Endovascular thrombectomy for acute ischaemic stroke with established large infarct: multicentre, open-label, randomised trial

BACKGROUND

Recent evidence suggests a beneficial effect of endovascular thrombectomy in acute ischaemic stroke with large infarct; however, previous trials have relied on multimodal brain imaging, whereas non-contrast CT is mostly used in clinical practice.

METHODS

In a prospective multicentre, open-label, randomised trial, patients with acute ischaemic stroke due to large vessel occlusion in the anterior circulation and a large established infarct indicated by an Alberta Stroke Program Early Computed Tomographic Score (ASPECTS) of 3-5 were randomly assigned using a central, web-based system (using a 1:1 ratio) to receive either endovascular thrombectomy with medical treatment or medical treatment (ie, standard of care) alone up to 12 h from stroke onset. The study was conducted in 40 hospitals in Europe and one site in Canada. The primary outcome was functional outcome across the entire range of the modified Rankin Scale at 90 days, assessed by investigators masked to treatment assignment. The primary analysis was done in the intention-to-treat population. Safety endpoints included mortality and rates of symptomatic intracranial haemorrhage and were analysed in the safety population, which included all patients based on the treatment they received. This trial is registered with ClinicalTrials.gov, NCT03094715.

FINDINGS

From July 17, 2018, to Feb 21, 2023, 253 patients were randomly assigned, with 125 patients assigned to endovascular thrombectomy and 128 to medical treatment alone. The trial was stopped early for efficacy after the first pre-planned interim analysis. At 90 days, endovascular thrombectomy was associated with a shift in the distribution of scores on the modified Rankin Scale towards better outcome (adjusted common OR 2·58 [95% CI 1·60-4·15]; p=0·0001) and with lower mortality (hazard ratio 0·67 [95% CI 0·46-0·98]; p=0·038). Symptomatic intracranial haemorrhage occurred in seven (6%) patients with thrombectomy and in six (5%) with medical treatment alone.

INTERPRETATION

Endovascular thrombectomy was associated with improved functional outcome and lower mortality in patients with acute ischaemic stroke from large vessel occlusion with established large infarct in a setting using non-contrast CT as the predominant imaging modality for patient selection.

FUNDING

EU Horizon 2020.

Combined cone-beam CT imaging and microsurgical dissection of cadaver specimens to study cerebral venous anatomy: a technical note

PURPOSE

Cadaver dissections and X-ray based 3D angiography are considered gold standards for studying neurovascular anatomy. We sought to develop a model that utilize the combination of both these techniques to improve current tools for anatomical research, teaching and preoperative surgical planning, particularly addressing the venous system of the brain.

MATERIALS AND METHODS

Seven ethanol-fixed human cadaveric heads and one arm were injected with a latex-barium mixture into the internal jugular veins and the brachial artery. After the ethanol-based fixation, specimens were scanned by high-resolution cone-beam CT and images were post-processed on a 3D-workstation. Subsequent, microsurgical dissections were performed by an experienced neurosurgeon and venous anatomy was compared with relevant 3D venograms.

RESULTS

Latex-barium mixtures resulted in a homogenous cast with filling of the cerebral venous structures down to 150 μm in diameter. The ethanol-based preparation of the cadaveric brains allowed for near-realistic microsurgical maneuverability during dissection. The model improves assessment of the venous system for anatomical education and hands-on surgical training.

CONCLUSION

To our knowledge we describe the first preparation method which combines near-realistic microsurgical dissection of human heads with high-resolution 3D imaging of the cerebral venous system in the same specimens.

Preceding symptoms and temporal development of cortical superficial siderosis in cerebral amyloid angiopathy: a case report

BACKGROUND

We present a case illustrating evolution of symptoms and brain magnetic resonance imaging in cortical superficial siderosis.

CASE PRESENTATION

A 74-year-old man with no prior medical history presented with transient focal neurological episodes with subtle imaging changes. There was no evidence of cortical superficial siderosis. Two weeks later, the patient was readmitted with new episodes, and had developed cortical superficial siderosis adjacent to a cerebral microbleed. Transient focal neurological episode secondary to cortical superficial siderosis was diagnosed together with probable cerebral amyloid angiopathy.

CONCLUSION

Clinical symptoms may precede the development of cortical superficial siderosis prior to being detectable on brain MRI. This case highlights the temporal development of cortical superficial siderosis.

