Migraine-Associated Common Genetic Variants Confer Greater Risk of Posterior vs. Anterior Circulation Ischemic Stroke☆

OBJECTIVE

To examine potential genetic relationships between migraine and the two distinct phenotypes posterior circulation ischemic stroke (PCiS) and anterior circulation ischemic stroke (ACiS), we generated migraine polygenic risk scores (PRSs) and compared these between PCiS and ACiS, and separately vs. non-stroke control subjects.

METHODS

Acute ischemic stroke cases were classified as PCiS or ACiS based on lesion location on diffusion-weighted MRI. Exclusion criteria were lesions in both vascular territories or uncertain territory; supratentorial PCiS with ipsilateral fetal posterior cerebral artery; and cases with atrial fibrillation. We generated migraine PRS for three migraine phenotypes (any migraine; migraine without aura; migraine with aura) using publicly available GWAS data and compared mean PRSs separately for PCiS and ACiS vs. non-stroke control subjects, and between each stroke phenotype.

RESULTS

Our primary analyses included 464 PCiS and 1079 ACiS patients with genetic European ancestry. Compared to non-stroke control subjects (n=15396), PRSs of any migraine were associated with increased risk of PCiS (p=0.01-0.03) and decreased risk of ACiS (p=0.010-0.039). Migraine without aura PRSs were significantly associated with PCiS (p=0.008-0.028), but not with ACiS. When comparing PCiS vs. ACiS directly, migraine PRSs were higher in PCiS vs. ACiS for any migraine (p=0.001-0.010) and migraine without aura (p=0.032-0.048). Migraine with aura PRS did not show a differential association in our analyses.

CONCLUSIONS

Our results suggest a stronger genetic overlap between unspecified migraine and migraine without aura with PCiS compared to ACiS. Possible shared mechanisms include dysregulation of cerebral vessel endothelial function.

ClimApp-Integrating Personal Factors with Weather Forecasts for Individualised Warning and Guidance on Thermal Stress

This paper describes the functional development of the ClimApp tool (available for free on iOS and Android devices), which combines current and 24 h weather forecasting with individual information to offer personalised guidance related to thermal exposure. Heat and cold stress assessments are based on ISO standards and thermal models where environmental settings and personal factors are integrated into the ClimApp index ranging from -4 (extremely cold) to +4 (extremely hot), while a range of -1 and +1 signifies low thermal stress. Advice for individuals or for groups is available, and the user can customise the model input according to their personal situation, including activity level, clothing, body characteristics, heat acclimatisation, indoor or outdoor situation, and geographical location. ClimApp output consists of a weather summary, a brief assessment of the thermal situation, and a thermal stress warning. Advice is provided via infographics and text depending on the user profile. ClimApp is available in 10 languages: English, Danish, Dutch, Swedish, Norwegian, Hellenic (Greek), Italian, German, Spanish and French. The tool also includes a research functionality providing a platform for worker and citizen science projects to collect individual data on physical thermal strain and the experienced thermal strain. The application may therefore improve the translation of heat and cold risk assessments and guidance for subpopulations. ClimApp provides the framework for personalising and downscaling weather reports, alerts and advice at the personal level, based on GPS location and adjustable input of individual factors.

Increasing incidence of colorectal cancer among the younger population in Sweden

Background

The incidence of colorectal cancer in patients aged less than 50 years is increasing in Western countries. This population‐based study investigated the age‐ and sex‐specific incidence of colorectal cancer over time in Sweden, and characterized trends in tumour localization and stage at diagnosis.

Methods

Patients diagnosed with colorectal cancer between 1970 and 2016 were identified from the Swedish Cancer Registry, and categorized by sex, age and tumour location. The incidence and average annual percentage change (AAPC) were estimated and compared between age groups.

Results

There was an overall increase in the incidence of colorectal cancer between 1970 and 2006, but a decrease in 2006–2016 (AAPC −0·55 (95 per cent c.i. −1·02 to −0·07) per cent). The largest increase in colonic cancer was in 1995–2005 in women aged less than 50 years (AAPC 2·30 (0·09 to 4·56) per cent versus 0·04 (−1·35 to 1·44) and − 0·67 (−1·62 to 0·28) per cent in women aged 50–74 and 75 years or more respectively). Since 1990, rectal cancer increased in patients of both sexes aged below 50 years, with higher AAPC values in women (2006–2016: 2·01 (−1·46 to 5·61) per cent versus 0·20 (−2·25 to 2·71) per cent in men). Younger patients were more likely than those aged 50–74 and 75 years or more to present with stage III–IV colonic (66·2, 57·6 and 49·6 per cent respectively) and rectal (61·2, 54·3 and 51·3 per cent) cancer. From the mid 1990s, rates of proximal and distal colorectal cancer, and rectal cancer were increased in patients aged less than 50 years.

Conclusion

The overall incidence of colorectal cancer in Sweden decreased in the past decade. However, in patients under 50 years of age the incidence of colorectal cancer – proximal, distal and rectal – continued to increase over time.

Detailed phenotyping of posterior vs. anterior circulation ischemic stroke: a multi-center MRI study

OBJECTIVE

Posterior circulation ischemic stroke (PCiS) constitutes 20-30% of ischemic stroke cases. Detailed information about differences between PCiS and anterior circulation ischemic stroke (ACiS) remains scarce. Such information might guide clinical decision making and prevention strategies. We studied risk factors and ischemic stroke subtypes in PCiS vs. ACiS and lesion location on magnetic resonance imaging (MRI) in PCiS.

METHODS

Out of 3,301 MRIs from 12 sites in the National Institute of Neurological Disorders and Stroke (NINDS) Stroke Genetics Network (SiGN), we included 2,381 cases with acute DWI lesions. The definition of ACiS or PCiS was based on lesion location. We compared the groups using Chi-squared and logistic regression.

RESULTS

PCiS occurred in 718 (30%) patients and ACiS in 1663 (70%). Diabetes and male sex were more common in PCiS vs. ACiS (diabetes 27% vs. 23%, p < 0.05; male sex 68% vs. 58%, p < 0.001). Both were independently associated with PCiS (diabetes, OR = 1.29; 95% CI 1.04-1.61; male sex, OR = 1.46; 95% CI 1.21-1.78). ACiS more commonly had large artery atherosclerosis (25% vs. 20%, p < 0.01) and cardioembolic mechanisms (17% vs. 11%, p < 0.001) compared to PCiS. Small artery occlusion was more common in PCiS vs. ACiS (20% vs. 14%, p < 0.001). Small artery occlusion accounted for 47% of solitary brainstem infarctions.

CONCLUSION

Ischemic stroke subtypes differ between the two phenotypes. Diabetes and male sex have a stronger association with PCiS than ACiS. Definitive MRI-based PCiS diagnosis aids etiological investigation and contributes additional insights into specific risk factors and mechanisms of injury in PCiS.

Is carotid imaging underused in patients with transient ischemic attack or ischemic stroke? A Swedish Stroke Register (Riksstroke) study

BACKGROUND AND AIM

Carotid artery stenosis is one of the major causes of transient ischemic attack (TIA) and acute ischemic stroke (IS), and carotid surgery and stenting are used to reduce the risk of ipsilateral IS. However, the adherence to the recommendation of carotid imaging in clinical practice has not been well studied. We analyzed proportions of carotid imaging and determinants for its non-use in patients with TIA and IS with respect to baseline demographics, risk factors, hospital characteristics, and geographical region.

PATIENTS AND METHODS

Hospital-based data on TIA and IS events, registered from July 2011 to June 2013, were obtained from the Swedish Stroke Register (Riksstroke). Carotid imaging diagnostics included carotid Doppler ultrasound and computed tomography angiography.

