Preparation of large biological samples for high-resolution, hierarchical, synchrotron phase-contrast tomography with multimodal imaging compatibility.

Imaging across different scales is essential for understanding healthy organ morphology and pathophysiological changes. The macro- and microscale three-dimensional morphology of large samples, including intact human organs, is possible with X-ray microtomography (using laboratory or synchrotron sources). Preparation of large samples for high-resolution imaging, however, is challenging due to limitations such as sample shrinkage, insufficient contrast, movement of the sample and bubble formation during mounting or scanning. Here, we describe the preparation, stabilization, dehydration and mounting of large soft-tissue samples for X-ray microtomography. We detail the protocol applied to whole human organs and hierarchical phase-contrast tomography at the European Synchrotron Radiation Facility, yet it is applicable to a range of biological samples, including complete organisms. The protocol enhances the contrast when using X-ray imaging, while preventing sample motion during the scan, even with different sample orientations. Bubbles trapped during mounting and those formed during scanning (in the case of synchrotron X-ray imaging) are mitigated by multiple degassing steps. The sample preparation is also compatible with magnetic resonance imaging, computed tomography and histological observation. The sample preparation and mounting require 24-36 d for a large organ such as a whole human brain or heart. The preparation time varies depending on the composition, size and fragility of the tissue. Use of the protocol enables scanning of intact organs with a diameter of 150 mm with a local voxel size of 1 µm. The protocol requires users with expertise in handling human or animal organs, laboratory operation and X-ray imaging.

Imaging intact human organs with local resolution of cellular structures using hierarchical phase-contrast tomography.

Imaging intact human organs from the organ to the cellular scale in three dimensions is a goal of biomedical imaging. To meet this challenge, we developed hierarchical phase-contrast tomography (HiP-CT), an X-ray phase propagation technique using the European Synchrotron Radiation Facility (ESRF)'s Extremely Brilliant Source (EBS). The spatial coherence of the ESRF-EBS combined with our beamline equipment, sample preparation and scanning developments enabled us to perform non-destructive, three-dimensional (3D) scans with hierarchically increasing resolution at any location in whole human organs. We applied HiP-CT to image five intact human organ types: brain, lung, heart, kidney and spleen. HiP-CT provided a structural overview of each whole organ followed by multiple higher-resolution volumes of interest, capturing organotypic functional units and certain individual specialized cells within intact human organs. We demonstrate the potential applications of HiP-CT through quantification and morphometry of glomeruli in an intact human kidney and identification of regional changes in the tissue architecture in a lung from a deceased donor with coronavirus disease 2019 (COVID-19).

Photon-counting detectors in computed tomography: from quantum physics to clinical practice.

Over the last decade, a fundamentally new type of computed tomography (CT) detectors has proved its superior capabilities in both physical and preclinical evaluations and is now approaching the stage of clinical practice. These detectors are able to discriminate single photons and quantify their energy and are hence called photon-counting detectors. Among the promising benefits of this technology are improved radiation dose efficiency, increased contrast-to-noise ratio, reduced metal artifacts, improved spatial resolution, simultaneous multi-energy acquisitions, and the prospect of multi-phase imaging within a single acquisition using multiple contrast agents. Taking the conventional energy-integrating detectors as a reference, the authors demonstrate the technical principles of this new technology and provide phantom and patient images acquired by a whole-body photon-counting CT. These images serve as a basis for discussing the potential future of clinical CT.

[Microvascular changes in COVID-19]. / Mikrovaskuläre Veränderungen bei COVID-19.

BACKGROUND: Clinically, coronavirus disease 2019 (COVID-19) is associated with a wide range of symptoms, which can range from mild complaints of an upper respiratory infection to life-threatening hypoxic respiratory insufficiency and multiorgan failure. OBJECTIVE: The initially identified pulmonary damage patterns, such as diffuse alveolar damage in acute lung failure, are accompanied by new findings that draw a more complex scenario. These include microvascular involvement and a wide range of associated pathologies of multiple organ systems. A back-scaling of microstructural vascular changes is possible via targeted correlation of pathological autopsy results with radiological imaging. MATERIAL AND METHODS: Radiological and pathological correlation as well as microradiological imaging to investigate microvascular involvement in fatal COVID-19. RESULTS: The cases of two COVID-19 patients are presented. Patient 1 showed a relative hypoperfusion in lung regions that did not have typical COVID-19 infiltrates; the targeted post-mortem correlation also showed subtle signs of microvascular damage even in these lung sections. Patient 2 showed both radiologically and pathologically advanced typical COVID-19 destruction of lung structures and the case illustrates the damage patterns of the blood-air barrier. The perfusion deficit of the intestinal wall shown in computed tomography of patient 2 could not ultimately clearly be microscopically attributed to intestinal microvascular damage. CONCLUSION: In addition to microvascular thrombosis, our results indicate a functional pulmonary vasodysregulation as part of the pathophysiology during the vascular phase of COVID-19. The clinical relevance of autopsies and the integration of radiological imaging findings into histopathological injury patterns must be emphasized for a better understanding of COVID-19.

