Idiopathic acute transverse myelitis: a clinical study and prognostic markers in 45 cases

Objective The Transverse Myelitis Consortium Working Group has proposed new diagnostic criteria for idiopathic acute transverse myelitis (ATM). We reviewed patients admitted to our center diagnosed with myelitis with two objectives: (i) to evaluate the usefulness of these criteria in distinguishing between myelitis as the first episode of multiple sclerosis (MS) and idiopathic ATM; and (ii) to analyse the clinical and laboratory variables that may be used as functional prognostic markers.

Methods We selected patients who met the criteria. We recorded clinical epidemiological data, patients treated with methylprednisolone, maximal disability reached and disability at final follow-up. We also recorded cerebrospinal fluid (CSF) data and the number of levels affected in the spinal magnetic resonance imaging (MRI).

Results Twenty-four patients fulfilled the criteria for definite ATM and 21 for possible ATM. Five patients converted to MS. Mean follow-up time was 3.5 years. There was an association between younger patients and female patients with conversion to MS. The highest Rankin score reached and increased CSF glucose levels were associated with a poor outcome. In multivariate analysis, only the admission Rankin score was associated with outcome.

Conclusions (i) About 10% of patients who met the criteria may convert to MS; and (ii) admission Rankin score was the only independent prognostic factor found.

Association Between Time to Reperfusion and Outcome Is Primarily Driven by the Time From Imaging to Reperfusion

Background and Purpose—

A progressive decline in the odds of favorable outcome as time to reperfusion increases is well known. However, the impact of specific workflow intervals is not clear.

Methods—

We studied the mechanical thrombectomy group (n=103) of the prospective, randomized REVASCAT (Randomized Trial of Revascularization With Solitaire FR Device Versus Best Medical Therapy in the Treatment of Acute Stroke due to Anterior Circulation Large Vessel Occlusion Presenting Within Eight Hours of Symptom Onset) trial. We defined 3 workflow metrics: time from symptom onset to reperfusion (OTR), time from symptom onset to computed tomography, and time from computed tomography (CT) to reperfusion. Clinical characteristics, core laboratory-evaluated Alberta Stroke Program Early CT Scores (ASPECTS) and 90-day outcome data were analyzed. The effect of time on favorable outcome (modified Rankin scale, 0–2) was described via adjusted odds ratios (ORs) for every 30-minute delay.

Results—

Median admission National Institutes of Health Stroke Scale was 17.0 (14.0–20.0), reperfusion rate was 66%, and rate of favorable outcome was 43.7%. Mean (SD) workflow times were as follows: OTR: 342 (107) minute, onset to CT: 204 (93) minute, and CT to reperfusion: 138 (56) minute. Longer OTR time was associated with a reduced likelihood of good outcome (OR for 30-minute delay, 0.74; 95% confidence interval [CI], 0.59–0.93). The onset to CT time did not show a significant association with clinical outcome (OR, 0.87; 95% CI, 0.67–1.12), whereas the CT to reperfusion interval showed a negative association with favorable outcome (OR, 0.72; 95% CI, 0.54–0.95). A similar subgroup analysis according to admission ASPECTS showed this relationship for OTR time in ASPECTS<8 patients (OR, 0.56; 95% CI, 0.35–0.9) but not in ASPECTS≥8 (OR, 0.99; 95% CI, 0.68–1.44).

Conclusions—

Time to reperfusion is negatively associated with favorable outcome, being CT to reperfusion, as opposed to onset to CT, the main determinant of this association. In addition, OTR was strongly associated to outcome in patients with low ASPECTS scores but not in patients with high ASPECTS scores.

Clinical Trial Registration—

URL: http://www.clinicaltrials.gov . Unique identifier: NCT01692379.

Ischaemic stroke in patients treated with oral anticoagulants

INTRODUCTION

Cardioembolic stroke is associated with poorer outcomes. Prevention is based on oral anticoagulant (OAC) therapy. Haemorrhage is the main complication of OACs, which are sometimes ineffective.

PATIENTS AND METHODS

We retrospectively reviewed 1014 consecutive patients who suffered an ischaemic stroke between 2011 and 2013, analysing those who were receiving OAC treatment at stroke onset (107 patients in total) with special attention to aetiology, outcomes, and INR value in the acute phase.