RESULTS

Carotid imaging was performed in 70% (10 545/15 021) of patients with TIA and 54% (23 772/44 075) of patients with IS. The most significant independent determinants for not undergoing carotid imaging were, in patients with TIA: age ≥85 year (odds ratio (OR), 7.3; 95% confidence interval (CI), 6.4-8.4) and a history of stroke (OR, 2.3; 95% CI, 2.1-2.5); and in patients with IS: age ≥85 year (OR, 9.8; 95% CI, 9.0-10.6), age 75-84 year (OR, 2.5; 95% CI, 2.3-2.7), and reduced level of consciousness at admission (OR, 3.4; 95% CI, 3.1-3.6). Care at a University hospital and in a stroke unit increased the likelihood of carotid imaging. There were substantial regional variations regarding proportions of carotid imaging.

CONCLUSION

Carotid imaging appears to be underused in patients with TIA and IS. Opportunities of secondary stroke prevention with carotid interventions are likely missed.

Transient ischemic attack and ischemic stroke patients with or without prior stroke

OBJECTIVES

A history of stroke is common in patients with transient ischemic attack (TIA) and ischemic stroke (IS), but there are few reports characterizing this group of patients. We aimed to compare characteristics, risk factors, and secondary preventive treatment in patients with TIA or IS with vs without a history of stroke.

METHODS

Hospital-based data on TIA and IS events, registered from July 2011 to June 2013, were obtained from the Swedish Stroke Register (Riksstroke). Previous stroke was not specified as hemorrhagic or ischemic.

RESULTS

A history of stroke was present in 19.3% (2892/15012) of TIA and 24.6% (10853/44169) of IS patients. Patients with prior stroke were older, more often male, and more likely to have atrial fibrillation (AF) (TIA: 27.4% vs 16.4%; IS: 36.1% vs 28.0%), hypertension (TIA: 77.5% vs 56.4%; IS: 74.2% vs 59.0%), and diabetes mellitus (TIA: 22.2% vs 14.2%; IS: 26.3% vs 19.5%) compared with those without (all differences P<.0001). At discharge, patients with prior stroke were more often treated with antihypertensive drugs than those without, whereas proportions treated with statins were similar in both groups. Patients with AF and prior stroke were less often treated with oral anticoagulant (OAC) medication than those without prior stroke.

CONCLUSIONS

Both in TIA and IS, vascular risk factors were more common in patients with a history of stroke compared with those without. In contrast to other secondary preventive medications, OAC treatment in the presence of AF was underutilized in patients with a history of stroke.

The influence of gravity on regional lung blood flow in humans: SPECT in the upright and head-down posture

Previous studies in humans have shown that gravity has little influence on the distribution of lung blood flow while changing posture from supine to prone. This study aimed to evaluate the maximal influence of posture by comparison of regional lung blood flow in the upright and head-down posture in 8 healthy volunteers, using a tilt table. Regional lung blood flow was marked by intravenous injection of macroaggregates of human albumin labeled with ^99mTc or ^113mIn, in the upright and head-down posture, respectively, during tidal breathing. Both radiotracers remain fixed in the lung after administration. The distribution of radioactivity was mapped using quantitative single photon emission computed tomography (SPECT) corrected for attenuation and scatter. All images were obtained supine during tidal breathing. A shift from upright to the head-down posture caused a clear redistribution of blood flow from basal to apical regions. We conclude that posture plays a role for the distribution of lung blood flow in upright humans, and that the influence of posture, and thereby gravity, is much greater in the upright and head-down posture than in horizontal postures. However, the results of the study demonstrate that lung structure is the main determinant of regional blood flow and gravity is a secondary contributor to the distribution of lung blood flow in the upright and head-down positions.NEW & NOTEWORTHY Using a dual-isotope quantitative SPECT method, we demonstrated that although a shift in posture redistributes blood flow in the direction of gravity, the results are also consistent with lung structure being a greater determinant of regional blood flow than gravity. To our knowledge, this is the first study to use modern imaging methods to quantify the shift in regional lung blood flow in humans at a change between the upright and head-down postures.

Standard dosing of piperacillin and meropenem fail to achieve adequate plasma concentrations in ICU patients

BACKGROUND

Controversies remain regarding optimal dosing and the need for plasma concentration measurements when treating intensive care patients with beta-lactam antibiotics.

METHODS

We studied ICU patients treated with either antibiotic, excluding patients on renal replacement therapy. Antibiotic concentrations were measured at the mid and end of the dosing interval, and repeated after 2-3 days when feasible. Glomerular filtration rate (GFR) was estimated from plasma creatinine and cystatin C, GFR calculated from cystatin C (eGFR) and measured creatinine clearance (CrCl). Measured concentrations were compared to the clinical susceptible breakpoints for Pseudomonas aeruginosa, 16 and 2 mg/l for piperacillin and meropenem respectively.

RESULTS

We analysed 33 and 31 paired samples from 20 and 19 patients treated with piperacillin-tazobactam and meropenem respectively. Antibiotic concentrations at the mid and end of the dosing interval were for piperacillin, 27.0 (14.7-52.9) and 8.6 (2.7-30.3); and for meropenem, 7.5 (4.7-10.2) and 2.4 (1.0-3.5). All values median (interquartile range) and concentrations in mg/l. The percentage of measured concentrations below the breakpoint at the mid and end of the dosing interval were for piperacillin, 27% and 61%; and for meropenem, 6% and 48%. Lower estimates of GFR were associated with higher concentrations but concentrations varied greatly between patients with similar GFR. The correlation with terminal concentration half-life was similar for eGFR and CrCl.

CONCLUSIONS

With standard doses of meropenem and piperacillin-tazobactam, plasma concentrations in ICU patients vary > 10-fold and are suboptimal in a significant percentage of patients. The variation is large also between patients with similar renal function.

Escalation to weekly dosing recaptures response in adalimumab-treated patients with moderately to severely active ulcerative colitis

BACKGROUND

Patients with moderately to severely active ulcerative colitis occasionally do not respond to or lose initial response to maintenance dosing of anti-TNF therapy.

AIM

To report the efficacy of escalation from every other week (EOW) to weekly adalimumab dosing in patients from the clinical trial ULTRA 2 (NCT00408629), by week 8 response (i.e. response after adalimumab induction therapy).

METHODS

Week 52 remission, response, and mucosal healing rates were assessed in ULTRA 2 adalimumab-randomised patients who escalated to weekly dosing. Patients were stratified by week 8 response per partial Mayo score. Kaplan-Meier and logistic regression analyses estimated time to weekly dosing and defined predictors of escalation to weekly dosing, respectively. Adverse events were reported for patients receiving open-label adalimumab.

RESULTS

The rate of escalation to weekly dosing was 16.3% (20/123) for week 8 responders and 38.4% (48/125) for week 8 nonresponders. Week 52 remission, response and mucosal healing rates with weekly dosing were 20%, 45%, and 45% for week 8 responders and 2.1%, 25% and 29.2% for nonresponders, respectively (NRI). The median time to weekly dosing was 288 days for week 8 nonresponders and not estimable for responders. Prior anti-TNF use was a significant predictor of escalation to weekly dosing. Treatment-emergent adverse event rates were similar for patients receiving open-label EOW or weekly adalimumab.

CONCLUSIONS

Escalation to weekly adalimumab dosing demonstrated clinical benefits for patients who lost response to therapy and may be beneficial for patients not initially responding to induction therapy. No new safety risks were identified with weekly dosing.

