugs. There were no significant differences in other allergies.

Conclusion

Among patients with RA, patients with sulpha allergy had higher positivity rate of ANA and anti-SSA antibody, and lower positivity rate of RF than those without sulpha allergy. RA patients with sulpha allergy had a higher prevalence of the other drug allergies than those other than sulpha allergy.

References

[1]Konishi MH et al. Allergic diseases in adult-onset Still’s disease and rheumatoid arthtitis. Arerugi. 2021; 70: 965-975.

[2]Konishi MH et al. Allergic Disorders and Drug Allergies in Primary Sjögren’s Syndrome and Rheumatoid Arthritis. EULAR 2021.

Disclosure of Interests

None declared

Patterns of nesting behaviour and nesting success for green turtles at Raine Island, Australia

To understand how turtles use the nesting habitat at Raine Island across a nesting season, and how the turtles respond to the restoration of the island’s dune systems, we identified 534 nesting events for 39 green turtles Chelonia mydas across 2 breeding seasons using data derived from satellite tags. Tracked turtles laid between 4 and 10 clutches of eggs. Patterns of nesting success varied between individuals, within and between seasons. Nesting success was higher in 2018-19 (57%) than 2017-18 (45%), and in both years, nesting success was lowest between October and early January (<50%). In 2017-18, increased rainfall in January corresponded with increased nesting success (>50%). The density of female turtles ashore was lower in 2018-19, and likely explains higher nesting success in 2018-19 because competition for nest space was lower. In 2017-18, females had more attempts per clutch, and the attempts were around 90 min longer. Consequently, energy required to lay a clutch of eggs in 2017-18 was significantly higher than in 2018-19, highlighting potential costs of lower nesting success rates on reproductive output. The area of beach re-profiled as an intervention in 2014 and 2017 was a nesting hotspot in 2017-18. However, in 2018-19, the area was not used to the same extent, and the nesting hotspot occurred on the north-eastern unaltered beach. Collectively, the tracking of turtles across the whole nesting season enabled us to assess overall beach use and nesting site fidelity of green turtles at Raine Island. Results will aid future planning and management of beach restoration activities at turtle nesting sites.

Pebbles and sand on asteroid (162173) Ryugu: In situ observation and particles returned to Earth

The Hayabusa2 spacecraft investigated the C-type (carbonaceous) asteroid (162173) Ryugu. The mission performed two landing operations to collect samples of surface and subsurface material, the latter exposed by an artificial impact. We present images of the second touchdown site, finding that ejecta from the impact crater was present at the sample location. Surface pebbles at both landing sites show morphological variations ranging from rugged to smooth, similar to Ryugu's boulders, and shapes from quasi-spherical to flattened. The samples were returned to Earth on 6 December 2020. We describe the morphology of >5 grams of returned pebbles and sand. Their diverse color, shape, and structure are consistent with the observed materials of Ryugu; we conclude that they are a representative sample of the asteroid.

Microvascular system of hip joint constituents with special reference to ultrastructural findings and early arteriosclerosis

This study aimed to examine the ultrastructure of the arteries of the synovium, acetabular labrum, and ligamentum teres of the hip joint using light, scanning electron, and transmission electron microscopes to identify features of early arteriosclerosis. Tissues collected from three patients (under 40 years of age) with osteonecrosis of the femoral head were immersed in 8 N HCl at 60 °C for 20 min to digest collagen fibers for scanning electron microscopy. Tortuous arterioles and arteries were noted in the joint components, including the synovium, acetabular labrum, and ligamentum teres. The ultrastructure of the arterioles appeared normal; however, intimal thickening was found in most arteries. The thickened intima had abundant elastic fibers and many smooth muscle cells (which were of a synthetic phenotype because they had a few actin filaments and well-developed rough endoplasmic reticulum). This study illustrates that arteriosclerotic changes are present in tortuous arteries in the synovium, acetabular labrum, and ligamentum teres of the hip joint even from a relatively young age and suggests that meandering blood vessels may be the preferred foci of arteriosclerosis.

Detection of fibrotic remodeling of epicardial adipose tissue in patients with atrial fibrillation: Imaging approach based on histological observation

Background

Fibrotic remodeling of epicardial adipose tissue (EAT) is crucial for proinflammatory atrial myocardial fibrosis, which leads to atrial fibrillation (AF).

Objectives

We tested the hypothesis that the ratio of central to marginal adipocyte diameter in EAT represents its fibrotic remodeling. Based on a similar concept, we also tested whether the percent (%) change in EAT fat attenuation determined using computed tomographic (CT) images can detect this remodeling.

Methods

Left atrial appendages were obtained from 76 consecutive AF patients during cardiovascular surgery. EAT in the central area (central EAT: C-EAT) and that adjacent to the atrial myocardium (Marginal EAT: M-EAT) were evaluated histologically. CT images for all of the 76 patients were also analyzed.