RESULTS

The mean age (SD) was 71.9 (10) years. Patients had been treated with OACs for 5.9 (5.5) years; 98.1% of them were being treated for heart disease. INR was <2 in 77 patients (72%), and 30 patients (28%) had an INR≥2. Nine patients (8.4%) had INR values within the therapeutic range. According to TOAST classification criteria, 88.8% of strokes were cardioembolic and 1.9% were atherothrombotic. Anticoagulation therapy was discontinued in 48 patients (44.9%) due to haemorrhagic transformation (24 patients), extensive infarction (23), or endarterectomy (1). Therapy was resumed in 24 patients (50%) after a mean lapse of 36 days. This was not possible in the remaining patients because of death or severe sequelae. New OACs (NOACs) were prescribed to 9 patients (18.7% of all potential candidates). At 3 months, patients with INR>1.7 in the acute phase exhibited better outcomes than patients with INR≤1.7 (mRS 0-2 in 62% vs 30.8%; death in 10% vs 38.4%; P=.0004).

CONCLUSIONS

Some patients taking OACs suffer ischaemic strokes that are usually cardioembolic, especially if INR is below the therapeutic range. OACs can be resumed without complications, and NOACs are still underused. Despite cases in which treatment is ineffective, outcomes are better when INR is above 1.7 at stroke onset.

Clinical management guidelines for subarachnoid haemorrhage. Diagnosis and treatment

OBJECTIVE

To update the Spanish Society of Neurology's guidelines for subarachnoid haemorrhage diagnosis and treatment.

MATERIAL AND METHODS

A review and analysis of the existing literature. Recommendations are given based on the level of evidence for each study reviewed.

RESULTS

The most common cause of spontaneous subarachnoid haemorrhage (SAH) is cerebral aneurysm rupture. Its estimated incidence in Spain is 9/100 000 inhabitants/year with a relative frequency of approximately 5% of all strokes. Hypertension and smoking are the main risk factors. Stroke patients require treatment in a specialised centre. Admission to a stroke unit should be considered for SAH patients whose initial clinical condition is good (Grades I or II on the Hunt and Hess scale). We recommend early exclusion of aneurysms from the circulation. The diagnostic study of choice for SAH is brain CT (computed tomography) without contrast. If the test is negative and SAH is still suspected, a lumbar puncture should then be performed. The diagnostic tests recommended in order to determine the source of the haemorrhage are MRI (magnetic resonance imaging) and angiography. Doppler ultrasonography studies are very useful for diagnosing and monitoring vasospasm. Nimodipine is recommended for preventing delayed cerebral ischaemia. Blood pressure treatment and neurovascular intervention may be considered in treating refractory vasospasm.

CONCLUSIONS

SAH is a severe and complex disease which must be managed in specialised centres by professionals with ample experience in relevant diagnostic and therapeutic processes.

Potassium starvation induces oxidative stress in Solanum lycopersicum L. roots

The relationship between potassium deficiency and the antioxidative defense system has received little study. The aim of this work was to study the induction of oxidative stress in response to K(+) deficiency and the putative role of antioxidants. The tomato plants were grown in hydroponic systems to determine the role of reactive oxygen species (ROS) in the root response to potassium deprivation. Parameters of oxidative stress (malondialdehyde and hydrogen peroxide (H(2)O(2)) concentration), activities of antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR) and glutathione reductase (GR)) and antioxidant molecules (ascorbate (ASC) and glutathione) were investigated. H(2)O(2) was subcellularly located by laser confocal microscopy after potassium starvation in roots. During the first 24h, H(2)O(2) induced the cascade of the cellular response to low potassium, and ROS accumulation was located mainly in epidermal cells in the elongation zone and meristematic cells of the root tip and the epidermal cells of the mature zones of potassium starved roots. The activity of the antioxidative enzymes SOD, peroxidase and APX in potassium deprivation significantly increased, whereas CAT and DHAR activity was significantly depressed in the potassium starvation treatment compared to controls. GR did not show significant differences between control and potassium starvation treatments. Based on these results, we put forward the hypothesis that antioxidant molecule accumulations probably scavenge H(2)O(2) and might be regenerated by the ASC-glutathione cycle enzymes, such as DHAR and GR.

[Cerebellar infarction: prognosis and complications of vascular territories]

INTRODUCTION

Cerebellar infarction (CI) is uncommon, but may result in severe complications. The aim of our study was to determine the characteristics of patients with CI, as well as their outcomes as regards the territories affected.