Time course analysis of mechanical ventilation-induced diaphragm contractile muscle dysfunction in the rat

Controlled mechanical ventilation (CMV) plays a key role in triggering the impaired diaphragm muscle function and the concomitant delayed weaning from the respirator in critically ill intensive care unit (ICU) patients. To date, experimental and clinical studies have primarily focused on early effects on the diaphragm by CMV, or at specific time points. To improve our understanding of the mechanisms underlying the impaired diaphragm muscle function in response to mechanical ventilation, we have performed time-resolved analyses between 6 h and 14 days using an experimental rat ICU model allowing detailed studies of the diaphragm in response to long-term CMV. A rapid and early decline in maximum muscle fibre force and preceding muscle fibre atrophy was observed in the diaphragm in response to CMV, resulting in an 85% reduction in residual diaphragm fibre function after 9-14 days of CMV. A modest loss of contractile proteins was observed and linked to an early activation of the ubiquitin proteasome pathway, myosin:actin ratios were not affected and the transcriptional regulation of myosin isoforms did not show any dramatic changes during the observation period. Furthermore, small angle X-ray diffraction analyses demonstrate that myosin can bind to actin in an ATP-dependent manner even after 9-14 days of exposure to CMV. Thus, quantitative changes in muscle fibre size and contractile proteins are not the dominating factors underlying the dramatic decline in diaphragm muscle function in response to CMV, in contrast to earlier observations in limb muscles. The observed early loss of subsarcolemmal neuronal nitric oxide synthase activity, onset of oxidative stress, intracellular lipid accumulation and post-translational protein modifications strongly argue for significant qualitative changes in contractile proteins causing the severely impaired residual function in diaphragm fibres after long-term mechanical ventilation. For the first time, the present study demonstrates novel changes in the diaphragm structure/function and underlying mechanisms at the gene, protein and cellular levels in response to CMV at a high temporal resolution ranging from 6 h to 14 days.

Dielectric Behaviour of the Ferroelectric AgNa(NO2)2 and Spin Lattice Relaxation of 23Na

The characteristic ferroelectric dispersion of the dielectric constant of AgNa(NO2)2 is measured near the ferroelectric phase transition. In accordance with other works an extremely slow relaxation is observed which can be related to a thermally activated motion of the electrical dipoles. The nuclear spin lattice relaxation time T1 of 23Na in AgNa(NO2)2 is measured by 90° - t-90° pulse sequences. In the entire temperature range the temperature dependence of T1 is governed by a thermally activated process which is ascribed to a diffusional motion. There is only a small influence of the dielectric instability on T1.

NMR Investigation of the Quadrupolar Glass Na(CN)xCl1-x

The freezing process of the CN dumbbells in the orientational glass Na(CN)xCl1-x was studied by 23Na and 35Cl NMR for several concentrations x. The systems with x ≳ 0.7 undergo structural phase transitions, whereas systems with x ≲ 0.7 stay cubic on the average down to lowest temperatures. For concentrations x ≈ 0.65, the temperature dependences of the NMR line widths give evidence that the transition into the glass state essentially consists in a deformation of the local potential leading to a formation of preferential directions for the orientations of the CN ions. The temperature dependence of the spin lattice relaxation time T, shows that the motion of the CN ions in their deformed potentials remain fast. With decreasing concentration x, the influence of the collective interactions between the CN ions become less pronounced and a gradual transition to systems with decoupled CN ions can be observed.

Regional lung ventilation in humans during hypergravity studied with quantitative SPECT

Recently we challenged the view that arterial desaturation during hypergravity is caused by redistribution of blood flow to dependent lung regions by demonstrating a paradoxical redistribution of blood flow towards non-dependent regions. We have now quantified regional ventilation in 10 healthy supine volunteers at normal and three times normal gravity (1G and 3G). Regional ventilation was measured with Technegas ((99m)Tc) and quantitative single photon emission computed tomography (SPECT). Hypergravity caused arterial desaturation, mean decrease 8%, p<0.05 vs. 1G. The ratio for mean ventilation per voxel for non-dependent and dependent lung regions was 0.81±0.12 during 1G and 1.63±0.35 during 3G (mean±SD), p<0.0001. Thus, regional ventilation was shifted from dependent to non-dependent regions. We suggest that arterial desaturation during hypergravity is caused by quantitatively different redistributions of blood flow and ventilation. To our knowledge, this is the first study presenting high-resolution measurements of regional ventilation in humans breathing normally during hypergravity.

High incidence of post-injury pneumonia in intensive care-treated trauma patients

INTRODUCTION

Trauma patients are susceptible to post-injury infections. We investigated the incidence, as well as risk factors for development of pneumonia in intensive care unit (ICU)-treated trauma patients. In addition, we report pathogens identified in patients that developed pneumonia.

METHODS

The study cohort consisted of 322 trauma patients admitted to the ICU at a level-one trauma centre following initial resuscitation. Patients 15 years or older with an ICU stay of more than 24 h were included. We investigated pre-hospital and hospital parameters during the first 24 h after admission and their possible association with pneumonia within 10 days of ICU admission.

RESULTS

Majority of the patients were male (78%) and the median age was 41 years. The overall degree of injury was high with a median Injury Severity Score (ISS) of 24. Overall 30-day mortality was 9%. Eighty-five (26%) patients developed pneumonia during their first 10 days in the ICU. Univariate logistic regression revealed that intubation in the field, shock, Glasgow Coma Scale (GCS) 3-8, major surgery within 24 h after admission, massive transfusion and ISS > 24 were all risk factors for subsequent development of pneumonia. In the multivariable model, only GCS 3-8 was identified as an independent risk factor. In 42 out of the 85 cases of pneumonia, the diagnosis was defined by significant growth of at least one pathogen where Enterobacteriaceae and Staphylococcus aureus were the most common.

CONCLUSIONS

Pneumonia is a common complication among ICU-treated trauma patients. Reduced consciousness is an independent risk factor for development of pneumonia after severe injury.

Feasibility of endovascular and surface cooling strategies in acute stroke

BACKGROUND

Therapeutic hypothermia (TH) is a promising treatment of stroke, but limited data are available regarding the safety and effectiveness of cooling methodology. We investigated the safety of TH and compared the cooling capacity of two widely used cooling strategies - endovascular and surface cooling.

METHODS

COOLAID Oresund is a bicentre randomized trial in Copenhagen (Denmark) and Malmö (Sweden). Patients were randomized to either TH (33°C for 24 h) in a general intensive care unit (ICU) or standardized stroke unit care (control). Cooling was induced by a surface or endovascular-based strategy.

RESULTS

Thirty-one patients were randomized. Seven were cooled using endovascular and 10 using surface-based cooling methods and 14 patients received standard care (controls). 14 (45%) patients received thrombolysis. Pneumonia was recorded in 6 (35%) TH patients and in 1 (7%) control. 4 TH patients and 1 control developed massive infarction. 1 TH patient and 2 control suffered asymptomatic haemorrhagic transformation. Mortality was comparable with 2 (12%) in the TH group and 1 (7%) among controls. Mean (SD) duration of hospital stay was 25.0 days (24, 9) in TH and 22.5 days (20.6) in control patients (P = 0.767). Mean (SD) induction period (cooling onset to target temperature) was 126.3 min (80.6) with endovascular cooling and 196.3 min (76.3) with surface cooling (P = 0.025).

CONCLUSIONS

Therapeutic hypothermia with general anaesthesia is feasible in stroke patients. We noticed increased rates of pneumonia, while the length of hospital stay remained comparable. The endovascular cooling strategy provides a faster induction period than surface cooling.

Importance and regulation of the colonic mucus barrier in a mouse model of colitis

The colonic mucus layer serves as an important barrier and prevents colonic bacteria from invading the mucosa and cause inflammation. The regulation of colonic mucus secretion is poorly understood. The aim of this study was to investigate the role of the mucus barrier in induction of colitis. Furthermore, regulation of mucus secretion by luminal bacterial products was studied. The colon of anesthetized Muc2(-/-), Muc1(-/-), wild-type (wt), and germ-free mice was exteriorized, the mucosal surface was visualized, and mucus thickness was measured with micropipettes. Colitis was induced by DSS (dextran sodium sulfate, 3%, in drinking water), and disease activity index (DAI) was assessed daily. The colonic mucosa of germ-free and conventionally housed mice was exposed to the bacterial products LPS (lipopolysaccharide) and PGN (peptidoglycan). After DSS induction of colitis, the thickness of the firmly adherent mucus layer was significantly thinner after 5 days and onward, which paralleled the increment of DAI. Muc2(-/-) mice, which lacked firmly adherent mucus, were predisposed to colitis, whereas Muc1(-/-) mice were protected with significantly lower DAI by DSS compared with wt mice. The mucus barrier increased in Muc1(-/-) mice in response to DSS, whereas significantly fewer T cells were recruited to the inflamed colon. Mice housed under germ-free conditions had an extremely thin adherent colonic mucus layer, but when exposed to bacterial products (PGN or LPS) the thickness of the adherent mucus layer was quickly restored to levels observed in conventionally housed mice. This study demonstrates a correlation between decreasing mucus barrier and increasing clinical symptoms during onset of colitis. Mice lacking colonic mucus (Muc2(-/-)) were hypersensitive to DSS-induced colitis, whereas Muc1(-/-) were protected, probably through the ability to increase the mucus barrier but also by decreased T cell recruitment to the afflicted site. Furthermore, the ability of bacteria to regulate the thickness of the colonic mucus was demonstrated.