Results

The adipocyte diameter was smaller, fibrotic remodeling of EAT (EAT fibrosis) was more severe, and infiltration of macrophages and myofibroblasts was more extensive in M-EAT than in C-EAT. EAT fibrosis was positively correlated with adipocyte diameter in C-EAT and negatively correlated in M-EAT, resulting in a positive correlation between EAT fibrosis and the ratio of central to marginal adipocyte diameter (C/M diameter ratio; r = 0.73, P < .01). The C/M diameter ratio was greater in patients with persistent AF than in those with paroxysmal AF. CT images demonstrated that the %change in EAT fat attenuation was positively correlated with EAT fibrosis.

Conclusion

Our results suggest that the central-to-marginal adipocyte diameter ratio is tightly associated with fibrotic remodeling of EAT. In addition, the %change in EAT fat attenuation determined using CT imaging can detect remodeling noninvasively.

Effect of age and sex on femoral curvature in the Japanese population: three-dimensional computed tomography findings

Age- or sex-related differences in femoral curvature affect the onset of trauma or degenerative diseases of the hip joints. This study aimed to investigate femoral curvature in detail in Japanese individuals using three-dimensional computed tomography, evaluate its effects on the position of proximal femur, and assess differences in femoral curvature according to age and sex. We measured sagittal and coronal femoral bowing in 40 elderly (mean age 85.2 years) and 40 adult (mean age 30.1 years) Japanese individuals using computed tomography. In adult individuals, the radii of the femoral curvatures of the distal end and shaft in the coronal planes were significantly smaller in women than in men. In contrast, no significant difference was observed in femoral curvature between the sexes in the elderly group. Furthermore, the radius of femoral curvature was significantly smaller in elderly individuals than in adult individuals, regardless of the sex and location of the measurement. The highest point of the greater trochanter of the femoral head center was 7.3 ± 5.6 mm in the elderly group and 2.2 ± 4.6 mm in the adult group (p < 0.05). Thus, the femoral curvature varies with age and sex in Japanese individuals. In addition, the femoral curvature could cause positional changes in the proximal femur, such as the highest point of the greater trochanter. Therefore, further studies investigating the biomechanical effects of these morphological changes are warranted.

Early restenosis and late catch-up phenomenon after newer biodegradable- and durable-polymer drug-eluting stent implantations

Background

It is yet to be known whether mechanisms underlying restenosis in newer-generation durable-polymer (DP) and biodegradable-polymer (BP) drug-eluting stents (DES) are different.

Purpose

This study aims to assess the incidences and predictors of early restenosis and late catch-up phenomenon after newer-generation durable-polymer (DP) and biodegradable-polymer (BP) DES.

Methods

Between 2010 and 2017, 13858 lesions in 6350 patients were treated with DES (4393 BP-DES, 9465 DP-DES). The early-term (within 1 year) and late-term (from 1 to 2 years) follow-up angiographies were scheduled. Late catch-up phenomenon was defined as in-stent restenosis (ISR) in lesions that evaded ISR within 1 year after stent implantation. ISR was defined as angiographic restenosis of more than 50%.

Results

The mean patient age was 71 years, and 76.7% were male. Early-term angiographies were performed in 10955 lesions (79.0%). Of those without early-term ISR, late-term angiographies were performed in 7771 lesions (56.1%). The incidences of mid-term restenosis and late catch-up phenomenon were 6.6% and 3.9%, respectively.

In the multivariate regression analyses, history of diabetes, hemodialysis and previous PCI were independent predictors of both early restenosis and late catch-up phenomenon. Also, some lesion characteristics such as chronic total occlusion, right coronary artery ostial lesion, small vessel (defined as reference diameter &lt;2.5mm), long lesion (defined as lesion length &gt;30mm) and treatment of ISR lesion were independent predictors of both early restenosis and late catch-up phenomenon.

Bifurcation lesion and heavily calcified lesion treated with rotablator were independent risk of early restenosis. Bypass graft lesion was an independent predictor of late catch-up phenomenon.

Early restenosis was observed less frequently in DP-DES than in BP-DES (6.3% versus 7.4%, P=0.012). On the contrary, late catch-up phenomenon was observed more frequently in DP-DES than in BP-DES (4.3% versus 2.9%, P=0.026).

Conclusions

Some lesion characteristics were independent predictors of early restenosis and late catch-up phenomenon after newer-generation DES implantation. The deployment of BP-DES resulted in more early restenosis and less late catch-up phenomenon compared to that of DP-DES.

Early Restenosis and Late Catch-Up

Funding Acknowledgement

Type of funding source: None

Clinical features and prognosis of acute myocardial infarction due to coronary artery embolism

Background

Coronary artery embolism (CE) is one of the important causes of acute coronary syndrome (ACS). The feature of CE is that angiographic evidence of coronary artery embolism and thrombosis without atherosclerotic components. However, the prevalence of CE remains unknown because of the diffifulty to diagnose in the acute settings. A recent retrospective analysis suggested that up to 3% of ACS cases may result from CE.

Purpose

The aim of this study was to elucidate the prevalence, clinical features and long-term outcomes including all-cause and cardiac death.

Methods

We analysed the consecutive 2695 patients with first AMI performed coronary intervention between January 2004 and July 2017. CE was diagnosed by clinical histories and angiographic findings. We retrospectively evaluated the clinical and lesion characteristics and outcomes including all-cause and cardiac death.