PATIENTS AND METHODS

Data were collected from 124 patients admitted to our department during a five-year period, with a radiological diagnosis of CI, and with or without involvement of other brain territories.

RESULTS

The mean age in our series was 65.2 years, with most being male (68.5%). The posterior inferior cerebellar artery (PICA) was the most commonly affected territory at 49.2%, followed by superior cerebellar artery (SCA) at 17.7%, and anterior inferior cerebellar artery (AICA) at 10.5%. There was simultaneous supratentorial involvement in 13.7%, and two or three cerebellar arteries involved in 8.9%. The main aetiology in PICA was atherothrombosis (P=.02). On the other hand, cardio-embolism was the main origin in cases with more than one affected territory (P=.04). No particular aetiology could be found in SCA and AICA. There was haemorrhagic transformation in 29 patients (23.4%), particularly in the PICA and when other territories were involved. There was hydrocephalus in 15 patients (12.1%, 12 of them PICA; P=.02) in 2.9 ± 1.5 days from stroke onset. At discharge, the degree of disability was worse if more than one arterial territory was involved (Rankin ≥ 3, 64% versus 31-36%; P=.05). Four (3.2%) patients died.

CONCLUSIONS

CI is very heterogeneous. Nevertheless, it is noteworthy that PICA infarction is the most frequent type and its aetiology is usually atherothrombotic. Moreover, it is the territory most frequently associated with severe complications, which take place during the first week of the stroke.

Neurosarcoidosis: report of 30 cases and a literature survey

INTRODUCTION

Neurosarcoidosis accounts for approximately 5% of cases of sarcoidosis.

OBJECTIVE

To determine the frequency of Neurosarcoidosis in our setting and analyze the clinical-radiological findings and evolution of 30 patients consecutively diagnosed.

METHODS

The medical records of patients with a diagnosis of Neurosarcoidosis were reviewed, and data regarding the clinical features, ancillary tests performed, treatment, and outcome were recorded. We revised the literature to summarize and discuss the previous clinical series of Neurosarcoidosis.

RESULTS

It accounted for 6.7% of all cases of sarcoidosis. Seven patients had definite diagnosis and 23 had probable diagnosis. The mean age at onset of Neurosarcoidosis was 48.3 years and 66.7% of patients were women. Neurologic clinical features were the first manifestation of Neurosarcoidosis in 70% of cases. Cranial neuropathy was present in 17 patients and 14 of them had facial palsy. The central nervous system was affected in 10 patients and the peripheral nervous system in 5. Chest disease, the most common extraneurologic manifestation, was present in 20 patients. All patients were treated with corticosteroids, and all those with central nervous system involvement had poor outcome.

CONCLUSION

Neurosarcoidosis requires a high degree of suspicion to establish the diagnosis. Central nervous system involvement is associated with a poor prognosis.

Study of arsenopyrite weathering products in mine wastes from abandoned tungsten and tin exploitations

Arsenopyrite-rich wastes from abandoned tungsten and tin exploitations were studied to determine the composition and characteristics of the secondary phases formed under natural weathering conditions so as to assess their potential environmental risk. Representative weathered arsenopyrite-bearing rock wastes collected from the mine dumps were analysed using the following techniques: X-ray powder diffraction (XRD) analysis, polarizing microscopy analysis, electron microprobe analysis (EMPA) and microRaman and Mössbauer spectroscopies. Scorodite, pharmacosiderite and amorphous ferric arsenates (AFA) with Fe/As molar ratios in the range 1.2-2.5 were identified as secondary arsenic products. The former showed to be the most abundant and present in the different studied mining areas. Its chemical composition showed to vary in function of the original surrounding rock mineralogy in such a way that phosphoscorodite was found as the mineral variety present in apatite-containing geoenvirons. Other ever-present weathering phases were goethite and hydrous ferric oxides (HFO), displaying, respectively, As retained amounts about 1 and 20% (expressed as As(2)O(5)). The low solubility of scorodite, the relatively low content of AFA and the formation of compounds of variable charge, mostly of amorphous nature, with high capacity to adsorb As attenuate importantly the dispersion of this element into the environment from these arsenopyrite-bearing wastes.