Hyperdense middle cerebral artery sign is an ominous prognostic marker despite optimal workflow

OBJECTIVES

To evaluate the association between the hyperdense middle cerebral artery sign (HMCAS) and the functional outcome on one hand, and different predictors such as the National Institutes of Health Stroke Scale (NIHSS), infarct size, ASPECTS Score, intracerebral hemorrhage, and mortality on the other hand.

MATERIAL AND METHODS

Retrospective analysis of 120 patients with MCA-stroke treated with intravenous thrombolysis. We tested the association between HMCAS and NIHSS, infarct volume, ASPECTS, outcome, level of consciousness, different recorded time intervals, and the day/time of admission.

RESULTS

Seventy-four percentage of patients treated with thrombolysis developed cerebral infarction. All patients with HMCAS (n = 39) sustained infarction and only 31% showed favorable outcome compared with 62% and 60%, respectively among patients without HMCAS (P < 0.001 and P = 0.002). There was statistically significant association between functional outcome and HMCAS (P = 0.002), infarct volume, NIHSS, and ASPECTS (P < 0.001). The time to treatment was 12 min shorter in patients who developed infarction (P = 0.037). Independent predictors for outcome were NIHSS and the occurrence of cerebral infarction on computed tomography for the whole study population, and infarct volume for patients who sustained cerebral infarction.

CONCLUSIONS

Despite optimal workflow, patients with HMCAS showed poor outcome after intravenous thrombolysis. The results emphasize the urgent need for more effective revascularization therapies and neuroprotective treatment in this subgroup of stroke patients.

Sural nerve biopsy may predict future nerve dysfunction

OBJECTIVE

Sural nerve pathology in peripheral neuropathy shows correlation with clinical findings and neurophysiological tests. The aim was to investigate progression of nerve dysfunction over time in relation to a baseline nerve biopsy.

METHODS

Baseline myelinated nerve fiber density (MNFD) was assessed in sural nerve biopsies from 10 men with type 2 diabetes, 10 with impaired and 10 with normal glucose tolerance. Nerve conduction and quantitative perception thresholds were estimated at baseline and follow-up (7-10 years later).

RESULTS

Subjects with low MNFD (< or = 4700 fibers/mm(2)) showed decline of peroneal amplitude (P < 0.02) and conduction velocity (P < 0.04), as well as median nerve sensory amplitude (P < 0.05) and motor conduction velocity (P < 0.04) from baseline to follow-up. In linear regression analyses, diabetes influenced decline of nerve conduction. MNFD correlated negatively with body mass index (r = -0.469; P < 0.02).

CONCLUSION

Low MNFD may predict progression of neurophysiological dysfunction and links obesity to myelinated nerve fiber loss.

Lactobacillus reuteri prevents colitis by reducing P-selectin-associated leukocyte- and platelet-endothelial cell interactions

Recent findings indicate that dextran sodium sulfate (DSS)-induced colitis is associated with a prothrombogenic phenotype, with P-selectin playing a major role in platelet recruitment. It has been suggested that probiotics may ameliorate colonic inflammation. We therefore investigated how treatment with Lactobacillus reuteri influenced P-selectin expression, leukocyte and platelet endothelial cell interactions, and colitis severity in DSS-treated rats. Rats were divided into the following four groups: nontreated, DSS treated (5% in drinking water for 9 days), L. reuteri, and L. reuteri and DSS treated. The rats were anesthetized with Inactin (120 mg/kg ip), and the dual radiolabeled monoclonal antibody technique was used to quantify P-selectin expression. Leukocyte-endothelial and platelet-endothelial cell interactions were studied in colonic venules with intravital microscopy. Colitis severity was assessed using a disease activity index. Disease activity index increased, as did the expression of P-selectin in the entire colon after DSS treatment, but both were reduced to control levels with L. reuteri pretreatment. The increased platelet- and leukocyte-endothelial cell interactions after DSS treatment were abolished by pretreatment with L. reuteri. L. reuteri protects against DSS-induced colitis in rats. The protection is associated with reduced P-selectin expression and a decrease in leukocyte- and platelet-endothelial cell interactions.

Process of foregoing life-sustaining treatment: a survey among Scandinavian intensivists

BACKGROUND

How ethical issues are dealt with varies considerably depending on the geographic and religious background of individuals. The views of Scandinavian physicians on end-of-life care were studied using a survey. The aim of this study was to clarify the actual processes of foregoing life-sustaining treatment in Scandinavia.

METHODS

A questionnaire was developed and sent to 78 intensive care physicians working in Denmark, Finland, Norway and Sweden.

RESULTS

Forty-four responses were obtained (13 from Denmark, eight from Finland, 12 from Norway and 11 from Sweden); 89% of the respondents were from University Hospitals. Withholding and withdrawing of treatment were practiced in all intensive care units (ICUs) concerned, but written guidelines on end-of-life care existed in only one ICU. End-of-life care is usually arranged in the ICU. Religious support is available in most hospitals during office hours, but lacking in 26% of ICUs outside office hours. Vasoactive medication, renal replacement therapy, and artificial nutrition are among the therapies most likely to be discontinued during withdrawal of life support. Certain types of monitoring and organ support are still continued in many centers during end-of-life care.

CONCLUSION

Local written guidelines on end-of-life care are scarce in Scandinavian ICUs, which may explain the observed variability in the practices. Development of guidelines and monitoring how these instructions are carried out may help to improve the quality of care of dying ICU patients.

Risk factors and treatment at recurrent stroke onset: results from the Recurrent Stroke Quality and Epidemiology (RESQUE) Study

BACKGROUND

Much effort has been made to study first-ever stroke patients. However, recurrent stroke has not been investigated as extensively. It is unclear which risk factors dominate, and whether adequate secondary prevention has been provided to patients who suffer from recurrent stroke. Also, the different types of recurrent stroke need further evaluation.

METHODS

The study included patients with recurrent stroke admitted to twenty-three Swedish stroke centers. The type of previous and recurrent stroke was determined, as well as evaluation (when applicable) of recurrent ischemic stroke according to the TOAST classification. Presence of vascular risk factors was registered and compared to the type of stroke. Also assessed was ongoing secondary prevention treatment at recurrent stroke onset.

RESULTS

A total of 889 patients with recurrent stroke (mean age 77) were included in the study. Of these, 805 (91%) had ischemic stroke, 78 (9%) had intracerebral hemorrhage and 6 (<1%) stroke of unknown origin. The most frequent vascular risk factors were hypertension (75%) and hyperlipidemia (56%). Among the 889 patients, 29% had atrial fibrillation. Of the patients in the ischemic group with cardiac embolism, only 21% were on anticoagulation treatment. The majority of the patients (75%) had their most recent previous stroke >12 months before admission.

CONCLUSIONS

Few patients had a recurrent stroke shortly after the previous stroke in this study. This indicates that it is meaningful to prevent a second event with an adequate long-term treatment strategy for secondary prevention after first-ever stroke. There also seems to be a clear potential for improving secondary prevention after stroke.