Results

The prevalence of CE was 2.0% (n=55; CE group and n=2640; non-CE group), including 8 (15%) patients with multivessel CE. The CE group had higher average age (70.8±14.9 vs. 68.4±12.6, p&lt;0.01), prevalence of female (54% vs. 27%, p&lt;0.01), lower prevalence of smoking (34% vs. 62%, p&lt;0.01). The common causes with CE were atrial fibrillation (47%), and malignant tumor (9%), and cardiomyopathy (5%), and patent foramen ovale (4%). Only 20% of patients with CE were treated with anti-coagulant therapy. The rate of distal infarction site (defined as #4, #8, #14–15) was significantly higher in CE group than non-CE group (54.0% vs. 4.9%, p&lt;0.01). During median follow-up of 53.6 [32.6–77.3] months, CE and thromboembolism recurred in 5 patients (CE: 1 patient, stroke 4 patients). The 4-year incidence of all-cause death was significantly higher in the CE group, but cardiac death was not significantly different between the groups (28.8% vs. 14.8%, p=0.03; 12.8% vs. 5.1%, p=0.11).

Conclusion

Compared with non-CE group, the prevalence of distal infarction site was significantly higher in the CE group, and the incidence of cardiac death is not significantly different.

Funding Acknowledgement

Type of funding source: None

Risk stratification based on academic research consortium high bleeding risk criteria for long-term bleeding event after everolimus-eluting stent implantation

Background

Recently, the Academic Research Consortium for High Bleeding Risk (ARC-HBR) criteria has been suggested as the standard definition of HBR.

Purpose

We aimed to investigate the risk stratification based on ARC-HBR Criteria for long-term bleeding event after everolimus-eluting stent implantation

Methods

The study population comprised 1193 patients treated with EES without in-hospital event between 2010 and 2011. Individual ARC-HBR criteria was retrospectively assessed. Major bleeding were defined as the occurrence of a Bleeding Academic Research Consortium type 3 or 5 bleeding event. The mean follow-up period was 2996±433 days.

Results

There were 656 patients (55.0%) in HBR-groups. Cumulative incidence of major bleeding was significantly higher in HBR-group (8.1% vs 3.4% at 4 year, and 16.2% vs 5.7% at 8 year, P&lt;0.001). Cumulative rate of major bleeding tend to be higher as the number of ARC-HBR criteria increased (≥2 Majors: 24.3%, 1 Major: 17.0%, ≥2 Minors:11.7%, and Non-HBR: 5.7%, P&lt;0.001).

Conclusion

ARC-HBR criteria successfully stratified the long-term bleeding risk after drug-eluting stent implantation in real-world practice.

Funding Acknowledgement

Type of funding source: None

Exosc2 deficiency leads to developmental disorders by causing a nucleotide pool imbalance in zebrafish

Exosc2 is one of the components of the exosome complex involved in RNA 3' end processing and degradation of various RNAs. Recently, EXOSC2 mutation has been reported in German families presenting short stature, hearing loss, retinitis pigmentosa, and premature aging. However, the in vivo function of EXOSC2 has been elusive. Herein, we generated Exosc2 knockout (exosc2^-/-) zebrafish that showed larval lethality 13 days post fertilization, with microcephaly, loss of spinal motor neurons, myelin deficiency, and retinitis pigmentosa. Mechanistically, Exosc2 deficiency caused impaired mRNA turnover, resulting in a nucleotide pool imbalance. Rapamycin, which modulated mRNA turnover by inhibiting the mTOR pathway, improved nucleotide pool imbalance in exosc2^-/- zebrafish, resulting in prolonged survival and partial rescue of neuronal defects. Taken together, our findings offer new insights into the disease pathogenesis caused by Exosc2 deficiency, and might help explain fundamental molecular mechanisms in neuronal diseases, such as Alzheimer's disease, amyotrophic lateral sclerosis, and spinal muscular atrophy.

Role of angiopoietin-like protein 2 in atrial fibrosis induced by human epicardial adipose tissue: Analysis using an organo-culture system

BACKGROUND

We have recently reported that peri-left atrial epicardial adipose tissue (EAT) is associated with atrial myocardial fibrosis, in which angiopoietin-like protein 2 (Angptl2) protein content in EAT is associated with atrial myocardial fibrosis.

OBJECTIVE

This study aimed to examine whether Angptl2 contained in peri-left atrial EAT can induce atrial myocardial fibrosis.

METHODS

Human peri-left atrial EAT and abdominal subcutaneous adipose tissue (SAT) were collected from 9 autopsy cases. EAT- or SAT-conditioned medium was dropped onto the rat left atrial epicardial surface using an organo-culture system. Conditioned medium, recombinant Angptl2, and its antibody effects on organo-cultured rat atrial myocardial fibrosis were evaluated. Angptl2 effects on cultured neonatal rat fibroblasts were also investigated.