The Catalan Healthcare Intercultural Mediation Training Project of “la Caixa” Social and Cultural Outreach Projects

Known by many different names-culture broker, community interpreter, medical interpreter, and communication facilitator-the intercultural mediator has as a primary task the facilitation of communication and the therapeutic relationship in the presence of linguistic and/or cultural difference. The Immigration Plan of “la Caixa” Social and Cultural Outreach Projects has undertaken an ambitious project to train all of the cultural mediators in Spain, including both those currently working and those newly entering the field, to meet existing needs. In the first phase of the project, the training was developed in Catalunya, in collaboration with the the Catalan Department of Health, executed by the Psychiatry Department of the Vall d'Hebron University Hospital (Autonomous University of Barcelona) and certified by the Health Studies Institute of the Department of Health. Drawing from the four years experience of the NGO SURT and the Department of Psychiatry of the Vall d'Hebron University Hospital, the program provides 200 hours of theoretical and 1200 hours of practical training. 50 currently employed intercultural mediators and 30 novices are being trained. In subsequent phases the training will be adapted to needs of other autonomous regions of Spain. Modules include medical anthropology, Western biomedicine, community health, linguistic interpretation, cultural competence, professional identity, and ethics. Small group supervision provides a supportive environment to facilitate the application of theory to practice. Finally, high quality training materials were developed specifically for the course. Preliminary evaluations of the project are positive despite some unanticipated complications.

[Frontotemporal lobar degeneration: a descriptive study of 42 patients]

INTRODUCTION

Frontotemporal lobar degeneration (FTLD) is considered to be the second cause of presenile dementia. In spite of the great interest it has generated over the last few years, few studies have been published in our country.

METHODS

A descriptive retrospective study of 42 patients with FTLD evaluated in our unit during the period 1996-2006 was performed.

RESULTS

Thirty one patients presented with frontal variant FTLD (FTD), eigth with non-fluent progressive aphasia and three with semantic dementia. Mean age at onset was 56 years, diagnostic delay 3.5 years and mean survival 6.8 years. 35% had a family history suggestive of dementia. In patients with FTD the clinical expression was a combination of behavioral and personality disorders together with language impairment. Magnetic resonance imaging showed frontal and/or temporal atrophy in 62% of cases and SPECT showed frontal and/or temporal hypoperfusion in 75%. The P301L tau mutation was detected in four patients (two of them siblings) and the A303AfsX57 progranulin mutation in one. Necropsy was performed in five patients, revealing FTLD with ubiquitininmunoreactive inclusions (FTLD-U) and motor neuron disease in two cases, FTLD-U with <<cat's-eye>> shaped intranuclear inclusions in the case with the progranulin mutation and FTLD tauopathy with predominance of 4R tau in the remaining two, both with the P301L mutation.

CONCLUSIONS

Our results are similar to those of the great European series. FTLD must be suspected in presenile patients with prominent behavioral and/or language disorders. Neuroimaging supports the diagnosis in the majority of cases. The huge sociofamiliar impact of FTLD, presenile onset, high frequency of familial history of dementia and possibility of genetic study and counseling highlight its clinical relevance.

Simvastatin in the acute phase of ischemic stroke: a safety and efficacy pilot trial

Although statins are being used for secondary prevention of ischemic stroke, recent experimental data have shown new pleiotropic effects of these drugs responsible for their role in neuroprotection. We conducted a pilot, double-blind, randomized, multicenter clinical trial to study for the first time safety and efficacy of simvastatin in the acute phase of ischemic stroke. Simvastatin/placebo was given at 3-12 h from symptom onset to 60 patients with cortical strokes. Efficacy on the evolution of several inflammation markers [interleukin (IL)-6, IL-8, IL-10, monocyte chemoattractant protein-1, intercellular adhesion molecule-1, vascular cell adhesion molecule-1, C-reactive protein, sApo/Fas, tumor necrosis factor-alpha, E-selectin, L-selectin and nitrites+nitrates] and neurological outcome was evaluated at baseline, day 1, 3, 5, 7 and 90. No differences were found amongst the biomarkers studied regarding treatment allocation. Although simvastatin patients improved significantly by the third day (46.4% vs. 17.9%, P = 0.022), a non-significant increase in mortality and greater proportion of infections (odds ratio 2.4, confidence interval 1.06-5.4) in the simvastatin group were the main safety concerns. Therefore, a larger clinical trial is needed to confirm the net benefit of this therapeutic approach.