[Invasive treatment of idiopathic intracranial hypertension]

Idiopathic intracranial hypertension (IIH) is characterised by intractable headache, papilloedema, visual symptoms, pulsatile tinnitus and elevated intracranial pressure (ICP). The incidence has increased, most likely due to the simultaneous increase in obesity. This review finds that imaging is centered on ruling out structural causes of elevated ICP as well as visualising classical signs of IIH. Surgery is only indicated for patients at risk of acute vision loss and first line treatment in Denmark is optic nerve sheath fenestration, liquor drainage followed by endovascular treatment.

Delineation atlas of the Circle of Willis and the large intracranial arteries for evaluation of doses to neurovascular structures in pediatric brain tumor patients treated with radiation therapy

BACKGROUND

Survivors of pediatric brain tumors are susceptible to neurovascular disease after radiotherapy, with dose to the chiasm or Circle of Willis (CW) as risk factors. The aims of this study were to develop a delineation atlas of neurovascular structures, to investigate the doses to these structures in relation to tumor location and to investigate potential dose surrogates for the CW dose.

MATERIAL AND METHODS

An atlas of the CW, the large intracranial arteries and the suprasellar cistern (SC) was developed and validated. Thirty proton plans from previously treated pediatric brain tumor patients were retrieved and grouped according to tumor site: 10 central, 10 lateralized, and 10 posterior fossa tumors. Based on the atlas, neurovascular structures were delineated and dose metrics (mean dose (D_mean) and maximal dose (D_max)) to these structures and the already delineated chiasm were evaluated. The agreement between dose metrics to the CW vs. chiasm/SC was investigated. The minimal Hausdorff distance (HD_min) between the target and SC was correlated with the SC D_mean.

RESULTS

The median D_mean/D_max to the CW were 53 Gy(RBE)/55 Gy(RBE) in the central tumors, 18 Gy(RBE)/25 Gy(RBE) in the lateralized tumors and 30 Gy(RBE)/49 Gy(RBE) in the posterior fossa tumors. There was a good agreement between the D_max/D_mean to the CW and the SC for all cases (R²=0.99), while in the posterior fossa group, the CW D_max was underestimated when using the chiasm as surrogate (R²=0.76). Across all patients, cases with HD_min < 10 mm between the target and the SC received the highest SC D_mean.

CONCLUSION

The pattern of dose to neurovascular structures varied with the tumor location. For all locations, SC doses could be used as a surrogate for CW doses. A minimal distance larger than 10 mm between the target and the SC indicated a potential for neurovascular dose sparing.

[Cervical spine fracture in a nine-year-old girl in spite of a normal CT scan]

In this case report, a nine-year-old girl was seen in the emergency department due to neck pain following a trampoline accident ten days ago. She had experienced paraesthesia in her left arm immediately after the accident, but these symptoms disappeared during the first day. A CT scan of the cervical spine was found to be normal. A supplementary MRI was done, showing compression fractures of four vertebrae C7-Th3 besides a torn interspinous ligament between C7 and Th1. The patient was kept in a neck collar for eight weeks. At the end of treatment, she was without any complaints.

Characteristics and outcomes of paediatric patients admitted to a Danish level-1 trauma centre

INTRODUCTION

This study sought to expand the very limited data on Scandinavian paediatric poly-trauma patients by charactering patients from this population admitted to a Danish level-1 trauma centre.

METHODS

This retrospective cohort study included all patients 15 years or younger who were admitted to the trauma centre at Aarhus University Hospital, Denmark from January 2000 to May 2014. Injury severity was calculated using the Injury Severity Score (ISS). The Wilcoxon rank-sum test was used to determine significant differences between sexes.

RESULTS

A total of 880 children (499 boys and 391 girls) were included. No significant sex-related differences were observed in the numbers admitted during the study period, age at admission or severity of injuries. Overall, 30% of the paediatric patients were admitted in the afternoon (3-6 p.m.). The crude death rate was 2.7% of all admissions. Traffic accidents accounted for 48% of all admissions and two-thirds of all deaths. All non-survivors received ISSs of 16 or higher, and 20% of deaths in this group and 42% of overall deaths occurred within the first 24 hours.

CONCLUSIONS

Our study suggests that in Denmark, children admitted to a trauma centre are most likely to have been injured in traffic accidents and/or in the afternoon. Deaths were few and limited to the severely injured children; many survived despite severe injuries.

FUNDING

none.

TRIAL REGISTRATION

not relevant.