RESULTS

EAT-conditioned medium induced atrial fibrosis in organo-cultured rat atrium with a progressive increase in the number of myofibroblasts. The profibrotic effect of EAT was greater than that of SAT. EAT in patients with atrial fibrillation induced a more significant atrial fibrosis than in those without. Treatment with human recombinant Angptl2 induced fibrosis in organo-cultured rat atrium, which was suppressed by the concomitant treatment with Angptl2 antibody. In cultured fibroblasts, Angptl2 upregulated the expression of α-smooth muscle actin, transforming growth factor-β1, phospho-extracellular signal-regulated kinase,phospho-inhibitor of κBα, and phospho-p38 mitogen-activated protein kinase.

CONCLUSION

This study demonstrated that Angptl2 contained in EAT played a crucial role in EAT-induced inflammatory atrial fibrosis. The results also suggested that antagonizing the expression of Angptl2 in EAT can be a novel therapeutic approach to prevent atrial fibrillation.

An artificial impact on the asteroid (162173) Ryugu formed a crater in the gravity-dominated regime

The Hayabusa2 spacecraft investigated the small asteroid Ryugu, which has a rubble-pile structure. We describe an impact experiment on Ryugu using Hayabusa2's Small Carry-on Impactor. The impact produced an artificial crater with a diameter >10 meters, which has a semicircular shape, an elevated rim, and a central pit. Images of the impact and resulting ejecta were recorded by the Deployable CAMera 3 for >8 minutes, showing the growth of an ejecta curtain (the outer edge of the ejecta) and deposition of ejecta onto the surface. The ejecta curtain was asymmetric and heterogeneous and it never fully detached from the surface. The crater formed in the gravity-dominated regime; in other words, crater growth was limited by gravity not surface strength. We discuss implications for Ryugu's surface age.

Histological evaluation of the acetabular labrum after bipolar hip hemiarthroplasty: a case report

We report herein the microstructure of the acetabular labrum obtained from a patient with stem loosening but without bipolar cup migration who had undergone hemiarthroplasty for femoral neck fracture 18 years ago. We used light and scanning electron microscopy to investigate the influence of bipolar cup on acetabular labrum in vivo. Deparaffinized blocks were treated with 2 N NaOH to digest the cell matrix, allowing the collagen fibers, constituting the acetabular labrum, to be observed under scanning electron microscopy. Although chondrocyte atrophy was seen, the basic structure was not different from the normal tissue images of the elderly. However, in the deep part of the acetabular labrum, there was an area that was not stained with Alcian blue observed with light microscopy, and there was an amorphous tissue without type II collagen fibrils observed with scanning electron microscopy. These findings proved that the acetabular labrum has partially degenerated over the long term after bipolar hemiarthroplasty, and that the acetabular labrum can survive in vivo in such a condition. Given that hemiarthroplasty has a possibility to preserve the face-to-face tissue in the long term in vivo, it may be one of the valuable options for modern or future joint reconstruction surgery.

P1307 An echocardiographic observation over the disappearing process of the prosthetic valve thrombus caused by the inflammatory hypercoagulability; a case report

Background

Whenever fever and inflammatory reaction continue for a while in the patients with a prosthetic valve, than usual, we must keep infective endocarditis in mind. On the other hand, inflammation and thrombosis are well known to coexist often. There are several reports of thrombotic valves associated with inflammation-activated hypercoagulability. Furthermore, C-reactive protein (CRP) has been reported to imply an increased risk of thrombus especially in the presence of an injury on the prosthetic valve.

Case report

We report a case of a 70-year-old male with a leaflet thrombus on the bioprosthetic aortic valve. He suffered from fever, and symptoms of heart failure and was hospitalized for treatment. Blood tests presented that white blood cell count was 4900/μL (neutrophil 81.1%) and CRP 10.82 mg/dL. Infectious endocarditis (IE) was suspected. Transthoracic echocardiography (TTE) was per-formed, however, vegetation and abscess were not found. Noteworthily, the bioprosthetic valve leaflet on the right coronary cusp showed thickening and opening dysfunction (Figure A, parasternal short axis). Mean pressure gradient (mPG) through the aortic valve was 15mmHg and peak velocity (Vmax) 2.7m/s. Blood culture was negative, and his body temperature and CRP were improved by empirical antibiotic administration. The anticoagulation therapy with warfarin was started, he was discharged from the hospital and followed up in the outpatient clinic. TTE after the initiation of anticoagulation therapy, did not reveal any more dysfunction on the bioprosthetic valve (mPG: 9mmHg, Vmax: 2.2m/s) (Figure B, parasternal short axis). The diagnostic and therapeutic process of this case implied success. The opening-dysfunction of prosthetic valve leaflets was reversible and therefore, we concluded that the thickening of the prosthetic valve could be attributed to thrombus adhesion. Computed Tomography (CT) was not performed because he suffered from chronic kidney disease.

Conclusion

Surely, CT is very useful for the evaluation of thrombotic valves in the patients in whom it is permissible to use contrast agent. However, we could successfully evaluate the recovery process of leaflet thrombosis by echocardiography because of a difficult reason of CT use in this case. The prolongation of inflammatory reaction in the patients with a prosthetic valve should keep IE in mind in everyday life. Even if the findings of bacterial infection are obscure, it is more and more important to observe carefully the change of leaflets, whenever an open-dysfunction and a thrombus adhesion of the prosthetic valves exist.

Abstract P1307 Figure.

