Intravital Dynamic and Correlative Imaging of Mouse Livers Reveals Diffusion-Dominated Canalicular and Flow-Augmented Ductular Bile Flux

BACKGROUND AND AIMS

Small-molecule flux in tissue microdomains is essential for organ function, but knowledge of this process is scant due to the lack of suitable methods. We developed two independent techniques that allow the quantification of advection (flow) and diffusion in individual bile canaliculi and in interlobular bile ducts of intact livers in living mice, namely fluorescence loss after photoactivation and intravital arbitrary region image correlation spectroscopy.

APPROACH AND RESULTS

The results challenge the prevailing "mechano-osmotic" theory of canalicular bile flow. After active transport across hepatocyte membranes, bile acids are transported in the canaliculi primarily by diffusion. Only in the interlobular ducts is diffusion augmented by regulatable advection. Photoactivation of fluorescein bis-(5-carboxymethoxy-2-nitrobenzyl)-ether in entire lobules demonstrated the establishment of diffusive gradients in the bile canalicular network and the sink function of interlobular ducts. In contrast to the bile canalicular network, vectorial transport was detected and quantified in the mesh of interlobular bile ducts.

CONCLUSIONS

The liver consists of a diffusion-dominated canalicular domain, where hepatocytes secrete small molecules and generate a concentration gradient and a flow-augmented ductular domain, where regulated water influx creates unidirectional advection that augments the diffusive flux.

The pyrrolizidine alkaloid senecionine induces CYP-dependent destruction of sinusoidal endothelial cells and cholestasis in mice

Pyrrolizidine alkaloids (PAs) are widely occurring phytotoxins which can induce severe liver damage in humans and other mammalian species by mechanisms that are not fully understood. Therefore, we investigated the development of PA hepatotoxicity in vivo, using an acutely toxic dose of the PA senecionine in mice, in combination with intravital two-photon microscopy, histology, clinical chemistry, and in vitro experiments with primary mouse hepatocytes and liver sinusoidal endothelial cells (LSECs). We observed pericentral LSEC necrosis together with elevated sinusoidal marker proteins in the serum of senecionine-treated mice and increased sinusoidal platelet aggregation in the damaged tissue regions. In vitro experiments showed no cytotoxicity to freshly isolated LSECs up to 500 µM senecionine. However, metabolic activation of senecionine by preincubation with primary mouse hepatocytes increased the cytotoxicity to cultivated LSECs with an EC50 of approximately 22 µM. The cytochrome P450 (CYP)-dependency of senecionine bioactivation was confirmed in CYP reductase-deficient mice where no PA-induced hepatotoxicity was observed. Therefore, toxic metabolites of senecionine are generated by hepatic CYPs, and may be partially released from hepatocytes leading to destruction of LSECs in the pericentral region of the liver lobules. Analysis of hepatic bile salt transport by intravital two-photon imaging revealed a delayed uptake of a fluorescent bile salt analogue from the hepatic sinusoids into hepatocytes and delayed elimination. This was accompanied by transcriptional deregulation of hepatic bile salt transporters like Abcb11 or Abcc1. In conclusion, senecionine destroys LSECs although the toxic metabolite is formed in a CYP-dependent manner in the adjacent pericentral hepatocytes.

Bile Microinfarcts in Cholestasis Are Initiated by Rupture of the Apical Hepatocyte Membrane and Cause Shunting of Bile to Sinusoidal Blood

Bile duct ligation (BDL) is an experimental procedure that mimics obstructive cholestatic disease. One of the early consequences of BDL in rodents is the appearance of so-called bile infarcts that correspond to Charcot-Gombault necrosis in human cholestasis. The mechanisms causing bile infarcts and their pathophysiological relevance are unclear. Therefore, intravital two photon-based imaging of BDL mice was performed with fluorescent bile salts (BS) and non-BS organic anion analogues. Key findings were followed up by matrix-assisted laser desorption ionization imaging, clinical chemistry, immunostaining, and gene expression analyses. In the acute phase, 1-3 days after BDL, BS concentrations in bile increased and single-cell bile microinfarcts occurred in dispersed hepatocytes throughout the liver caused by the rupture of the apical hepatocyte membrane. This rupture occurred after loss of mitochondrial membrane potential, followed by entry of bile, cell death, and a "domino effect" of further death events of neighboring hepatocytes. Bile infarcts provided a trans-epithelial shunt between bile canaliculi and sinusoids by which bile constituents leaked into blood. In the chronic phase, ≥21 days after BDL, uptake of BS tracers at the sinusoidal hepatocyte membrane was reduced. This contributes to elevated concentrations of BS in blood and decreased concentrations in the biliary tract. Conclusion: Bile microinfarcts occur in the acute phase after BDL in a limited number of dispersed hepatocytes followed by larger infarcts involving neighboring hepatocytes, and they allow leakage of bile from the BS-overloaded biliary tract into blood, thereby protecting the liver from BS toxicity; in the chronic phase after BDL, reduced sinusoidal BS uptake is a dominant protective factor, and the kidney contributes to the elimination of BS until cholemic nephropathy sets in.

TB and MDR/XDR-TB in European Union and European Economic Area countries: managed or mismanaged?