Radiation doses to brain substructures associated with cognition in radiotherapy of pediatric brain tumors

Background: Several brain substructures associated with cognition (BSCs) are located close to typical pediatric brain tumors. Pediatric patients therefore have considerable risks of neurocognitive impairment after brain radiotherapy. In this study, we investigated the radiation doses received by BSCs for three common locations of pediatric brain tumor entities. Material and methods: For ten patients in each group [posterior fossa ependymoma (PFE), craniopharyngioma (CP), and hemispheric ependymoma (HE)], the cumulative fraction of BSCs volumes receiving various dose levels were analyzed. We subsequently explored the differences in dose pattern between the three groups and used available dose response models from the literature to estimate treatment-induced intelligence quotient (IQ) decline. Results: Doses to BSCs were found to differ considerably between the groups, depending on their position relative to the tumor. Large inter-patient variations were observed in the ipsilateral structures of the HE groups, and at low doses for all three groups. IQ decline estimates differed depending on the model applied, presenting larger variations in the HE group. Conclusion: While there were notable differences in the dose patterns between the groups, the extent of estimated IQ decline depended more on the model applied. This inter-model variability should be considered in dose-effect assessments on cognitive outcomes of pediatric patients.

Non-aneurysmal subarachnoid hemorrhage: When is a second angiography indicated?

Purpose Repeat imaging in patients with non-aneurysmal subarachnoid hemorrhage (NASAH) remains controversial. We aim to report our experience with NASAH with different hemorrhage patterns, and to investigate the need for further diagnostic workup to determine the underlying cause of hemorrhage. Method We conducted a retrospective analysis of all spontaneous SAH with an initial negative computed tomography (CT) with angiography (CTA) and/or digital subtraction angiography (DSA) from October 2011 through May 2017. According to the bleeding pattern on the admission CT scan, NASAH was divided into two subgroups: (1) perimesencephalic SAH (PMSAH) and (2) non-perimesencephalic SAH (nPMSAH). Radiological data included the admission CT, CTA, DSA, and magnetic resonance imaging (MRI) with angiography (MRA). Results Seventy-four patients met the inclusion criteria. Thirty-nine (52.7%) patients had PMSAH on the initial CT scan, and 35 (47.3%) had nPMSAH. All underwent CTA and/or DSA revealing no vascular abnormalities. Forty-seven (63.5%) patients underwent subsequent diagnostic workup. DSA was performed in all patients at least once. No abnormalities were found on the repeat DSA or other radiological follow-up studies except in one (1.4%) patient with nPMSAH, in whom a follow-up DSA revealed a small saccular anterior choroidal artery aneurysm, considered to be the source of hemorrhage. Conclusion A repeat DSA may not be needed in case of PMSAH, if the initial negative DSA is technically adequate with absence of hematoma and vasospasm. In contrast, a follow-up DSA should be mandatory for confirming or excluding vascular pathology in case of nPMSAH in order to prevent rebleeding.

A Case of Tranexamic Acid as Adjunctive Treatment for Chronic Subdural Hematoma with Multiple Recurrences

Patient: Male, 64

Final Diagnosis: Chronic subdural hematoma

Symptoms: Aphasia • headache • paresis

Medication: —

Clinical Procedure: Burr hole evacuation • Tranexamic acid

Specialty: Neurosurgery

Endovascular Treatment of Basilar Artery Thrombosis Secondary to Bilateral Vertebral Artery Dissection with Symptom Onset Following Cervical Spine Manipulation Therapy

Patient: Female, 37

Final Diagnosis: Vertebral artery dissection

Symptoms: Neck pain and focal neurological deficits

Medication: No previous

Clinical Procedure: Endovascular thrombectomy

Specialty: Neurology

Non-survivors after admission to trauma centre

INTRODUCTION

Knowledge of trauma patients is often based on US studies. However, these may not be representative of the Scandinavian population. Knowing which trauma patients are at risk of dying might help us target and optimise their treatment. The purpose of this study was to examine the epidemiological characteristics and the mortality among patients who did not survive after being admitted to a Danish trauma centre.

MATERIAL AND METHODS

This was a historical cohort study. The study population comprised trauma patients admitted to Aarhus University Hospital from January 2000 to July 2011. Those admitted alive and who subsequently died while still at the hospital were analysed as dead. All injuries were scored according to the abbreviated injury scale, and the mechanisms of trauma were categorised by the NOMESCO classification system. The annual odds ratios (OR) for death were calculated adjusting for potential confounders using logistic regression analysis.

RESULTS

During the study period, a total of 6,299 trauma patients were admitted of whom 280 (4.4%) died. The OR for death was significantly lower in 2004 than in the remaining years, but there was no difference in mortality during the rest of the study period. Most patients died within the first 24 hours (67%), and 87% died within the first week. The primary cause of death was damage to the central nervous system (56%) and exsanguination (13%).