P702 An unusual echocardiographic finding of protrusive vegetation caused by perivalvular abscess perforation into the left atrium

Background

It is well-known that Infective endocarditis (IE) caused by S. aureus progresses rapidly and is highly destructive. The most often abscess formation after aortic valve replacement (AVR) is the mitral-aortic intervalvular fibrosa (MAIVF). It is difficult to cure MAIVF radically once infection occurs, and then the abscess tends to spread. After abscess formation is once established, IE tends to be widespread, the prognosis is definitely poor unless surgical repairment is executed, and then an emergency surgery is essential and unavoidable for complete cure. We report an unusual case of aortic valve abscess with perforation of vegetation into the left atrium after aortic valve replacement.

Case report

A 77-year-old man underwent the bioprosthetic AVR for aortic valve stenosis one month ago. On the 9th day after discharge, he visited the hospital for the follow-up. At the time, the body temperature was 36.6 ° C, the blood pressure 133/50 mmHg, white blood cell count 10500/μL, and C-reactive protein 3.31 mg/dL. Transthoracic echocardiography (TTE) demonstrated the perivalvular abscesses on the prosthetic aortic valve and mass structures attached to the MAIVF in the left atrium (Figure A, C). He was hospitalized again and had an emergency re-operation. Intraoperative transesophageal echocardiography (TEE) showed a perivalvular abscess on the prosthetic valve, and a high-intensity structure (vegetation like) protruding from the Valsalva Sinus into the left atrium of the MAIVF (Figure B, D). Surgical findings did not reveal any wart on the native valve itself. One-third of the annulus was disrupted. The subvalvular tissue all around was abscessed. Notably, the abscess cavity between NCC and LCC reached MAIVF of the anterior mitral leaflet, and the structure projecting to the left atrium was vegetation. In this case, TTE pointed out a perivalvular abscess of the aortic valve, IE was suspected at the time of outpatient visit at an early stage after discharge, and the spread of inflammation was observed with a high speed beyond the expectation at the time of operation.

Conclusion

Early after the operation, TTE revealed a mass was protruded into the left atrium. Generally, vegetation is soft and flexible in itself. However, in this case, the vegetation was less mobile, and for that reason, abscesses or tumors were suspected. TEE enabled us to obtain anatomically more detailed information and to foresee the left atrial wall repairment at the time of reoperation. We reported an unusual case of IE with solid vegetation attached to the wall and difficult to diagnose.

Abstract P702 Figure.

P248 Changes of atrial septum defect caused by posture during three-dimensional transesophageal echocardiography ( a case of Platypnea-orthodeoxia syndrome)

Background

Platypnea-Orthodeoxia syndrome (POS) is a rare phenomenon which is characterized postural hypoxia due to the intracardiac shunt from right to left through a patent foramen ovale, an atrial septal defect or a pulmonary arteriovenous malformation. POS is often underestimated because the hypoxia by postural change is difficult to be detected. We evaluated three-dimensional transesophageal echocardiography (TEE) to diagnose POS in an elderly patient.

Case report

A 84-year-old woman suffered from repetitive syncope for several years. She undertook twelve leads electrocardiogram (ECG), screening transthoracic echocardiography (TTE), twenty-four hours ECG and treadmill stress ECG, however, the cause of syncope was not identified. After another syncope event happened, she was transferred to the emergency room. Then, the hypoxia caused by sitting position was pointed out for the first time.

Her hypoxia was improved by supine position and oxygen administration. TTE demonstrated no right heart enlargement. Shunt flow was suspected on her atrial septum; however, it was difficult to reveal it by TTE because of her obesity. Therefore, she underwent intravenous saline injection test. In the decubitus position, an intravenous injection of saline under Valsalva maneuver revealed the shunt flow from the right atrium to the left atrium. Her arterial oxygen saturation (SpO2) was 95%. In the sitting position, a visible shunt flow was observed, then her SpO2 dropped to 85%. By TEE, the shunt hole was found in the oval fossa of the atrial septum. TEE was evaluated by different positions. The atrial defect hole became larger in the sitting position (area 1.05cm2) than in the supine position (area 0.43cm2). As a result, the postural change to sitting revealed Platypnea-Orthodeoxia syndrome associated with ASD. The pulmonary blood flow/systemic blood flow ratio (Qp/Qs) was estimated at 1.6. After surgical ASD closure, she was discharged without any symptoms.

Conclusion

Unclearness of TTE and the absence of a right heart overload may lead to misdiagnosis of POS. If a syncope patient caused hypoxia in the only sitting position, detailed echocardiography should be needed to rule out a diagnosis of POS. This is considerably valuable case of three-dimensional TEE confirmed the changes of ASD size by postural change.

Abstract P248 Figure.

P1472 Concealed thrombus in a 12-year-old boy diagnosed by disappearance of intricate comb-like pectinate muscle form in the left atrial appendage

Background

As previously known, patients with prolonged atrial fibrillation often have atrial thrombus. However, in children, cardiogenic embolism due to atrial fibrillation is rare. Also, the diagnosis of residual thrombus in the left atrial appendage is sometimes difficult even by transesophageal echocardiography (TEE). We have obtained a meaningful comparison between TEE findings and surgical specimen of bilateral atrial appendage.