In spite of the growing awareness of emerging drug-resistant Mycobacterium tuberculosis, the extent of inappropriate tuberculosis (TB) case management may be underestimated, even in Europe. We evaluated TB case management in the European Union/European Economic Area countries, with special focus on multidrug-resistant (MDR) and extensively drug-resistant (XDR)-TB, using a purposely developed, standardised survey tool. National reference centres in five countries representing different geographical, socioeconomic and epidemiological patterns of TB in Europe were surveyed. 40 consecutive, original clinical TB case records (30 MDR/XDR-TB cases) were reviewed in each of the five countries. The findings were recorded and, through the survey tool, compared with previously agreed and identified international standards. Deviations from international standards of TB care were observed in the following areas: surveillance (no information available on patient outcomes); infection control (lack of respiratory isolation rooms/procedures and negative-pressure ventilation rooms); clinical management of TB, MDR-TB and HIV co-infection (inadequate bacteriological diagnosis, regimen selection and treatment duration); laboratory support; and diagnostic/treatment algorithms. Gaps between present international standards of care and the management of MDR/XDR-TB patients were identified. Training, increased awareness, promotion of standards and allocation of appropriate resources are necessary to ensure appropriate care and management as well as to prevent further emergence of drug resistance.

Cerebral venous thrombosis: a diagnostic and treatment update

INTRODUCTION

Cerebral venous thrombosis (CVT) is still a significant diagnostic and therapeutic challenge, due to its high variability of clinical manifestations and its lack of a clear therapeutic consensus.

SOURCES

A search of the medical literature was made through PubMed using the conjoined terms of CVT and epidemiology (428 results), pathophysiology (504 results), aetiology (2714 results), diagnosis (2802 results), treatment (2173 results) and outcome (648 results). Original and review publications deemed to be useful for this review were selected. Classical and historical works on CVT were also included.

DEVELOPMENT

The present paper reviews the fundamental aspects of the epidemiology, pathophysiology and aetiology of CVT. There is a comparison of the most common initial clinical manifestations along with a description of the most important neuroradiological studies needed to establish a diagnosis, all based on multiple published series. Moreover, in order to serve as an important tool in both clinical practice and continuing research, there is also an analysis of recent evidence on treatment and prognosis.

CONCLUSIONS

CVT represents approximately 0.5% of all stroke cases worldwide. Headache, focal deficits and seizures are the most frequent initial clinical manifestations, representing 89%, 50%, and 35% of appearances, respectively. Magnetic resonance imaging (MRI) in combination with magnetic resonance venography has proved to have the highest sensitivity and specificity in establishing a diagnosis. An equal alternative to MRI is computed tomography venography due to similar diagnostic results. Pharmacological treatment with heparin is widely accepted today. Recurrence and mortality rates of CVT are 2.8 per 100 cases and 10%, respectively, despite of anticoagulation treatment.

[Pulmonary bleeding after lung transplantation]

BACKGROUND

Bronchial arteries are not anastomosed during lung transplantation. We analyzed the occurrence of pulmonary hemorrhage after transplantation.

PATIENTS AND METHODS

235 patients were included.

RESULTS

We observed pulmonary bleeding in 4/235 patients (1.7 %). All four cases were due to transplant-specific disorders (arrosion of pulmonary artery in three cases, coagulopathy in one patient).

CONCLUSIONS

The analysis shows, that usual pulmonary hemorrhage does not occur in lung transplant recipients. This underlines the role of bronchial arteries in pulmonary hemorrhage of non-LTX-patients.

[Morphological variability of synovial sarcoma in childhood]

We report on an unusual locally recurrent plantar soft tissue sarcoma in a 7-years-old boy. Due to an unusual morphology a clear diagnosis was initially not possible. The histologically different recurrent tumor was classified as synovial sarcoma by means of immunohistochemistry, ultrastructural and molecular analysis. This case demonstrates the variable morphological appearance of synovial sarcoma and the value of modern diagnostic procedures in such circumstances.

Psychological and academic functioning in college students with attention deficit hyperactivity disorder

Attention deficit hyperactivity disorder (ADHD) has been increasingly recognized as a valid adult diagnosis. Yet the impairments related to ADHD in college students have received little scholarly attention. Psychological and academic impairments in college students not previously diagnosed with ADHD were assessed in a retrospective chart review, using specifically defined diagnostic criteria, and compared with a control group. Students with ADHD had a significantly lower mean grade point average, were more likely to be on academic probation, and reported significantly more academic problems. Measures of psychological impairment in the ADHD group were not significantly different from those in the control group. College students diagnosed with ADHD had a specific pattern of academic impairment. The problems of these students, compared with other groups of children and adults with ADHD, appeared to be more related to a type of learning disorder than to the conceptualization of ADHD in the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV).

Over-the-counter psychotropics: a review of melatonin, St John's wort, valerian, and kava-kava

Use and availability of alternative healthcare products have revived in the last few years. The prevalence of supplement use in the United States is largely unknown but is thought to be widespread. In this article, four of the common substances used to treat emotional problems are reviewed. The plant or substance description, clinical indications, evidence of therapeutic efficacy, mechanisms of therapeutic actions, dosages and regimens, different commercially available preparations, and adverse effects and toxicities are described for melatonin, St John's wort, valerian, and kava-kava. That a product is "natural" does not mean that it is either safe or effective. Many supplements are potent drugs that lack sufficient data on safety, dose-response relationships, drug interactions, and purity.

Depression and academic impairment in college students

Impairment from depression and its impact on productivity are of profound societal importance. We report the results of an evaluation of depression and academic impairment in university students, using standardized measures. Sixty-three students completed the Beck Depression Inventory and the work role section from the Social Adjustment Scale-Self Report. Academic impairment, manifested as missed time from class, decreased academic productivity, and significant interpersonal problems at school, was seen in 92% of the students. More severe depression was related to a higher level of impairment. At all levels of depression, affective impairment-inadequacy, distress, and disinterest in school-was more prevalent than was academic impairment. The risk of academic impairment became likely at only moderate-to-severe levels of depression. Discussing the implications of depression with students and aggressively pursuing both medication and nonmedication therapies are essential in preventing the high morbidity associated with untreated depression.