CONCLUSION

Survival has not been improved in the period from January 2000 to July 2011. Initiatives that could potentially improve survival include the introduction of an increased focus on older patients, treatment within the first 24 hours and treatment of cerebral and vascular injuries.

FUNDING

not relevant.

TRIAL REGISTRATION

not relevant.

Suppression of epileptiform activity by a single short-duration electric field in rat hippocampus in vitro

The mechanisms behind the therapeutic effects of electrical stimulation of the brain in epilepsy and other disorders are poorly understood. Previous studies in vitro have shown that uniform electric fields can suppress epileptiform activity through a direct polarizing effect on neuronal membranes. Such an effect depends on continuous DC stimulation with unbalanced charge. Here we describe a suppressive effect of a brief (10 ms) DC field on stimulus-evoked epileptiform activity in rat hippocampal brain slices exposed to Cs+ (3.5 mM). This effect was independent of field polarity, was uncorrelated to changes in synchronized population activity, and persisted during blockade of synaptic transmission with Cd2+ (500 μM). Antagonists of A1, P2X, or P2Y receptors were without effect. The suppressive effect depended on the alignment of the external field with the somato-dendritic axis of CA1 pyramidal cells; however, temporal coincidence with the epileptiform activity was not essential, as suppression was detectable for up to 1 s after the field. Pyramidal cells, recorded during epileptiform activity, showed decreased discharge duration and truncation of depolarizing plateau potentials in response to field application. In the absence of hyperactivity, the applied field was followed by slow membrane potential changes, accompanied by decreased input resistance and attenuation of the depolarizing afterpotential following action potentials. These effects recovered over a 1-s period. The study suggests that a brief electric field induces a prolonged suppression of epileptiform activity, which can be related to changes in neuronal membrane properties, including attenuation of signals depending on the persisting Na+ current.

Direct mail improves knowledge of basic life support guidelines in general practice: a randomised study

BACKGROUND

Implementation of new guidelines into clinical practice is often incomplete. Direct mail is a simple way of providing information to physicians and may improve implementation of new guidelines on basic life support (BLS). The aim of this study was to describe knowledge of the most recent European Resuscitation Council (ERC) Guidelines for BLS among general practitioners (GPs) and investigate whether direct mail improves theoretical knowledge of these guidelines.

METHODS

All general practice clinics (n=351) in Central Denmark Region were randomised to receive either direct mail (intervention) or no direct mail (control). The direct mail consisted of the official ERC BLS/AED poster and a cover letter outlining changes in compression depth and frequency in the new guidelines. In general practice clinics randomised to intervention, every GP received a direct mail addressed personally to him/her. Two weeks later, a multiple-choice questionnaire on demographics and BLS guidelines were mailed to GPs in both groups.

RESULTS

In total, 830 GPs were included in this study (direct mail, n=408; control, n=422). The response rate was 58%. The majority (91%) of GPs receiving direct mail were familiar with BLS Guidelines 2010 compared to 72% in the control group (P<0.001). Direct mail improved knowledge of the new recommended chest compression depth (67% vs. 40%, P<0.001) and chest compression frequency (62% vs. 40%, P<0.001).

CONCLUSION

Direct mail improved knowledge of changes in BLS guidelines and thus facilitated the implementation of this knowledge into clinical practice. Resuscitation councils and medical societies may consider using direct mail as a simple strategy to facilitate implementation of changes in clinical guidelines.

[Peer-led training in basic life support and resuscitation using an automatic external defibrillator]

Peer-led training has been identified as a useful tool for delivering undergraduate healthcare training. In this paper we describe the implementation of the European Resuscitation Council BLS/AED Course as a peer-led training program for medical students.

Analysis of the amino terminus of maize branching enzyme II by polymerase chain reaction random mutagenesis