Case report

A 12-year-old boy admitted to the nearby hospital, because of sudden onset of right-side hemiplegia. Till then, he was born at normal weight and grew up without any problem. The electrocardiogram indicated atrial fibrillation. He was transferred to the pediatric cardiology department of a hospital with higher function for the treatment of cardiogenic thromboembolism.

After 72 hours from the onset of first thromboembolism, a new embolic event happened in his left brachial artery. The contrast-enhanced computed tomography (CT) showed thrombus of bilateral atrium and coronary sinus. Consequently, residual thrombus led to the potential risk of additional embolization. Therefore, catheter cerebral thrombectomy was performed, and then surgical thrombectomy for the bilateral atrium was planned. Preoperative CT showed thrombus in the left atrial appendage (LAA). However, intraoperative TEE showed no obvious thrombus in the LAA. Intricate pectinate muscle formation in the left atrial appendage almost disappeared (figure1A), which suspected remaining thrombus. In addition, massive thrombus was seen in the right atrium and coronary sinus. Coronary sinus thrombus was removed as far as possible, and bilateral atrial appendage resection and myocardial biopsy were performed. Simultaneously, modified-Maze was also done. Heart rhythm returned into sinus rhythm after surgery. Pathological findings did not show specific findings of myocarditis or pericarditis.

Until now, the cause of thrombotic factors has not been fully clarified. Although the time of onset is unknown, probably, heart failure was triggered by atrial fibrillation, and consequently thromboembolism occurred. In the resected left atrial appendage, small thrombus remained among pectinate muscle (figure1B); therefore, postoperative anticoagulation should be needed.

Conclusion

We experienced a boy with thrombus in bilateral atrial appendages. In the resected left atrial appendage, multiple small thrombi remained in the pectinate muscle. From our experience, the disappearance of comb-like form in pectinate muscle by TEE suspects the residual thrombus, especially in the case of cardiogenic embolism.

Abstract P1472 Figure.

P2693Late catch-up phenomenon and late-term target lesion revascularization of two-stenting for coronary bifurcation lesions between first and second generation drug-eluting stents

Background

The second generation drug-eluting stent (G2-DES) has been reported as superior to the first generation drug-eluting stent (G1-DES) in mid-term outcomes. However, the late-term outcomes between G1-DES and G2-DES in two-stenting for coronary bifurcation lesions are not well studied.

Purpose

To evaluate the late catch-up phenomenon and late-term target lesion revascularization (TLR) of two-stenting for coronary bifurcation lesions between G1-DES and G2-DES.

Methods

This study included 1133 lesions in 1089 patients undergoing drug eluting stent implantation with two stenting from 2004 to 2016. These consisted of 496 G1-DES implanted lesions and 637 G2-DES implanted lesions. Late-term follow-up angiography was performed without in-stent restenosis (ISR) and TLR at mid-term follow-up in 582 lesions (242 G1-DES lesions and 340 G2-DES lesions). ISR was defined as more than 50% restenosis. Late catch-up phenomenon was defined as ISR without ISR within 1 year following index stent implantation. Late-term TLR was defined as from 1 to 5 year TLR. Bifurcation lesions were defined as the main branch ranging from the proximal stem to the distal main branch with boundaries defined by 5 mm proximal and distal to the stent-implanted area, and the side branch ranging from the bifurcation carina to the distal side branch with boundaries defined by the carina and 5 mm distal to the stent-implanted area.

Results

The median follow-up duration was 5.1 years (the first and third quarters, 3.2 and 7.1 years). The late-catch up phenomenon rate significantly differed between the G1-DES and G2-DES groups (16.9% vs 8.4%, p=0.001). A significant difference in late catch-up between the same two groups was also observed in bifurcation lesions of the main branch (5.0% vs 0.6%, p=0.001) and side branch (10.3% vs 5.6%, p=0.033), respectively. The 5-year cumulative rates also differed between the two groups in TLR (8.2% vs 3.7% log-rank p=0.001), and late-term TLR (7.0% vs 3.6% log-rank p=0.001).

Conclusion

Two-stenting using G2-DES, compared with G1-DES, significantly reduced late-term restenosis and TLR. The restenosis rate in bifurcation area may be associated with differences between two groups in late-term outcome.

P5614The association between tissue morphology assessed with optical coherence tomography and mid and late-term results after percutaneous coronary intervention for in-stent restenosis lesions

Background

It was reported that tissue morphology of in-stent restenosis (ISR) lesions assessed with optical coherence tomography (OCT) had an effect on midterm results including ISR and target lesion revascularization (TLR) rates after percutaneous coronary intervention (PCI). However, little was known about the association between tissue morphology assessed with OCT and late-term results.

Methods

We performed PCI treated with paclitaxel coated balloon (PCB) or drug-eluting stent (DES) for 452 ISR lesions (260 lesions with fibrous plaque and 192 lesions with lipid-laden plaque) using OCT between May 2008 and July 2016. Six- to eight-month (midterm) angiographic follow-up was performed on 422 of the 452 ISR lesions (follow-up rate: 93.4%). Furthermore, eighteen- to twenty-month (late-term) angiographic follow-up was performed on 337 of the 361 ISR lesions (follow-up rate: 93.4%) which were free from midterm TLR. We examined the association between tissue morphology, midterm-results and late-term results including ISR and TLR rates. Fibrous plaque was defined as homogeneous, signal-rich regions with low attenuation. Lipid-laden plaque was defined as diffuse border, signal poor regions with high attenuation.