[Non-aneurysmal subarachnoid hemorrhage: 60 cases]

INTRODUCTION

Spontaneous subarachnoid hemorrhage (SAH) is idiopathic in 15% of cases. They represent a group whose characteristics are different from those with an aneurysmal etiology. We present a retrospective longterm follow up of 60 patients, analyzing symptomatology, complications and evolution and identify a subgroup of patients with a perimesencephalic pattern (PMP) in computed tomography (CT) for their excellent prognosis.

METHODS

We collected information on 60 patients admitted to our center between 1992 and 2000 and divided them into three groups, according to neuroimage: 26 had a PMP, 28 showed an aneurysmal pattern (AP), and 6 patients had normal TC, with complete arteriographic study. Length of follow-up was 6-24 months.

RESULTS

All of the 26 patients with SAH and PPM pattern were rated grade I-II on the Hunt-Hess scale. None of them had complications during hospital stay and at long term, 22 (84%) were asymptomatic, while 4 (16%) reported cephalea. Out of 28 patients with SAH and AP, 22 were rated Hunt-Hess Scale grade I and II (78%), 5 grade III (18%) and one patient was rated grade IV. Rebleeding caused death in one of them, and two required drainage for hydrocephalia. A total of 68% (19 patients) were asymptomatic and the others complained of cephalea.

CONCLUSIONS

We stress the good evolution of nonaneurysmal SAH at short and long term, especially those following a PMP with absence of complication.

[Plan for stroke healthcare delivery]

INTRODUCTION

All stroke patients should receive the same degree of specialized healthcare attention according to the stage of their disease, independently of where they live, their age, gender or ethnicity.

OBJECTIVE

To create an organized healthcare system able to offer the needed care for each patient, optimizing the use of the existing resource.

METHODS

A committee of 14 neurologists specialized in neurovascular diseases representing different regions of Spain evaluated the available scientific evidence according to the published literature.

RESULTS

During the acute phase, all stroke patients must be evaluated in hospitals that offer access to specialized physicians (neurologists) and the indicated diagnostic and therapeutic procedures. Hospitals that deliver care to acute stroke patients must be prepared to attend these patients and need to arrange a predefined transferring circuit coordinated with the extrahospitalary emergency service. Since resources are limited, they should be structured into different care levels according to the target population. Thus, three types of hospitals will be defined for stroke care: reference stroke hospital, hospital with stroke unit, hospital with stroke team.

Linkage of neutrophil serine proteases and decreased surfactant protein-A (SP-A) levels in inflammatory lung disease

BACKGROUND

In patients with cystic fibrosis (CF) neutrophils are recruited in excess to the airways yet pathogens are not cleared and the patients suffer from chronic infections. Recent studies have shown a deficiency in airway fluids from patients with CF and other inflammatory pulmonary conditions of surfactant protein A (SP-A), a pattern recognition molecule that facilitates uptake of microbes by macrophages and neutrophils.

METHODS

In vitro simulations were used to test the hypothesis that decreased SP-A levels in CF might be the result of degradation by neutrophil serine proteases.

RESULTS

Very low levels of the neutrophil granule serine proteases cathepsin G, elastase, and proteinase-3 rapidly degraded pure SP-A when tested in buffered saline. The order of potency was cathepsin G>elastase>proteinase-3. The addition of cathepsin G or elastase to normal bronchoalveolar lavage (BAL) fluid caused a dose dependent degradation of endogenous native SP-A. Cathepsin G and elastase were present in the BAL fluid from many patients with CF. Simple incubation of protease positive BAL fluid from patients with CF caused a time dependent degradation of added SP-A or, where present, endogenous SP-A. The degradation of SP-A by protease(s) in BAL fluid of patients with CF was abrogated by diisopropylfluorophosphate and monocyte/neutrophil elastase inhibitor.

CONCLUSIONS

The findings strongly suggest that the neutrophil serine proteases cathepsin G and/or elastase and/or proteinase-3 contribute to degradation of SP-A and thereby diminish innate pulmonary antimicrobial defence.