Impaired platelet function correlates with multi-organ dysfunction. A study of patients with sepsis

Patients with sepsis often suffer from haemostatic disturbances such as haemorrhage and disseminated intravascular coagulation (DIC). Considering the pivotal role of platelets in haemostasis, we have investigated platelet function by flow cytometry in 16 patients with sepsis for a better understanding of their haemostatic function. We have also investigated whether platelet function correlates with the severity of disease assessed by multiple organ dysfunction (MOD) score and patient outcome. The platelet response ex vivo after stimulation with agonists, measured as platelet fibrinogen, binding was low in comparison with healthy volunteers ( n = 30). This could reflect a previous response to agonists in vivo , which lead to platelet activation and consumption and formation of microthrombi that could then participate in the development of M OD. The platelets that remain in the circulation might be the result of a selection process where the most active platelets have already been consumed, and the remaining population consists of less active platelets. Another explanation might be desensitization of the remaining platelets because of exposure to agonists in vivo . Platelet activation with the agonists ADP and arachidonic acid were predictive of subsequent development of MOD and final patient outcome.

Ethical issues in intensive care--a survey among Scandinavian intensivists

BACKGROUND

The general principles of medical ethics are universally accepted. In practice, however, there is variation on how these principles are interpreted by people with different cultural backgrounds. The aim of this study was to document the views of Scandinavian intensive care physicians on intensive care unit (ICU) admission, triage, withholding and withdrawal of intensive care, and communication between the patient, the family and the ICU team.

METHODS

A questionnaire was developed and sent to 84 intensive care physicians working in Denmark, Finland, Sweden and Norway.

RESULTS

The response rate was 61%. In general, the responses were in agreement with published guidelines. Nevertheless, there was considerable variation on what factors are taken into account when priority decisions are made. In addition, the views on the content of information provided to the family varied. A majority of 80% reported priority decisions being made on a regular basis. Less than one-half of the respondents had correct knowledge regarding the existence or lack of national guidelines on intensive care ethics. Only 8% of the respondents were aware of guidelines published by the Society of Critical Care Medicine.

CONCLUSION

Variation in priority determinants between individual physicians may compromise justice in health care. An effort should be made to discuss and adopt mutual principles. In addition, the quality of information available to the patients' representatives deserves our attention. The results of this study could be used as a basis for discussion when guidelines on the ethical aspects of intensive care are developed and reviewed.

An in vivo model for gastric physiological and pathophysiological studies in the mouse

AIM

In vivo models for studying gastrointestinal physiology and pathophysiology are well established in rats. Since a number of genetically modified mice are available there is a need for reliable mouse models. The aim of this project was to develop an in vivo mouse model for gastrointestinal studies.

METHODS

C57bl/6, NMRI and transgenic FVB/N (expressing human alpha-1,3/4-fucosyltransferase) mice were anaesthetized with isoflurane and the gastric mucosa exteriorized for intravital microscopy. Acid-base status and acid secretion were measured and blood pressure was continuously monitored. Gastric mucosal blood flow was recorded by laser-Doppler flowmetry. Mucus thickness and accumulation rate were measured with micropipettes.

RESULTS

We have developed an in vivo mouse model for studies of the gastric mucosa. With isoflurane anaesthesia the preparation can be studied for up to 5 h with stable blood pressure and mucosal blood flow. Acid-base status agrees with results from other laboratories. Blood flow increased in both C57bl/6 and alpha1.3/4-FT mice in response to luminal HCl, and the mucus gel could be divided into a firmly and a loosely adherent layer, all comparable with results in the rat. However, the firmly adherent mucus layer was thinner (45 +/- 2 microm), and the mucus accumulation rate lower, than in the rat. Furthermore, both basal and stimulated acid secretion showed lower outputs than in the rat.

CONCLUSIONS

This model has great potential for investigations of gastrointestinal physiology and pathophysiology and can be applied for Helicobacter pylori infection studies.

Distributions of lung ventilation and perfusion in prone and supine humans exposed to hypergravity

When normal subjects are exposed to hypergravity [5 times normal gravity (5 G)] there is an impaired arterial oxygenation that is less severe in the prone compared with supine posture. We hypothesized that under these conditions the heterogeneities of ventilation and/or perfusion distributions would be less prominent when subjects were prone compared with supine. Expirograms from a combined rebreathing-single breath washout maneuver (Rohdin M, Sundblad P, and Linnarsson D. J Appl Physiol 96: 1470–1477, 2004) were analyzed for vital capacity (VC), phase III slope, and phase IV amplitude, to analyze heterogeneities in ventilation (Ar) and perfusion [CO2-to-Ar ratio (CO2/Ar)] distribution, respectively. During hypergravity, VC decreased more in the supine than in the prone position (ANOVA, P = 0.02). Phase III slope was more positive for Ar ( P = 0.003) and more negative for CO2/Ar ( P = 0.007) in the supine compared with prone posture at 5 G, in agreement with the notion of a more severe hypergravity-induced ventilation-perfusion mismatch in supine posture. Phase IV amplitude became lower in the supine than in the prone posture for both Ar ( P = 0.02) and CO2/Ar ( P = 0.004) during hypergravity as a result of the more reduced VC in the supine posture. We speculate that results of VC and phase IV amplitude are due to the differences in heart-lung interaction and diaphragm position between postures: a stable position of the heart and diaphragm in prone hypergravity, in contrast to supine in which the weight of the heart and a cephalad shift of the diaphragm compress lung tissue.

Effects of gravity on lung diffusing capacity and cardiac output in prone and supine humans

Both in normal subjects exposed to hypergravity and in patients with acute respiratory distress syndrome, there are increased hydrostatic pressure gradients down the lung. Also, both conditions show an impaired arterial oxygenation, which is less severe in the prone than in the supine posture. The aim of this study was to use hypergravity to further investigate the mechanisms behind the differences in arterial oxygenation between the prone and the supine posture. Ten healthy subjects were studied in a human centrifuge while exposed to 1 and 5 times normal gravity (1 G, 5 G) in the anterioposterior (supine) and posterioanterior (prone) direction. They performed one rebreathing maneuver after approximately 5 min at each G level and posture. Lung diffusing capacity decreased in hypergravity compared with 1 G (ANOVA, P = 0.002); it decreased by 46% in the supine posture compared with 25% in the prone (P = 0.01 for supine vs. prone). At the same time, functional residual capacity decreased by 33 and 23%, respectively (P < 0.001 for supine vs. prone), and cardiac output by 40 and 31% (P = 0.007 for supine vs. prone), despite an increase in heart rate of 16 and 28% (P < 0.001 for supine vs. prone), respectively. The finding of a more impaired diffusing capacity in the supine posture compared with the prone at 5 G supports our previous observations of more severe arterial hypoxemia in the supine posture during hypergravity. A reduced pulmonary-capillary blood flow and a reduced estimated alveolar volume can explain most of the reduction in diffusing capacity when supine.

Protective effect of prone posture against hypergravity-induced arterial hypoxaemia in humans

Patients with acute respiratory distress syndrome have increased lung tissue weight and therefore an increased hydrostatic pressure gradient down the lung. Also, they have a better arterial oxygenation in prone (face down) than in supine (face up) posture. We hypothesized that this effect of the direction of gravity also existed in healthy humans, when increased hydrostatic gradients were induced by hypergravity. Ten healthy subjects were studied in a human centrifuge while exposed to 1 or 5 G in anterio-posterior (supine) or posterio-anterior (prone) direction. We measured blood gases using remote-controlled sampling and gas exchange by mass spectrometry. Hypergravity led to marked impairments of arterial oxygenation in both postures and more so in supine posture. At 5 G, the arterial oxygen saturation was 84.6 +/- 1.2 % (mean +/- S.E.M.) in supine and 89.7 +/- 1.4 % in prone posture (P < 0.001 for supine vs. prone). Ventilation and alveolar PO2 were increased at 5 G and did not differ between postures. The alveolar-to-arterial PO2 difference increased at 5 G to 8.0 +/- 0.2 kPa and 6.6 +/- 0.3 kPa in supine and prone postures (P = 0.003). Arterial oxygenation was less impaired in prone during hypergravity due to a better-preserved alveolo-arterial oxygen transport. We speculate that mammals have developed a cardiopulmonary structure that favours function with the gravitational vector in the posterio-anterior direction.