Results

The patients were 353 men and 69 women, and the mean age was 68.8±9.6 years. PCI were performed with PCB in 285 lesions (PCB group) and DES in 137 lesions (DES group). The figure shows the angiographic midterm results of the 422 lesions and late-term results of the 337 lesions with respect to each tissue morphology and each PCI device. There was no difference in ISR and TLR rates of lesions with both fibrous and lipid-laden plaque at midterm between the two groups. ISR and TLR rates of lesions with lipid-laden plaque at late-term were significantly higher in the PCB group than in the DES group, while there was no difference in ISR and TLR rates of lesions with fibrous plaque at late-term between two groups.

Figure 1

Conclusion

Tissue morphology of ISR lesions might have an impact on outcomes after PCI. Morphological assessment of ISR tissue using OCT might suggest favorable types of PCI for ISR lesions.

P1628Angiopoietin-like protein (Angptl) 2 secreted from epicardial adipose tissue induces atrial myocardial fibrosis

Background

Using excised human left atrial appendage samples, we previously demonstrated that epicardial adipose tissue (EAT) are highly associated with atrial myocardial fibrosis as a substrate of atrial fibrillation (AF). We also reported the relationship between Angptl2 in EAT and atrial fibrosis. However, the mechanism is not clear. The purpose is to clarify the mechanisms underlying the effect of EAT on the atrial myocardium.

Methods

Human peri-left atrial EAT and abdominal subcutaneous adipose tissue (SAT) samples were obtained from 6 cases (2 females, 70.2±13.2 years). 50 mg of EAT and SAT were quickly washed with PBS and centrifuged 1min at 1200rpm. After 3 times this procedures, adipose tissues were cultured in DMEM F12 medium with Fetal bovine Serum (FBS) overnight.

After pre-incubation, EAT and SAT tissues were washed and centrifuge d three times and cultured in medium without FBS for 24hours. Finally, we collected oozed medium (conditioned medium) and used for experiments.

Concentrations of Angptl2 in conditioned medium were measured by ELISA.

To study the effects of conditioned medium, we used “organo-culture” system. Isolated atrium from 8week old male Sprague-Dawley rats were placed on the porous membrane with the endothelial face toward the membrane. After that, loading medium (conditioned medium:culture medium = 1:4), culture medium (control), or recombinant Angptl2 were dropped onto the epicardial face of the atrium once a day and incubated for 7 days (37°C, 5% CO2).

Then, histological and immunohistochemical analysis were performed. We also performed quantitative reverse transcription–polymerase chain reaction (RT–PCR) analysis.

Next, we isolated and cultured neonatal rat fibroblast and loaded Angptl2 for 24 hours.After collected these cells, we performed western blotting analysis.

Results

Atria organo-culture incubated for 7 days with conditioned medium showed global fibrosis. At epicardial side, fibrotic area of EAT group was significantly greater compared to that of SAT and control group (P<0.05).

mRNA of Col1a1, col3a1 and TGFβ1 were significantly increased in EAT group compared with the SAT and control group.

And, the concentration of conditioned medium created from EAT was significant higher than that from SAT (P<0.05).

Then, we dropped 500 ng/ml of recombinant Angptl2 onto the rat atria. Fibrotic area of Angptl22 group significantly greater than that of control with increasing number of α-SMA positive cells, and mRNA of col3a1 and TGFβ1 were significantly increased in Angptl2 group compared with control group.

In cultured fibroblasts, α-SMA and p-ERK expression were increased in Angptl2 group measured by western blotting analysis.

Conclusions

Our results demonstrated that EAT rather than SAT induces atrial myocardial fibrosis. There is a possibility that Angptl2 effused from EAT plays a part in atrial fibrosis thought EAT paracrine effect.

Acknowledgement/Funding

ONO PHARMACEUTICAL CO

Ultrastructure and three-dimensional architecture of the anterior cruciate ligament in the knee joints of young and old monkeys

We examined the ultrastructure of the anterior cruciate ligament and assessed age-related changes by comparing the ligaments of young and old monkeys. Ultrathin sections of the anterior cruciate ligament were observed by transmission electron microscopy. The three-dimensional architecture of collagen fibers in the ligament was examined by scanning electron microscopy after tissue specimens were treated with 2 N NaOH to digest the extracellular matrix. At the surface layer of the cruciate ligament in young monkeys, fusiform-shaped fibroblasts actively produced collagen fibrils. The ligament consisted of parallel bundles of dense collagen fibrils of approximately 200 nm in diameter. Collagen fibrils appeared to run linearly. Ligament fibrocytes in the deep layer had a stellate form. Ligament fibrocytes decreased in number and showed marked atrophy in old age. Collagen fibrils had a looser configuration in older monkeys. Despite atrophy of fibroblasts in the deep layer of the anterior cruciate ligament, the area with atrophic fibroblasts in the ligament expands with age, which can likely cause deterioration of and a reduction in collagen fibers. This information can be applied in studies on the cause of the low repair ability of and aging-related changes in the anterior cruciate ligament in humans.

