Recurrent stroke after lobar and deep intracerebral hemorrhage: a hospital-based cohort study.

BACKGROUND: Recurrent stroke rates after intracerebral hemorrhage (ICH) vary widely between observational studies due to differences in ICH etiology and risk for thromboembolic events. We therefore aimed to assess the patient characteristics and prognosis after deep and lobar ICH in a well-characterized, multicenter, hospital-based cohort. METHODS: Patients were prospectively documented in 13 German neurological stroke centers. Of 744 patients with spontaneous ICH discharged alive, 516 (69.4%) gave informed consent and 496 (66.7%) could be followed up by central telephone interview over a mean duration of 2 years. RESULTS: In patients with deep ICH, the Kaplan-Meier estimate for stroke during the first year was 5.8% (95% CI 2.9-8.7) and the overall annual rate (calculated over a 3-year period) was 2.9% (95% CI 1.6-4.1). In patients with lobar ICH, the Kaplan-Meier estimate for stroke during the first year was 7.8% (95% CI 3.1-12.5) and the overall annual rate was 7.2% (95% CI 3.8-10.6). At the last follow-up before recurrent stroke or end of study, 141 patients (28.4%) overall received antiplatelet agents, and 12 (2.4%) received oral anticoagulation. No difference could be found for recurrent ICH under antiplatelet agents versus no antithrombotic medication. CONCLUSION: The risk of recurrent stroke after lobar ICH remains high beyond the first year, whereas it decreases after 1 year in patients with deep ICH. Antiplatelets are prescribed in a considerable number of patients even though the risk-benefit ratio after ICH remains unknown.

Algal biofuels from wastewater treatment high rate algal ponds.

This paper examines the potential of algae biofuel production in conjunction with wastewater treatment. Current technology for algal wastewater treatment uses facultative ponds, however, these ponds have low productivity (∼10 tonnes/ha.y), are not amenable to cultivating single algal species, require chemical flocculation or other expensive processes for algal harvest, and do not provide consistent nutrient removal. Shallow, paddlewheel-mixed high rate algal ponds (HRAPs) have much higher productivities (∼30 tonnes/ha.y) and promote bioflocculation settling which may provide low-cost algal harvest. Moreover, HRAP algae are carbon-limited and daytime addition of CO(2) has, under suitable climatic conditions, the potential to double production (to ∼60 tonnes/ha.y), improve bioflocculation algal harvest, and enhance wastewater nutrient removal. Algae biofuels (e.g. biogas, ethanol, biodiesel and crude bio-oil), could be produced from the algae harvested from wastewater HRAPs, The wastewater treatment function would cover the capital and operation costs of algal production, with biofuel and recovered nutrient fertilizer being by-products. Greenhouse gas abatement results from both the production of the biofuels and the savings in energy consumption compared to electromechanical treatment processes. However, to achieve these benefits, further research is required, particularly the large-scale demonstration of wastewater treatment HRAP algal production and harvest.

Nitrogen fixation in termites.

Nitrogen fixation, measured by the reduction of acetylene to ethylene, was found in workers of the dry-wood termite Kalotermes minor. The soldiers and reproductive castes fixed little or no nitrogen. The fixation rates ranged between 24 and 566 micrograms of nitrogen fixed per month per gram (wet weight) of termite. Nitrogen fixation can be a significant source of nitrogen for these termites.

Hydrogen Evolution by Nitrogen-Fixing Anabaena cylindrica Cultures.

Actively growing, nitrogen-fixing cultures of the blue-green alga Anabaena cylindrica can simultaneously evolve hydrogen and oxygen frolni water and light. Hydrogen evolution was strongly inhibited by N(2) but only slightly by CO or O(2), characteristics of the nitrogenase reaction in the heterocysts of Anabaena cylindrica. We suggest that this reaction has potential use in solar energy conversion.

Current management and risk of recurrent stroke in cerebrovascular patients with right-to-left cardiac shunt.