Time-course phosphorylation of the mitogen activated protein (MAP) kinase group of signalling proteins and related molecules following middle cerebral artery occlusion (MCAO) in rats

Recovery from the debilitating effects of ischaemic stroke is variable and unpredictable. To maximize patient recovery, a greater understanding of the molecular mechanisms involved in regulating both apoptosis and the repair processes affecting neuronal protection, particularly in the penumbra region, is desirable. We have previously shown, in human subjects, the increased expression of several growth factors soon after stroke, together with appearance of tyrosine phosphorylated proteins, in particular mitogen activated protein (MAP) kinase (ERK1/2). In this paper, we demonstrate a relatively short-lasting (< 12 h), but substantial increase in expression of phosphorylated proteins, in particular, p-JNK (phosphorylated c-Jun N-terminal kinase) and p-ERK1/2 in both the grey matter penumbra and infarcted tissue of rats, following permanent middle cerebral artery occlusion. p-ERK1/2 was associated with neurones and endothelial cells in the vicinity of the infarct while p-JNK was mainly expressed in neurones. Expression of both p-MEK3/6 and p-p38 MAP kinase was also increased in neurones and astroglia, within 1 h of infarction, p-p38 remaining elevated and associated with neurones and in particular with astroglia in the penumbra region for > 4 days. Evidence suggests that short-term activation of these proteins may be detrimental to neuronal survival, while their transient nature makes them unlikely to support angiogenesis, revascularization and reperfusion over a period of days and weeks. On the other hand, short-medium-term up-regulation of neuronal p-JNK, p-c-Jun, p-Stat-1 and p-p38 might be a factor in the regulation of apoptosis. Therapeutic manipulation of phosphorylation/activation of these and other important signalling intermediates might form the basis of an appropriate treatment to maximize revascularization and neuronal protection after ischaemic stroke.

Comparative functional features of plant potassium HvHAK1 and HvHAK2 transporters

Plant K(+) transporters of the HAK family belong to four rather divergent phylogenetic clusters, although most of the transporters belong to clusters I or II. A simple phylogenetic analysis of fungal and plant HAK transporters suggests that an original HAK gene duplicated even before fungi and plants diverged, generating transporters that at present fulfill different functions in the plant. The HvHAK1 transporter belongs to cluster I and mediates high-affinity K(+) uptake in barley roots, but no function is known for the cluster II transporter, HvHAK2, which is not functional in yeast. The function of HvHAK2 was investigated by constructing HvHAK1-HAK2 chimeric transporters, which were not functional even when they included only short fragments of HvHAK2. Then, amino acids characteristic of cluster II in the N terminus and in the first transmembrane domain were introduced into HvHAK1. All of these changes increased the Rb(+) K(m), introducing minimal changes in the Na(+) K(m), which suggested that HvHAK2 is a low-affinity, Na(+)-sensitive K(+) transporter. Using a K(+)-defective Escherichia coli mutant, we functionally expressed HvHAK2 and found that the predicted characteristics were correct, as well as discovering that the bacterial expression of HvHAK2 is functional at pH 5.5 but not at 7.5. We discuss whether HvHAK2 may be a tonoplast transporter effective for vacuolar K(+) depletion in K(+) starved plants.

An integrated simulator for surgery of the petrous bone

This paper describes work being undertaken as part of the IERAPSI (Integrated Environment for the Rehearsal and Panning of Surgical Intervention) project. The project is focussing on surgery for the petrous bone, and brings together a consortium of European clinicians and technology providers working in this field. The paper presents the results of a comprehensive user task analysis that has been carried out in the first phase of the IERAPSI project, and details the current status of development of a pre operative planning environment and a physically-based surgical simulator.

Activation of MAP kinase (ERK-1/ERK-2), tyrosine kinase and VEGF in the human brain following acute ischaemic stroke

We examined expression of vascular endothelial growth factor (VEGF), phosphorylation of mitogen activated protein kinase (MAP) kinase (ERK1 and ERK2) and tyrosine phosphorylation in 19 patients (aged 58-90 years; mean 75) who died 1-44 days after acute ischaemic stroke. In the grey matter penumbra, 13 of 19 patients showed an increase in MAP kinase tyrosine phosphorylation (ERK1; 2.0- to 8-fold, ERK2; 2.2- to 11-fold) compared with normal contralateral tissue. In almost all cases, ERK-2 phosphorylation was higher than ERK1. Of these 13 patients, 11 also showed a general increase in tyrosine kinase phosphorylation, and eight expressed increased levels of VEGF protein (2.5- to 5-fold). In tissue examined directly from the infarct core, activation of the above proteins was not observed in the, majority of patients. In the white matter, seven of 19 patients (penumbra), and nine of 19 patients (stroke) had an increase in MAP kinase tyrosine phosphorylation (ERK1; 2.0- to 4.6-fold and ERK-2; 2.3- to 5.4-fold respectively) compared with normal contralateral tissue. There was no relationship between activation of MAP kinase and expression of VEGF. Examination of phosphorylated MAP kinase by immunohistochemistry revealed an increase in immunoreactivity in neurones, astroglial cells, reactive microglia and endothelial cells in areas surrounding infarcts, especially in areas with the highest density of microvessels. In conclusion, chronic activation of tyrosine phosphorylated events, in particular redistribution and phosphorylation of MAP kinase (ERK1/ERK2) occurs consistently in the grey matter penumbra of brain tissue following ischaemic stroke, and may be associated with increase in expression of VEGF. These signal transduction events could be important determinants of the extent of neuronal survival and/or angiogenic activity in the recovering brain tissue.