Maize endosperm branching enzyme II (mBEII) plays a pivotal role in determining the quality of starch by catalyzing the synthesis of the alpha-1,6-branch points. While the central (alpha/beta)8-barrel and the C-terminal domains of mBEII have been analyzed previously, the possible role of its amino terminus in catalysis is still poorly understood. Because the amino terminus of mBEII shares very little sequence homology with other amylolytic enzymes, the Met1-Gly276 region of mBEII was randomly mutagenized under error-prone PCR conditions. Subsequent screening by a heterologous complementation system, utilizing an Escherichia coli strain devoid of the endogenous glycogen branching enzyme (glgB-), led to the recovery of mBEII mutants with altered iodine-staining patterns and reduced branching enzyme activities. The NR-625 mutant enzyme, which lacks the N-terminal 39 residues of mBEII due to a frameshift mutation introduced during the random mutagenesis, retained more than 70% of the wild-type activity. The chain transfer pattern and substrate preference of the truncated enzyme were almost identical to those of the wild-type mBEII. It appears that the N-terminal 39 residues of mBEII are neither required for catalysis nor involved in chain transfer. On the other hand, the Gln-to-Arg substitution at position 270 of mBEII resulted in the loss of more than 90% of branching activity. The Gln270 of mBEII, located at the beginning of the (alpha/beta)8-barrel domain, may be required for maximum enzyme activity.

Breakdown of universality in transitions to spatiotemporal chaos

We show that the transition from laminar to active behavior in extended chaotic systems can vary from a continuous transition in the universality class of directed percolation with infinitely many absorbing states to what appears as a first-order transition. The latter occurs when finite lifetime nonchaotic structures, called "solitons," dominate the dynamics. We illustrate this scenario in an extension of the deterministic Chaté-Manneville coupled map lattice model and in a soliton including variant of the stochastic Domany-Kinzel cellular automaton.

Tyrosine Residue 300 Is Important for Activity and Stability of Branching Enzyme from Escherichia coli

Branching enzyme belongs to the alpha-amylase family, which includes enzymes that catalyze hydrolysis or transglycosylation at alpha-(1,4)- or alpha-(1,6)-glucosidic linkages. In the alpha-amylase family, four highly conserved regions are proposed to make up the active site. From amino acid sequence analysis a tyrosine residue is completely conserved in the alpha-amylase family. In Escherichia coli branching enzyme, this residue (Y300) is located prior to the conserved region 1. Site-directed mutagenesis of the Y300 residue in E. coli branching enzyme was used in order to study its possible function in branching enzymes. Replacement of Y300 with Ala, Asp, Leu, Ser, and Trp resulted in mutant enzymes with less than 1% of wild-type activity. A Y300F substitution retained 25% of wild-type activity. Kinetic analysis of Y300F showed no effect on the Km value. The heat stability of Y300F was analyzed, and this was lowered significantly compared to that of the wild-type enzyme. Y300F also showed lower relative activity at elevated temperatures compared to wild-type. Thus, these results show that Tyr residue 300 in E. coli branching enzyme is important for activity and thermostability of the enzyme.

Limited proteolysis of branching enzyme from Escherichia coli

Branching enzyme is involved in determining the structure of starch and glycogen. It catalyzes the formation of branch points by cleavage and transfer of alpha-1,4-glucan chains to alpha-1,6 branch points. Branching enzyme belongs to the amylolytic family of enzymes containing four conserved regions in a central (alpha/beta)8-barrel. Limited proteolysis of the branching enzyme from Escherichia coli (84 kDa) by proteinase K produced a truncated protein of 70-kDa, which still retained 40-60% of branching activity, depending on the type of assay used. Amino acid sequencing showed that the 70-kDa protein lacked 111 or 113 residues at the amino terminal, whereas the carboxy terminal was still intact. We purified this truncated enzyme to homogeneity and analyzed its properties. The enzyme had a three- to fourfold lower catalytic efficiency than the native enzyme, whereas the substrate specificity was unaltered. Furthermore, a branching enzyme with 112 residues deleted at the amino terminal was constructed by recombinant technology and found to have properties identical to those of the proteolyzed enzyme.

Inhibition of the mitogen activated protein (MAP) kinase cascade potentiates cell killing by low dose ionizing radiation in A431 human squamous carcinoma cells

The molecular mechanism(s) by which tumor cells survive after exposure to ionizing radiation are not fully understood. Exposure of A431 cells to low doses of radiation (1 Gy) caused prolonged activations of the mitogen activated protein (MAP) kinase and stress activated protein (SAP) kinase pathways, and induced p21(Cip-1/WAF1) via a MAP kinase dependent mechanism. In contrast, higher doses of radiation (6 Gy) caused a much weaker activation of the MAP kinase cascade, but a similar degree of SAP kinase cascade activation. In the presence of MAP kinase blockade by the specific MEK1 inhibitor (PD98059) the basal activity of the SAP kinase pathway was enhanced twofold, and the ability of a 1 Gy radiation exposure to activate the SAP kinase pathway was increased approximately sixfold 60 min after irradiation. In the presence of MAP kinase blockade by PD98059 the ability of a single 1 Gy exposure to cause double stranded DNA breaks (TUNEL assay) was enhanced at least threefold over the following 24-48 h. The increase in DNA damage within 48 h was also mirrored by a similar decrease in A431 cell growth as judged by MTT assays over the next 4-8 days following radiation exposure. This report demonstrates that the MAP kinase cascade is a key cytoprotective pathway in A431 human squamous carcinoma cells which is activated in response to clinically used doses of ionizing radiation. Inhibition of this pathway potentiates the ability of low dose radiation exposure to induce cell death in vitro.