The influence of formulation variables on the properties of pellets containing a self-emulsifying mixture

A method of converting self-emulsifying drug delivery systems to a pellet form has been studied. Formulations with varied relative quantities of an oil/surfactant mixture, water, microcrystalline cellulose (MCC), and lactose were chosen in a statistical design after preliminary ranging experiments. Pellets were produced by extrusion/spheronization. The characteristics of the pellets were studied by sieving, disintegration testing, diametral compression, image analysis, non-contact laser profilometry, and scanning electron microscopy. The effects of the formulation variables on pellet properties were evaluated by analysis of variance. It was possible to relate the formulation variables to all the quantified pellet properties except the shape. The relative quantities of oil/surfactant and water had an effect on the amount of liquid and oil/surfactant that could be incorporated into the powder, extrusion force, median diameter, size spread, disintegration time, tensile strength, and surface roughness. The relative quantities of lactose and MCC had an effect on the amount of liquid and oil/surfactant that could be incorporated into the powder, tensile strength, and roughness only. Water was an essential element of the formulations. The maximum quantity of the specific oil/surfactant combination studied that can be incorporated was 42% of the dry pellet weight.

Vasodilator effects of KRN2391, levcromakalim and 3-morpholino-sydnonimin in human pial and omental arteries

The vasodilator action of KRN2391 (10 nM-10 microM), a combined ATP-sensitive potassium channel (KATP) opener and organic nitrate, was investigated in human pial and omental arteries. Previous animal studies have suggested that opening of KATP and activation of guanylate cyclase may contribute to varying extents to the vasodilator action of KRN2391, depending on the origin and size of the vascular preparation. Vasodilator responses were studied in isolated vascular segments (diameter 0.4-0.8 mm) pre-contracted with endothelin-1 in the presence or absence of glibenclamide (inhibitor of KATP), LY83583 (inhibitor of guanylate cyclase), zaprinast (inhibitor of cyclic GMP phosphodiesterase V) and NG-nitro-L-arginine (inhibitor of nitric oxide synthase). KRN2391 induced concentration-dependent vasodilator responses of similar potency in arteries from the two vascular regions. While glibenclamide (1 microM) had no effect in omental arteries, this compound produced a tenfold rightwards shift of the concentration-response curve for KRN2391 in pial arteries without affecting the maximal response (Emax). LY83583 (10 microM), zaprinast (10 microM) and NG-nitro-L-arginine (0.1 mM) all failed to affect the vasodilator responses to KRN2391 significantly in either artery. However, in ring segments of rat aorta LY83583 displaced the concentration-response curve for the nitric oxide donor 3-morpholino-sydnonimin (10 nM-0.1 mM) to the right, while zaprinast produced a leftwards shift. The prototype KATP opener levcromakalim (0.01-10 microM) elicited a larger relaxation in pial (Emax 80+/-6%) than in omental (Emax 47+/-13%) arteries, whereas 3-morpholino-sydnonimin produced a smaller relaxation in pial (Emax 50+/-18%) than in omental (Emax 90+/-4%) arteries. These results suggest that the vasodilator response to KRN2391 is mediated by KATP in human cerebral arteries, but dependent on neither KATP nor guanylate cyclase in human omental arteries. The results with levcromakalim and 3-morpholino-sydnonimin indicate that opening of KATP may be a more effective mechanism of vasodilatation in pial than in omental arteries from man, whereas the reverse appears to be true for guanylate cyclase activation.

Differential actions of anandamide, potassium ions and endothelium-derived hyperpolarizing factor in guinea-pig basilar artery

Vasodilator responses to anandamide (arachidonylethanolamide) and potassium ions were compared with those mediated by endothelium-derived hyperpolarizing factor (EDHF) in guinea-pig isolated basilar artery contracted with prostaglandin F2alpha. In this artery, EDHF-mediated responses can be evoked by acetylcholine in the presence of both indomethacin (10 microM) and NG-nitro-L-arginine (0.3 mM). In endothelium-denuded arterial segments, which failed to respond to acetylcholine, anandamide was still able to evoke a complete relaxation. Anandamide (10 microM) did not affect the resting membrane potential, whereas acetylcholine (10 microM) hyperpolarized the smooth muscle cells by 23 mV in the presence of indomethacin and NG-nitro-L-arginine. Pre-treatment with capsaicin (10 microM) or resiniferatoxin (0.1 microM) abolished the anandamide-induced relaxation, but had no effect on the EDHF-mediated relaxation induced by acetylcholine. Treatment with a mixture of the calcium-sensitive potassium channel inhibitors, apamin and charybdotoxin, which abolishes EDHF-mediated relaxation in this artery, did not affect the relaxation evoked by anandamide. The additional presence of glibenclamide or ciclazindol, inhibitors of ATP-sensitive and voltage-dependent potassium channels, also had no effect on the anandamide-induced relaxation. Increasing the potassium ion concentration by 2-10 mM induced inconsistent vasodilator responses. However, re-admission of potassium ions to preparations incubated in potassium-free solution elicited almost complete and sustained relaxations. A short incubation period with ouabain (10 microM for 10 min) or cooling (18-22 degrees C) abolished these responses, whereas the acetylcholine-induced relaxation in the presence of indomethacin and NG-nitro-L-arginine was unaffected (ouabain) or partially reduced (cooling). The anandamide-induced relaxation was also abolished by ouabain and cooling. Furthermore, ouabain inhibited the vasodilator response to capsaicin, but not that to calcitonin gene-related peptide (CGRP), and per se evoked a release of CGRP from the artery. The gap junction uncoupler, 18alpha-glycyrrhetinic acid (100 microM), affected neither the EDHF-mediated relaxation induced by acetylcholine nor the vasodilator responses to anandamide and potassium ions. Thus, EDHF-mediated vasorelaxation in the guinea-pig basilar artery does not seem to involve Na+/K+-ATPase, sensory nerves or gap junctions. These results indicate that EDHF is neither anandamide nor potassium ions in this artery.

Intracellular localization of an active green fluorescent protein-tagged Pho84 phosphate permease in Saccharomyces cerevisiae

Green fluorescent protein (GFP) from Aequorea victoria was used as an in vivo reporter protein when fused to the carboxy-terminus of the Pho84 phosphate permease of Saccharomyces cerevisiae. Both components of the fusion protein displayed their native functions and revealed a cellular localization and degradation of the Pho84-GFP chimera consistent with the behavior of the wild-type Pho84 protein. The GFP-tagged chimera allowed for a detection of conditions under which the Pho84 transporter is localized to its functional environment, i.e. the plasma membrane, and conditions linked to relocation of the protein to the vacuole for degradation. By use of the methodology described, GFP should be useful in studies of localization and degradation also of other membrane proteins in vivo.

Quality of life among early retirees

Explanatory variables concerning poor quality of life (QL) were established among disability pensioners with musculoskeletal disorders and a control group. In both groups health status, leisure time activities, and social network were important for QL. Among the retirees immigration, employment before retirement and a negative attitude to the disability pension were related to poor QL.