The Arabidopsis HKT1 gene homolog mediates inward Na(+) currents in xenopus laevis oocytes and Na(+) uptake in Saccharomyces cerevisiae

The Na(+)-K(+) co-transporter HKT1, first isolated from wheat, mediates high-affinity K(+) uptake. The function of HKT1 in plants, however, remains to be elucidated, and the isolation of HKT1 homologs from Arabidopsis would further studies of the roles of HKT1 genes in plants. We report here the isolation of a cDNA homologous to HKT1 from Arabidopsis (AtHKT1) and the characterization of its mode of ion transport in heterologous systems. The deduced amino acid sequence of AtHKT1 is 41% identical to that of HKT1, and the hydropathy profiles are very similar. AtHKT1 is expressed in roots and, to a lesser extent, in other tissues. Interestingly, we found that the ion transport properties of AtHKT1 are significantly different from the wheat counterpart. As detected by electrophysiological measurements, AtHKT1 functioned as a selective Na(+) uptake transporter in Xenopus laevis oocytes, and the presence of external K(+) did not affect the AtHKT1-mediated ion conductance (unlike that of HKT1). When expressed in Saccharomyces cerevisiae, AtHKT1 inhibited growth of the yeast in a medium containing high levels of Na(+), which correlates to the large inward Na(+) currents found in the oocytes. Furthermore, in contrast to HKT1, AtHKT1 did not complement the growth of yeast cells deficient in K(+) uptake when cultured in K(+)-limiting medium. However, expression of AtHKT1 did rescue Escherichia coli mutants carrying deletions in K(+) transporters. The rescue was associated with a less than 2-fold stimulation of K(+) uptake into K(+)-depleted cells. These data demonstrate that AtHKT1 differs in its transport properties from the wheat HKT1, and that AtHKT1 can mediate Na(+) and, to a small degree, K(+) transport in heterologous expression systems.

Genetic selection of mutations in the high affinity K+ transporter HKT1 that define functions of a loop site for reduced Na+ permeability and increased Na+ tolerance

Potassium is an important macronutrient required for plant growth, whereas sodium (Na+) can be toxic at high concentrations. The wheat K+ uptake transporter HKT1 has been shown to function in yeast and oocytes as a high affinity K+-Na+ cotransporter, and as a low affinity Na+ transporter at high external Na+. A previous study showed that point mutations in HKT1, which confer enhancement of Na+ tolerance to yeast, can be isolated by genetic selection. Here we report on the isolation of mutations in new domains of HKT1 showing further large increases in Na+ tolerance. By selection in a Na+ ATPase deletion mutant of yeast that shows a high Na+ sensitivity, new HKT1 mutants at positions Gln-270 and Asn-365 were isolated. Several independent mutations were isolated at the Asn-365 site. N365S dramatically increased Na+ tolerance in yeast compared with all other HKT1 mutants. Cation uptake experiments in yeast and biophysical characterization in Xenopus oocytes showed that the mechanisms underlying the Na+ tolerance conferred by the N365S mutant were: reduced inhibition of high affinity Rb+ (K+) uptake at high Na+ concentrations, reduced low affinity Na+ uptake, and reduced Na+ to K+ content ratios in yeast. In addition, the N365S mutant could be clearly distinguished from less Na+-tolerant HKT1 mutants by a markedly decreased relative permeability for Na+ at high Na+ concentrations. The new mutations contribute to the identification of new functional domains and an amino acid in a loop domain that is involved in cation specificity of a plant high affinity K+ transporter and will be valuable for molecular analyses of Na+ transport mechanisms and stress in plants.