Dephasing and diffusion on the alveolar surface.

We propose a surface model of spin dephasing in lung tissue that includes both susceptibility and diffusion effects to provide a closed-form solution of the Bloch-Torrey equation on the alveolar surface. The nonlocal susceptibility effects of the model are validated against numerical simulations of spin dephasing in a realistic lung tissue geometry acquired from synchotron-based µCT data sets of mouse lung tissue, and against simulations in the well-known Wigner-Seitz model geometry. The free induction decay is obtained in dependence on microscopic tissue parameters and agrees very well with in vivo lung measurements at 1.5 Tesla to allow a quantification of the local mean alveolar radius. Our results are therefore potentially relevant for the clinical diagnosis and therapy of pulmonary diseases.

Evolution of insular Pacific Pittosporum (Pittosporaceae): origin of the Hawaiian radiation.

We investigated the origin of Hawaiian Pittosporum and their relationship to other South Pacific Pittosporum species using internal transcribed spacer sequences of nuclear ribosomal DNA. We performed both maximum-parsimony and maximum-likelihood analyses, which produced congruent results. Sequence divergence was 0.0% between Hawaiian members of Pittosporum. These taxa formed a strongly supported clade, suggesting a single colonization event followed by phyletic radiation. Sister to the Hawaiian clade were two South Pacific species, P. yunckeri from Tonga and P. rhytidocarpum from Fiji. This result presents convincing evidence for a South Pacific origin of Hawaiian Pittosporum. Our results also identify a monophyletic group comprising three species representing the Fijian Province and East Polynesia, two introductions onto New Caledonia, and at least one (but possibly two) introduction(s) onto New Zealand. Whether the New Zealand taxa form a monophyletic group is unclear from these data. Previous morphologically based hypotheses, however, suggest the presence of four different lineages occupying New Zealand. The nonmonophyly of the New Caledonian species was not surprising based on the extent of their morphological diversity. Although this latter result is not strongly supported, these species are morphologically complex and are currently the subject of taxonomic revision and molecular systematic analyses.

A unique Hawaiian Schiedea (caryophyllaceae: Alsinoideae) with only five fertile stamens.

The floral organogenesis and subsequent ontogenies of the Hawaiian endemic species Schiedea pubescens from Maui, Moloka'i, and Lana'i, and the Wai'anae Mountains, O'ahu, populations previously considered to be varietally distinct, were examined using the scanning electron microscope (SEM). The O'ahu population consistently produced only five fertile stamens, those of the inner whorl. The five stamens of the alternisepalous or outer whorl abort prior to microsporogenesis and fail to elongate. Additional vegetative differences between the two taxa, combined with the floral morphology characters, merit the description of the O'ahu population as a new species, S. pentandra, described herein.

Pharmacokinetic and pharmacodynamic properties of ramipril in patients with congestive heart failure (NYHA III-IV).

To investigate the pharmacokinetics and pharmacodynamics of a new angiotensin converting enzyme (ACE) inhibitor, ramipril (HOE 498), in patients with cardiac insufficiency (NYHA III-IV), we performed an open trial with a follow-up of 10 days. Twenty-seven patients (18 females, 9 males), mean aged 62 years (46-83) with severe heart failure, were included. After a single oral dose of 5 mg ramipril, the plasma and urine levels of ramipril, ramiprilat, ACE plasma activity, standard laboratory values, blood pressure and pulse rate were evaluated. The maximal plasma level of ramipril was 57.0 +/- 26.8 ng/ml after 1.4 h; t1/2 was 2.4 +/- 1.2 h. The peak level of ramiprilat was 27.9 +/- 24 ng/ml after 4.6 h; t1/2 for the active compound was 6 +/- 4.2 h. The total recovery of ramipril and metabolites in urine was on average 39 +/- 17.5% within 96 h. Ninety-five percent inhibition of ACE activity was observed in all patients and 80% inhibition lasted 24 h. Systolic and diastolic blood pressure decreased without changes in heart rate. Five patients had mild side effects: hypotension, diarrhea, and dizziness. In conclusion, in patients with severe heart failure, plasma levels of drug and active metabolite were higher and remained measurable longer, with more sustained inhibition of ACE activity than reported in healthy volunteers. This indicates that titration should start with lower doses (1.25-2.5 mg) and that doses above 5 mg may rarely be necessary.

[Noninvasive diagnosis of bilocular left atrial and right ventricular myxoma of the heart]. / Nichtinvasive Diagnostik eines bilokulären linksatrialen und rechtsventrikulären Myxoms des Herzens.

Bilateral cardiac myxomas are very rare and therefore mostly overlooked. In most cases the diagnosis has been made intraoperatively or at postmortem examination. We report on a 60-year-old woman with a left atrial and right ventricular myxoma where diagnosis was made by echocardiography and computer tomography, and confirmed histologically after successful surgical and therapeutic aspects are discussed.

[Therapy refractory sinus tachycardia following polytrauma]. / Therapierefraktäre Sinustachykardie nach Polytrauma.