Vasodilator action in the nitroxylated cyanoamidine derivative, KRN2391, in rabbit basilar artery

KRN2391 is a cyanoamidine derivative with a pyridine ring and a nitroxyl group. This gives the molecule a dual pharmacological action as both an ATP-sensitive K channel (K(ATP)) opener and an organic nitrate. In cerebrovascular disease with endothelial dysfunction, such a compound could be advantageous to prevent the negative consequences of a reduced synthesis of endogenous nitric oxide and endothelium-derived hyperpolarizing factor. The objective of this study was to characterise the vasodilator action of KRN2391 in a cerebral artery. As shown in the rabbit basilar artery contracted by endothelin-1 KRN2391 elicited a concentration-dependent relaxation. KRN2391 was unable to relax arteries contracted by a 60 mM K solution. The KRN2391-induced relaxation of endothelin-1-contracted arteries was unaffected by N(G)-nitro-L-arginine (0.1 mM), indomethacin (10 microM) or removal of the endothelium. The guanylate cyclase inhibitors ODQ (10 microM) and LY53583 (10 microM), and the cGMP phosphodiesterase inhibitor zaprinast (10 microM) each had no effect on the KRN2391-induced relaxation. Glibenclamide (1 microM), a blocker of K(ATP), caused a rightward shift of the concentration-response curve for KRN2391. The relaxation induced by the prototype K(ATP) opener levcromakalim was inhibited to a similar extent by glibenclamide. Addition of ODQ or LY53583, or the calcium-sensitive K channel blockers apamin (0.1 microM) and charybdotoxin (0.1 microM) in the presence of glibenclamide did not produce a significant further inhibition of the KRN-induced relaxation. KRN2391 (10 microM) did not influence the content of cGMP in the basilar artery, whereas the nitric oxide donor 3-morpholino-sydnonimine (0.1 mM) increased the cGMP level three-fold. Thus, KRN2391 is an effective vasodilator of the rabbit basilar artery, acting mainly through opening of KATP . The nitro-moiety of the molecule does not seem to contribute to the relaxant effect in this artery.

Vanilloid receptors on sensory nerves mediate the vasodilator action of anandamide

The endogenous cannabinoid receptor agonist anandamide is a powerful vasodilator of isolated vascular preparations, but its mechanism of action is unclear. Here we show that the vasodilator response to anandamide in isolated arteries is capsaicin-sensitive and accompanied by release of calcitonin-gene-related peptide (CGRP). The selective CGRP-receptor antagonist 8-37 CGRP, but not the cannabinoid CB1 receptor blocker SR141716A, inhibited the vasodilator effect of anandamide. Other endogenous (2-arachidonylglycerol, palmitylethanolamide) and synthetic (HU 210, WIN 55,212-2, CP 55,940) CB1 and CB2 receptor agonists could not mimic the action of anandamide. The selective 'vanilloid receptor' antagonist capsazepine inhibited anandamide-induced vasodilation and release of CGRP. In patch-clamp experiments on cells expressing the cloned vanilloid receptor (VR1), anandamide induced a capsazepine-sensitive current in whole cells and isolated membrane patches. Our results indicate that anandamide induces vasodilation by activating vanilloid receptors on perivascular sensory nerves and causing release of CGRP. The vanilloid receptor may thus be another molecular target for endogenous anandamide, besides cannabinoid receptors, in the nervous and cardiovascular systems.

Characterization of endothelium- dependent relaxation in guinea pig basilar artery - effect of hypoxia and role of cytochrome P450 mono-oxygenase

In the guinea pig basilar artery, acetylcholine and the calcium ionophore A23187 induced endothelium-dependent relaxations, which were not significantly affected by the nitric oxide (NO) synthase inhibitor Nomega-nitro-L-arginine (L-NOARG; 0.3 mM) or the guanylate cyclase inhibitor ODQ (1H-[1,2,4]oxadiazolo[4,3-a]quinoxaline-1-one; 1-10 microM), or by these inhibitors combined. However, acetylcholine (10 microM) and A23187 (3 microM) each significantly increased the tissue level of cGMP in the absence but not in the presence of L-NOARG, suggesting that NO is released from the vascular endothelium in this blood vessel. Treatment with the potassium (K) channel inhibitors charybdotoxin (0.1 microM) plus apamin (0.1 microM), a toxin mixture previously shown to inhibit relaxations mediated by endothelium-derived hyperpolarizing factor (EDHF) in this artery, had no effect on the A23187-induced relaxation but slightly inhibited the response to acetylcholine (Emax was reduced by 24%). When the action of EDHF was prevented by these K channel inhibitors, the remaining relaxation was abolished by either ODQ (1 microM) or L-NOARG (0.3 mM), indicating that NO, apart from EDHF, contributes to the endothelium-dependent relaxations. Furthermore, ODQ (10 microM) abolished the relaxation induced by the NO donor S-nitroso-N-acetylpenicillamine. Thus, activation of soluble guanylate cyclase seems to be the only mechanism through which NO causes relaxation in this artery. When vessels were exposed to grave hypoxia (pO2 = 6 mm Hg), the NO-mediated relaxation (induced by acetylcholine in the presence of charybdotoxin plus apamin) disappeared. In contrast, EDHF-mediated responses (elicited by acetylcholine in the presence of L-NOARG) were only marginally affected by hypoxia (Emax was reduced by 16%). 17-Octadecynoic acid (50 microM) and 5,8,11,14-eicosatetraynoic acid (10 microM), inhibitors of cytochrome P450-dependent oxidation of arachidonic acid, failed to inhibit the acetylcholine-induced relaxation in the presence of L-NOARG. The cytochrome P450-dependent arachidonic acid metabolite 11,12-epoxyecosatrienoic acid (0.3-3.0 microM) had no relaxant effect per se. In conclusion, EDHF and NO are both mediators of endothelium-dependent relaxations in the guinea pig basilar artery. However, during grave hypoxia, EDHF alone mediates acetylcholine-induced relaxation. The results further suggest that EDHF is not a metabolite of arachidonic acid formed by cytochrome P450 mono-oxygenase or generated by another oxygen-dependent enzyme in this artery.

Phosphate permeases of Saccharomyces cerevisiae

The PHO84 and PHO89 genes of Saccharomyces cerevisiae encode two high-affinity phosphate cotransporters of the plasma membrane. Hydropathy analysis suggests a secondary structure arrangements of the proteins in 12 transmembrane domains. The derepressible Pho84 and Pho89 transporters appear to have characteristic similarities with the phosphate transporters of Neurospora crassa. The Pho84 protein catalyzes a proton-coupled phosphate transport at acidic pH, while the Pho89 protein catalyzes a sodium-dependent phosphate uptake at alkaline pH. The Pho84 transporter can be stably overproduced in the cytoplasmic membrane of Escherichia coli, purified and reconstituted in a functional state into proteoliposomes.

Characterization of the potassium channels involved in EDHF-mediated relaxation in cerebral arteries

1. In the presence of NG-nitro-L-arginine (L-NOARG, 0.3 mM) and indomethacin (10 microM), the relaxations induced by acetylcholine and the calcium (Ca) ionophore A23187 are considered to be mediated by endothelium-derived hyperpolarizing factor (EDHF) in the guinea-pig basilar artery. 2. Inhibitors of adenosine 5'-triphosphate (ATP)-sensitive potassium (K)-channels (KATP; glibenclamide, 10 microM), voltage-sensitive K-channels (Kv; dendrotoxin-1, 0.1 microM or 4-aminopyridine, 1 mM), small (SKCa; apamin, 0.1 microM) and large (BKCa; iberiotoxin, 0.1 microM) conductance Ca-sensitive K-channels did not affect the L-NOARG/indomethacin-resistant relaxation induced by acetylcholine. 3. Synthetic charybdotoxin (0.1 microM), an inhibitor of BKCa and Kv, caused a rightward shift of the concentration-response curve for acetylcholine and reduced the maximal relaxation in the presence of L-NOARG and indomethacin, whereas the relaxation induced by A23187 was not significantly inhibited. 4. A combination of charybdotoxin (0.1 microM) and apamin (0.1 microM) abolished the L-NOARG/ indomethacin-resistant relaxations induced by acetylcholine and A23187. However, the acetylcholine-induced relaxation was not affected by a combination of iberiotoxin (0.1 microM) and apamin (0.1 microM). 5. Ciclazindol (10 microM), an inhibitor of Kv in rat portal vein smooth muscle, inhibited the L-NOARG/ indomethacin-resistant relaxations induced by acetylcholine and A23187, and the relaxations were abolished when ciclazindol (10 microM) was combined with apamin (0.1 microM). 6. Human pial arteries from two out of four patients displayed an L-NOARG/indomethacin-resistant relaxation in response to substance P. This relaxation was abolished in both cases by pretreatment with the combination of charybdotoxin (0.1 microM) and apamin (0.1 microM), whereas each toxin had little effect alone. 7. The results suggest that Kv, but not KATP and BKCa, is involved in the EDHF-mediated relaxation in the guinea-pig basilar artery. The synergistic action of apamin and charybdotoxin (or ciclazindol) could indicate that both Kv and SKCa are activated by EDHF. However, a single type of K-channel, which may be structurally related to Kv and allosterically regulated by apamin, could also be the target for EDHF.