The mitogen-activated protein (MAP) kinase cascade can either stimulate or inhibit DNA synthesis in primary cultures of rat hepatocytes depending upon whether its activation is acute/phasic or chronic

Bailie et al. [In Vitro Cell Dev. Biol. (1992) 28A, 621-624] reported that primary cultures of rat hepatocytes possess low affinity binding sites for nerve growth factor (NGF). NGF treatment of primary cultures of rat hepatocytes with a maximally effective concentration of NGF (20 ng/ml, 0.8 nM) caused acute phasic activation of Raf-1 and p42(MAPkinase), and a smaller sustained activation of B-Raf. The transient increase in Raf-1 and p42(MAPkinase) activity returned to baseline within approximately 30 min. NGF treatment of hepatocytes did not induce expression of cyclin dependent kinase (cdk) inhibitor proteins, but instead stimulated cdk2 activity and increased [3H]thymidine incorporation into DNA. In contrast to hepatocytes, NGF treatment of PC12 pheochromocytoma cells caused large sustained activations of B-Raf and p42(MAPkinase), and a lower phasic activation of Raf-1. The sustained activations of B-Raf and p42(MAPkinase) were for more than 5 h. Treatment of PC12 cells with NGF increased p21(Cip1/WAF-1) expression, reduced cdk2 activity and inhibited DNA synthesis, the opposite to the effects of NGF treatment of hepatocytes. However when p42(MAPkinase) was chronically activated in hepatocytes, via infection with an inducible oestrogen receptor-Raf-1 fusion protein, expression of p21(Cip-1/WAF1) and p16(INK4a) cdk inhibitor proteins increased, cdk2 activity decreased, and DNA synthesis decreased. Equally, treatment of hepatocytes with 50 mM ethanol elevated the basal activity of p42(MAPkinase) and temporally extended the ability of NGF treatment to activate p42(MAPkinase). Ethanol and NGF co-treatment increased expression of p21(Cip-1/WAF1) and p16(INK4a) cdk inhibitor proteins and decreased hepatocyte DNA synthesis. These data demonstrate that NGF can cause either acute/phasic or sustained activation of the MAP kinase cascade in different cell types. Acute activation of the MAP kinase cascade correlated with increased DNA synthesis. In contrast, sustained activation of the MAP kinase cascade correlated with increased expression of cdk inhibitor proteins, a reduction in cdk activity, and an inhibition of DNA synthesis. These data suggest a general mechanism exists where acute activation of the MAP kinase cascade promotes G1 progression/S phase entry and that chronic activation of the MAP kinase cascade inhibits this process.

Positive and negative regulation of JNK1 by protein kinase C and p42(MAP kinase) in adult rat hepatocytes

The role of protein kinase C (PKC) and p42(MAP kinase) signaling in the regulation of proliferation and apoptosis was investigated in freshly isolated and primary cultured rat hepatocytes. Acute treatment of freshly isolated hepatocytes with phenylephrine and EGF caused rapid phasic activations of p42(MAP kinase) and JNK1. Acute pre-treatment of hepatocytes with the PKC inhibitors sphingosine, chelerythrine and bis-indolylmaleimide abolished the ability of phenylephrine, but not EGF, to activate p42(MAP kinase) and JNK1. Acute pretreatments with all of the PKC inhibitors alone increased JNK1 basal activity approximately 2-fold. Acute treatments of primary cultures of hepatocytes with an inhibitor of MEK1 activation (PD98059) also caused inhibition of p42(MAP kinase) and a approximately 2-fold activation of JNK1. These data demonstrate that PKC can function as both a proximal activator and a distal inhibitor of signaling through the JNK1/SAP kinase pathway. Treatments (4 h) of primary cultured hepatocytes with sphingosine, chelerythrine, bis-indolylmaleimide and PD98059 did not induce apoptosis as judged by propidium iodide staining. Similar acute treatments of HepG2 cells rapidly induced cell death. These data demonstrate that acute inhibition of either PKC or p42(MAP kinase) function is sufficient to rapidly induce apoptosis in transformed, but not in non-transformed hepatocytes.