The course of a 20-year-old patient with head injury and fractures of the ribs is reported, in whom sinus tachycardia has now persisted for three years. Antiarrhythmic treatment with calcium antagonists, beta-blocking agents and digitalis did not reduce the rate of the tachycardia. Contusio cordis, as well as different mechanisms of arrhythmias after cerebral trauma are discussed.

[Combination of sotalol with the class I B substances mexiletine or tocainide in complex ventricular extrasystole]. / Kombination von Sotalol mit den Klasse-I-B-Substanzen Mexiletin oder Tocainid bei komplexer ventrikulärer Extrasystolie.

In 34 patients with ventricular tachyarrhythmias the effect of the antiarrhythmic therapy of sotalol (160-320 mg p.o.) in combination with the type-I-B-agent mexiletine (600-800 mg p.o.) or tocainide (800-1200 mg p.o.) was studied by Holter monitoring. In all patients 2.2 +/- 1.1 drugs trials had failed, including amiodarone in 8 patients and beta blocking substances in 15 patients. The combination of sotalol with mexiletine or tocainide reduced ventricular ectopic beats by 79% and complex ventricular arrhythmias (pairs and salvoes) by 85%. A significant reduction of ventricular ectopic beats (greater than 80%) was reached in 74% of the patients, of pairs and salvoes (greater than 90%) in 79%. There was no difference in the antiarrhythmic efficacy between the combination of sotalol/mexiletine and sotalol/tocainide. Intervals of the resting ECG or laboratory values did not change significantly. In 5 patients with sotalol/tocainide and 1 patient with sotalol/mexiletine, side effects were observed which necessitated discontinuation of the treatment. The results show that sotalol, in combination with mexiletine or tocainide, has a potent antiarrhythmic effect in patients with otherwise drug-refractory ventricular arrhythmias.

[Cyanotic patient with right ventricular dilatation and ventricular arrhythmias]. / Zyanotische Patientin mit rechtsventrikulärer Dilatation und ventrikulären Herzrhythmusstörungen.

Uhl's disease is a very rare congenital anomaly of the heart. Extreme dilatation of the right ventricle is accompanied by virtual absence of the right ventricular myocardium. We report on a 30-year-old woman with ventricular arrhythmias and atrial-septal defect where the diagnosis was made by echocardiography and confirmed by angiocardiography. Diagnostic and therapeutic possibilities are discussed.

Current concepts in the treatment of cardiac arrhythmias.

Attention has been paid to the recognition of patients at risk of sudden cardiac death. Whereas the long-term prognosis of healthy subjects with frequent and complex ventricular premature complexes is similar to that of the normal population, coronary patients with frequent and complex ectopy are at high risk of sudden cardiac death; in this group, recent myocardial infarction and impaired left ventricular function increase the likelihood for sudden death. In a similar way, patients with idiopathic dilated cardiomyopathy and reduced left ventricular function, in whom frequent episodes of ventricular tachycardias or ventricular pairs are detected, are at high risk of sudden death. These patient groups with left ventricular impairment may potentially be treated with the alpha 1-antagonist indoramin, which has exhibited antiarrhythmic properties in animal experiments. In a therapeutic dose, indoramin prohibited reflex tachycardia but did not show any additional electrophysiologic effects. Therefore, no adverse effects on sinus node function or on atrioventricular conduction, or intraventricular conduction must be expected during therapy with indoramin.

[Effects of prostacyclin (PGI2) on tachycardic heart arrhythmias following aortocoronary venous bypass operations]. / Einfluss von Prostacyclin (PGI2) auf tachykarde Herzrhythmusstörungen nach aortokoronaren Venen-Bypass-Operationen.

In a prospective double-blind study of 40 male patients requiring aorto-coronary bypass surgery, a dose of 8 ng/kg/min of PGI2 was infused throughout extracorporeal circulation (ECC) (control group: glycine buffer). Between the two treatment groups there was no difference in preoperative hemodynamic parameters, number of preoperative infarctions, or number of implantated aorto-coronary vein grafts. Before, during and up to one day after ECC, extensive hemodynamic and hemostaseologic examinations were performed repeatedly (a total of twelve times in each patient). During ECC and due to inhibition of platelet function, platelet counts were significantly higher in the PGI2-treated group without clinical evidence for an increased bleeding tendency. Systemic blood pressure, heart rate and perfusion pressure did not differ significantly in the two treatment groups (with the exception of one control 60 minutes after onset of ECC). Peri- and postoperative function of the kidneys and lung also demonstrated similar results in both treatment groups. The platelet preserving effect of PGI2 correlated with a significant decrease of severe arrhythmias (tachyarrhythmias before termination of extracorporeal circulation) and a reduction in mechanical reperfusion. It is suggested that PGI2 exerts its beneficial effect on the myocardium by inhibiting platelet aggregation and/or by an antiarrhythmic effect on the myocardium. Whether the antiarrhythmic effect of PGI2 on the myocardium is indirect (reduction of microcirculatory disorders produced by inhibition of platelet aggregation) or direct (electrical stabilization of the myocardial cell membrane), is the subject of further investigations.