Modulation by the endothelium of the inhibitory effects of pinacidil and nimodipine on endothelin-induced contraction in cerebral arteries

The effects of pinacidil and nimodipine on endothelin-1-induced contractions in isolated cerebral arteries with and without endothelium were compared. The sensitivity to endothelin-1 was increased (0.5 log units) in the rabbit basilar artery after removal of the endothelium. The nitric oxide synthase inhibitor N omega-nitro-L-arginine (0.1 mM) also increased the sensitivity to endothelin-1 (0.6 log units) in basilar arteries with endothelium, whereas N omega-nitro-D-arginine (0.1 mM) and indomethacin (3 microM) had no effect, indicating that withdrawal of endothelium-derived nitric oxide may account for the enhancement of the endothelin-1-induced contraction after endothelial denudation. Pinacidil (1 microM) shifted the concentration-response curve for endothelin-1 to the right without affecting the maximal response in arteries without endothelium, but had no effect on the endothelin-1-induced contraction in vessels with endothelium. Nimodipine (1 microM) reduced the maximal endothelin-1-induced contraction by approximately 50% in both the presence and absence of endothelium, whereas the sensitivity to endothelin-1 was reduced only in vessels without endothelium. Incubation in "calcium-free" medium reduced the maximal endothelin-1-induced contraction by 69% and 80% in vessels with and without endothelium, respectively. In human pial arteries with endothelium, pinacidil did not affect the endothelin-1-induced contraction, whereas nimodipine and exposure to "calcium-free" solution reduced the maximal response by 31% and 74% respectively. The results show that, in the rabbit, pinacidil and to a lesser extent nimodipine preferentially act on cerebral arteries with disrupted endothelium, indicating that vasoactive factors liberated from the endothelium may modify the effect of a vasodilator.

Contractile effect of big endothelin-1 and its conversion to endothelin-1 in rabbit cerebral arteries

The effect of big endothelin-1 (big ET-1) and its conversion to endothelin-1 (ET-1) in rabbit cerebral arteries were examined. Big ET-1 and ET-1 induced concentration-dependent contractions in the basilar artery; ET-1 was approximately 8 times more potent than big ET-1. The metalloprotease inhibitor phosphoramidon (30 mumol/l) almost abolished the contractile response to big ET-1, whereas the ET-1-induced contraction was unaffected. Removal of the endothelium did not attenuate the big ET-1-induced contraction. ET-1 was approximately 14 times more potent than endothelin-3 (ET-3) to elicit contraction. The contractions induced by big ET-1, ET-1 and ET-3 were all inhibited by ET(A) receptor antagonist BQ 123 (3 mumol/l). The ET(B) receptor antagonist IRL 1038 (3 mumol/l) had no effect on the contractile responses to big ET-1 and ET-1, but produced a small inhibition of the ET-3-induced contraction. Formation of ET-1 was demonstrated in membrane fractions of cerebral arteries incubated with big ET-1 as measured by high pressure liquid chromatography followed by radioimmunoassay. These results suggest that externally applied big ET-1 is converted to ET-1 by a phosphoramidon-sensitive "endothelin converting enzyme" present in the vascular smooth muscle cells. The ET-1 formed subsequently mediates the big ET-1-induced contraction by activation of mainly ET(A) receptors, although a small contribution of ET(B) receptors cannot be excluded.

Substance P-induced relaxation and hyperpolarization in human cerebral arteries

1. Vascular effects of substance P were studied in human isolated pial arteries removed from 14 patients undergoing cerebral cortical resection. 2. Substance P induced a concentration-dependent relaxation in the presence of indomethacin. No relaxation was seen in arteries where the endothelium had been removed. 3. N omega-nitro-L-arginine (L-NOARG, 0.3 mM) abolished the relaxation in arteries from six patients. The relaxation was only partially inhibited in the remaining eight patients, the reduction of the maximum relaxation being less than 50% in each patient. 4. The L-NOARG-resistant relaxation was abolished when the external K+ concentration was raised above 30 mM. 5. Substance P caused a smooth muscle hyperpolarization (in the presence of L-NOARG and indomethacin), but only when the artery showed an L-NOARG-resistant relaxation. 6. The results indicate that nitric oxide is an important mediator of endothelium-dependent relaxation in human cerebral arteries. Furthermore, another endothelium-dependent pathway, causing hyperpolarization and vasodilatation, was identified in arteries from more than half the population of patients.

Enhancement of depolarization-induced contractions after endothelium denudation is not related to an impaired production of nitric oxide or prostacyclin in the rabbit basilar artery

Enhancement of the extracellular potassium ion (K+) concentration combined with endothelial injury have been suggested to occur during cerebral ischaemia-reperfusion and vasospasm after subarachnoid hemorrhage. The effect of potassium (K+) depolarization was therefore investigated in isolated segments of the rabbit basilar artery with and without an intact endothelial cell layer. Addition of potassium chloride to the organ bath induced a concentration-dependent contraction. Endothelial denudation of the artery resulted in an unstable baseline tension and a leftward shift of the K+ concentration-response curve. The K+ concentration eliciting half maximum contraction decreased from 26 mmol l-1 in the presence to 12 mmol l-1 in the absence of an intact endothelium. Nimodipine (3 x 10(-7) mol l-1) or exposure to a calcium-free medium abolished the spontaneous as well as K(+)-induced contractions. N omega-nitro-L-arginine (10(-4) mol l-1), indomethacin (3 x 10(-6) mol l-1) and glibenclamide (10(-5) mol l-1) did not affect the contractile response to K+ in intact arteries. However, N omega-nitro-L-arginine increased the baseline tension, and this effect could not be reproduced with N omega-nitro-D-arginine. Pinacidil (10(-6) mol l-1) abolished the spontaneous contractile activity in endothelium-denuded arteries and reduce the K+ sensitivity to the same level as in intact arteries. Tetraethylammonium (3 mmol l-1) and ouabain (10(-5) mol l-1) increased the basal tension and shifted the K+ concentration-response curve to the left.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of pinacidil on cerebral and mesenteric arteries--influence of the endothelium

The effect of pinacidil on the contractile response to stepwise increases of the extracellular K+ concentration ([K+]o) was investigated in isolated segments of human pial and mesenteric arteries and rabbit basilar and mesenteric arteries. The [K+]o eliciting half maximum contraction (EC50) was lower in human pial (18 mM) and rabbit basilar (27 mM) arteries than in human (33 mM) and rabbit (32 mM) mesenteric arteries, respectively. The alpha-adrenoceptor blocker, prazosin, increased the EC50 value for K+ from 27 to 40 mM and reduced the maximum response in rabbit mesenteric arteries, but had no effect on the K(+)-induced contraction in rabbit basilar arteries, indicating a substantial noradrenergic component of the K+ response in the former arteries. Removal of the endothelium decreased the EC50 value for K+ from 27 to 15 mM in rabbit basilar arteries, whereas the K+ sensitivity was unaffected in rabbit mesenteric arteries. Pinacidil shifted the K+ concentration-response curve to the right in human and rabbit cerebral and mesenteric arteries. In rabbit basilar arteries, but not in mesenteric arteries, the shift was larger in the absence than in the presence of an intact endothelium. When endothelium-denuded rabbit arteries were compared, the inhibitory effect of pinacidil was larger in basilar than in mesenteric arteries. Thus, pinacidil inhibits K(+)-induced contractions in both cerebral and mesenteric arteries, but appears to act preferentially on endothelium-denuded rabbit basilar arteries. Provided that endothelial damage and depolarization-induced vasoconstriction are of pathophysiological importance in cerebrovascular disorders such as stroke and cerebral ischemia secondary to vasospasm after subarachnoid hemorrhage, pinacidil may have a therapeutic potential.