Effect of AS101 on bryostatin 1-mediated differentiation induction, cell cycle arrest, and modulation of drug-induced apoptosis in human myeloid leukemia cells

Based upon earlier reports of synergism in cells of lymphoid origin, we have examined interactions between the organotellurium compound AS101 and the protein kinase C (PKC) activator bryostatin 1 with respect to differentiation and Ara-C-induced apoptosis in human myeloid leukemia cells (HL-60). Although preincubation with bryostatin 1 (10 nM) for 24 h significantly increased DNA fragmentation and apoptosis in cells subsequently treated with 10 microM Ara-C for 6 h, this effect was not enhanced by co-administration of AS101 (1.5 microM). However, while exposure of cells to AS101 or bryostatin 1 alone for 72 h was ineffective in inducing cellular maturation, combined treatment resulted in the induction of differentiated features in a subset of cells, manifested by an increase in cell adherence, CD11b expression, cytoplasmic granularity and cell spreading. In addition, cells exposed to the combination of AS101 and bryostatin 1, in contrast to cells incubated with these agents individually, displayed a significant decline in the S-phase and a corresponding increase in the G0/G1 cell populations. These events were accompanied by an increase in protein expression of the cyclin-dependent kinase inhibitor, p21 (WAF1/CIP1/MDA6), and a decline in expression of the c-myc protein. AS101 failed to increase intracellular free Ca2+ ([Ca2+]i) in HL-60 cells, or reverse the profound PKC down-regulation induced by bryostatin 1. Whereas treatment of cells with 1.5 microM AS101 or 10 nM bryostatin 1 for 24 h exerted minimal growth inhibitory effects, combined exposure to these agents reduced colony formation by over 70%. Finally, although addition of AS101 did not potentiate apoptosis induced by the bryostatin 1/Ara-C combination, it did lead to a further reduction in clonogenicity. Together, these findings demonstrate that AS101 partially restores the ability of bryostatin 1 to trigger a differentiation program in an otherwise unresponsive HL-60 cell line, possibly by facilitating bryostatin 1-mediated G1 arrest. They also indicate that AS101 potentiates the antiproliferative effects of bryostatin 1 administered alone or in combination with Ara-C through a mechanism other than, or in addition to, induction of apoptosis.

Analysis of a cation-transporting ATPase of Plasmodium falciparum

We have cloned and characterised one gene, PfATPase4 which encodes a P-type ATPase containing all the primary sequence motifs characteristic of this class of transmembrane ion transporters, and also a fragment of a second P. falciparum P-type ATPase pseudogene (PfATPase5). Analysis of conserved domains and motifs of specific ATPases reveals that PfATPase4 is most analogous to Ca2+ ATPases of the endoplasmic reticulum. The PfATPase4 gene gives rise to a transcript of 8 kb shortly after erythrocyte invasion. Although this mRNA is not detected in later stages, the protein detected immunologically at 190 kDa persists throughout and is detected in free merozoites. Immunofluorescence microscopy reveals that the PfATPase4 protein is concentrated in discrete compartments at the periphery of the parasite. Detailed sequence and structural analyses of these and the other P-type ATPases of P. falciparum described previously, reveals that they comprise an unusual family in several respects. Firstly, the large number of non-homologous genes so far characterised reflects the complexities of ionic regulation in the diverse environments encountered by the parasite. Secondly, the plasmodial P-type ATPase family may be classified both at primary sequence and structural levels into two distinct groups-those typical of P-type ATPases (including PfATPase4) and those which are much more divergent. A third complexity is illustrated by the fact that one of the other members [1] here termed PfATPase6, has an even greater similarity to the sarcoplasmic reticulum Ca2+ ATPases than does PfATPase4, which raises questions about the possible functional relationship between these two members.