Hayabusa2 arrives at the carbonaceous asteroid 162173 Ryugu-A spinning top-shaped rubble pile

The Hayabusa2 spacecraft arrived at the near-Earth carbonaceous asteroid 162173 Ryugu in 2018. We present Hayabusa2 observations of Ryugu's shape, mass, and geomorphology. Ryugu has an oblate "spinning top" shape, with a prominent circular equatorial ridge. Its bulk density, 1.19 ± 0.02 grams per cubic centimeter, indicates a high-porosity (>50%) interior. Large surface boulders suggest a rubble-pile structure. Surface slope analysis shows Ryugu's shape may have been produced from having once spun at twice the current rate. Coupled with the observed global material homogeneity, this suggests that Ryugu was reshaped by centrifugally induced deformation during a period of rapid rotation. From these remote-sensing investigations, we identified a suitable sample collection site on the equatorial ridge.

The geomorphology, color, and thermal properties of Ryugu: Implications for parent-body processes

The near-Earth carbonaceous asteroid 162173 Ryugu is thought to have been produced from a parent body that contained water ice and organic molecules. The Hayabusa2 spacecraft has obtained global multicolor images of Ryugu. Geomorphological features present include a circum-equatorial ridge, east-west dichotomy, high boulder abundances across the entire surface, and impact craters. Age estimates from the craters indicate a resurfacing age of [Formula: see text] years for the top 1-meter layer. Ryugu is among the darkest known bodies in the Solar System. The high abundance and spectral properties of boulders are consistent with moderately dehydrated materials, analogous to thermally metamorphosed meteorites found on Earth. The general uniformity in color across Ryugu's surface supports partial dehydration due to internal heating of the asteroid's parent body.

A Case of Feline T-cell Lymphoma with Tropism for Striated Muscle and Peripheral Nerve

An 11-year-old female American shorthair cat was presented with a 3-month history of hindlimb ataxia and knuckling of the left forelimb. Clinical abnormalities included weight loss, hyperaesthesia of the neck and back, cardiac murmur and systemic muscle atrophy. The cat died 10 days after the initial presentation and a necropsy examination was performed. Grossly, extensive pale lesions were seen in the wall of the left ventricle and the septum of the heart. There were no detectable masses in the heart, skeletal muscles or peripheral nerves. Histopathological examination revealed diffuse, extensive infiltration of atypical lymphoid cells in the heart; the cardiac muscles were markedly degenerate and atrophic and were replaced by the neoplastic cells. Neoplastic cells with similar morphology were seen in all specimens of the skeletal muscles and peripheral nerves. Clonality analysis of the paraffin wax-embedded heart tissue revealed a monoclonal rearrangement of the gene encoding the T-cell receptor γ chain. Based on these findings, the case was diagnosed as T-cell lymphoma with tropism for striated muscle and peripheral nerve.

Three-dimensional architecture of the ligamentum teres in the human hip joint

Background

We aimed to investigate the three-dimensional structure of the collagenous fibers of the ligamentum teres (LT) of the human hip and clarify the LT micro-anatomy at the attachment of the femoral head.

Methods

Femoral heads and LT were collected during hip arthroplasty. Specimens were cut into 5-10-mm squares, prepared, developed, and observed under a light microscope. Next, specimens were prepared and examined under a scanning electron microscope (SEM).

Results

Under optical microscope, LT adhered to the artificial cartilage at the attachment of the femoral head. Under SEM, LT comprised parallelly arranged collagenous fibers and the fine collagenous fibrils were twisted. While the central collagenous fibers of the LT at the attachment of the femoral head penetrated the articular cartilage tissue and reached the ring-shaped bone, fibers at the margin traversed and adhered to the cartilage surface.

Conclusion

Articular cartilage and subchondral bone are present at the LT attachment to the femoral head. Although collagenous fibers of the LT show parallel arrangement at the main trunk, they are dispersed at the cartilage surface and not all reach the thin subchondral bone of the femoral head. This could possibly weaken ligament strength at the attachment of the femoral head.

Level of evidence

IV.

Strength and Viscosity Effects on Perturbed Shock Front Stability in Metals

Computational modeling and experimental measurements on metal samples subject to a laser-driven, ablative Richtmyer-Meshkov instability showed differences between viscosity and strength effects. In particular, numerical and analytical solutions, coupled with measurements of fed-through perturbations, generated by perturbed shock fronts onto initially flat surfaces, show promise as a validation method for models of deviatoric response in the postshocked material. Analysis shows that measurements of shock perturbation amplitudes at low sample thickness-to-wavelength ratios are not enough to differentiate between strength and viscosity effects, but that surface displacement data of the fed-through perturbations appears to resolve the ambiguity. Additionally, analytical and numerical results show shock front perturbation evolution dependence on initial perturbation amplitude and wavelength is significantly different in viscous and materials with strength, suggesting simple experimental geometry changes should provide data supporting one model or the other.