Studies on fenestral contraction in rat liver endothelial cells in culture

Liver endothelial cells possess fenestrae, which are pores supported by a cytoskeleton ring composed of actin and myosin. Fenestrae are dynamic structures that can contract or dilate, although the mechanism for this phenomenon remains to be elucidated. Staining of actin and/or of myosin permitted measurement of fenestral diameter and area in cultured rat liver endothelial cells using digitized video-intensified fluorescence microscopy with image analysis. Within 1 minute of incubation with 0.1 micromol/L serotonin, fenestral diameter and area decreased by 24 +/- 5% and 56 +/- 7%, respectively. Contraction of fenestrae by serotonin was inhibited by chelation of extracellular Ca2+ with EGTA and by addition of Ca2+ channel blockers, such as dilthiazem and verapamil. The response of fenestrae to serotonin was mimicked by addition of a Ca2+ ionophore, A23187. Serotonin inhibited cAMP production, had no effect on inositol phosphate production, and activated phospholipase A2, causing release of arachidonic acid. These results suggest that contraction of fenestrae is associated with Ca2+ influx. In response to 0.1 micromol/serotonin, intracellular Ca2+ levels increased within 3 to 5 seconds from 150 nmol/L to >400 nmol/l followed by rapid phosphorylation of the 20-kd subunit of myosin light chain; both events dependent on extracellular Ca2+.

Isolation and sequence analysis of a cDNA encoding an adenine nucleotide translocator from Plasmodium falciparum

A cDNA clone encoding the polypeptide for Plasmodium falciparum adenine nucleotide translocator (ANT) was isolated by screening a cDNA library with a 150 base pair fragment of genomic DNA which had been enzymatically amplified using two oligonucleotide primers designed from conserved regions of ANT's from other sources. The deduced amino acid sequence of the P. falciparum cloned insert was highly homologous to ANT of other organisms. Features of the sequence are discussed with reference to the targeting and membrane insertion of ANT. The protein has a molecular mass of 35 kDa as predicted from the 303 amino acids encoded in the open reading frame.

[Therapeutic riding for persons with somatic disabilities]

Therapeutic riding for somatic disabled has been established as one of the treatment modalities at Beitostølen Health Sports Centre ever since it opened in 1970. The accumulated experience indicates positive effects of the treatment, on empirical grounds, but there is a need of further evaluation and controlled studies. The authors briefly review the principle of the treatment and present the results of a study on the level of pain in patients with Bechterew's disease before and after treatment.

Carbachol-induced cytosolic free Ca2+ increases in T84 colonic cells seen by microfluorimetry

Changes in cytosolic free Ca2+ ([Ca2+]i) in response to the secretagogue carbachol have been characterized in the human colon cancer cell line T84, a model Cl- secretory cell. In this study, [Ca2+]i was determined with the fluorescence indicator fura-2 at the single-cell level with a fluorescent microscope-imaging system. Basal [Ca2+]i in T84 cells in Ringer-HCO3 solution was 76 +/- 4 nM and was decreased by exposure to Ca2+ free solution or 25 microM verapamil. The cholinergic agonist carbachol caused a concentration-dependent rise in [Ca2+]i with a Km of 4 microM and a peak increase in [Ca2+]i of approximately 50 nM. The onset of the [Ca2+]i increase was within 3 s, occurred uniformly among cells, and peaked at 10-15 s. The increase in [Ca2+]i was heterogenous in the length of time the [Ca2+]i remained elevated above basal, and cell responses could be divided into at least two groups on that basis. Blocking the contributions of intracellular Ca2+ with dantrolene inhibited the increase in [Ca2+]i as early as could be determined, whereas blocking the extracellular contribution with ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA), verapamil, or nifedipine inhibited a slightly later increase in [Ca2+]i. In conclusion, the initial detectable increase in [Ca2+]i caused by carbachol is due to the release of Ca2+ from internal stores, whereas the contribution of extracellular Ca2+ occurs later and at least partially involves a nifedipine- and verapamil-sensitive process.

The interaction of lanthanides with isolated sarcoplasmic reticulum vesicles from rabbit skeletal muscle

The interaction of lanthanides with isolated sarcoplasmic reticulum (SR) vesicles from rabbit skeletal muscle and the effects of lanthanides on 45Ca2+ uptake by the vesicles were studied. 153Gd3+ was taken up by the vesicles in the absence of ATP and oxalate in a time-dependent manner, reaching a maximum total accumulation of 380 nmol 153Gd3+/mg protein after 20 min with 200 microM 153Gd3+. This 153Gd3+ accumulation was not washed out by 1 mM EGTA. The addition of ATP induced the release of 87% of the bound 153Gd3+, leaving behind irreversibly-accumulated 153Gd3+. Pre-incubation of the vesicles with lanthanides in the absence of ATP and oxalate inhibited 45Ca2+ uptake without affecting Ca2+-ATPase activity. The percent inhibition of 45Ca2+ uptake increased with length of pre-incubation of the vesicles with lanthanides, reaching 33% after 20 min of pre-incubation. Increasing the 45Ca2+ concentration or adding ATP or oxalate to the preincubation medium abolished these inhibitory effects on 45Ca2+ uptake.