BACKGROUND: Right-to-left cardiac shunt (RLS) is considered a risk factor for stroke, especially in patients aged <55 years. We aimed to investigate the current management and prognosis in consecutive patients with RLS and otherwise cryptogenic cerebrovascular events. METHODS: In total, 1,126 patients with cryptogenic stroke or TIA were included from 17 German neurology departments. During a mean follow-up of 28.4 months, we assessed current antithrombotic medication, percutaneous device closure (PDC) and recurrent cerebrovascular events in 899 patients (79.8%). Stroke recurrence was compared between 548 patients without RLS and 351 patients with RLS under various prevention regimens. RESULTS: RLS was detected in 35.9% of cryptogenic cerebrovascular patients, but could not be evaluated as an independent predictor for recurrent stroke (adjusted HR 1.6, 95% CI: 0.9-2.7). In RLS-positive patients, the Kaplan-Meier estimate for stroke during the first year was 4.1% (95% CI: 1.9-6.3%) and 1.7% (95% CI: 0.9-2.4%) per year thereafter. At the last follow-up before recurrent stroke or end of study, 117 RLS-positive patients (33.3%) had received a PDC, 154 (43.9%) were receiving antiplatelets, 63 (17.9%) received anticoagulation, and 17 (4.8%) received none of the above. No association with recurrent stroke was found for the secondary preventive regime. CONCLUSION: Our multicenter hospital-based cohort study confirmed low recurrent event rates in RLS patients with otherwise cryptogenic stroke or TIA, as well as a great heterogeneity of current management. Despite the lack of scientific evidence, a substantial number of RLS-positive patients underwent PDC for secondary stroke prevention.

Adherence and quality of oral anticoagulation in cerebrovascular disease patients with atrial fibrillation.

BACKGROUND/AIMS: Low rates and poor quality of oral anticoagulation (OAC) have been reported in patients with atrial fibrillation (AF). We therefore sought to investigate the prescription patterns at discharge, adherence and quality of OAC in cerebrovascular disease patients with AF. METHODS: Consecutive ischemic stroke (IS) and transient ischemic attack (TIA) patients were prospectively documented in 11 German stroke centers. A central telephone follow-up after 1-2 years assessed the current antithrombotic medication and results of coagulation checks. RESULTS: Of 1,463 surviving patients with AF, 30.5% were discharged on OAC and 13.9% on high-dose heparin. Of 329 AF patients discharged on OAC and with consent for follow-up, 88.7% of surviving patients were still on OAC at the follow-up. Of these, 52.7% reported coagulation values out of the therapeutic range during the preceding 3 months. A recurrent IS was seen in 9 patients (2.1%/year) and an intracranial hemorrhage in 2. CONCLUSION: We found an important underuse of OAC following TIA or IS mainly in older patients and with greater stroke-related disability. Although the reported coagulation checks showed an only moderate rate within therapeutic ranges, safety and efficacy of OAC in this cohort seem comparable to previous randomized and observational trials in AF patients.

Bioremoval of heavy metals by the use of microalgae.

Bioremoval, the use of biological systems for the removal of metal ions from polluted waters, has the potential to achieve greater performance at lower cost than conventional wastewater treatment technologies for metal removal. Bioremoval capabilities of microalgae have been extensively studied, and some commercial applications have been initiated. Although microalgae are not unique in their bioremoval capabilities, they offer advantages over other biological materials in some conceptual bioremoval process schemes. Selected microalgae strains, purposefully cultivated and processed for specific bioremoval applications, have the potential to provide significant improvements in dealing with the world-wide problems of metal pollution. In addition to strain selection, significant advances in the technology appear possible by improving biomass containment or immobilization techniques and by developing bioremoval process steps utilizing metabolically active microalgae cultures. The latter approach is especially attractive in applications where extremely low levels of residual metal ions are desired. This review summarizes the current literature, highlighting the potential benefits and problems associated with the development of novel algal-based bioremoval processes for the abatement of heavy metal pollution.

Development and validation of the Essen Intracerebral Haemorrhage Score.

BACKGROUND: Spontaneous intracerebral haemorrhage (ICH) accounts for the highest in-hospital mortality of all stroke types. Nevertheless, outcome is favourable in about 30% of patients. Only one model for the prediction of favourable outcome has been validated so far. OBJECTIVE: To describe the development and validation of the Essen ICH score. METHODS: Inception cohorts were assessed on the National Institutes of Health stroke scale (NIH-SS) on admission and after follow up of 100 days. On the basis of previously validated clinical variables, a simple clinical score was developed to predict mortality and complete recovery (Barthel index after 100 days>or=95) in 340 patients with acute ICH. Subscores for age (<60=0; 60-69=1; 70-79=2; >or=80=3), NIH-SS level of consciousness (alert=0; drowsy=1; stuporose=2; comatose=3), and NIH-SS total score (0-5=0; 6-10=1; 11-15=2; 16-20=3; >20 or coma=4) were combined into a prognostic scale with <3 predicting complete recovery and >7 predicting death. The score was subsequently validated in an external cohort of 371 patients. RESULTS: The Essen ICH score showed a high prognostic accuracy for complete recovery and death in both the development and validation cohort. For prediction of complete recovery on the Barthel index after 100 days, the Essen ICH score was superior to the physicians' prognosis and to two previous prognostic scores developed for a slightly modified outcome. CONCLUSIONS: The Essen ICH score provides an easy to use scale for outcome prediction following ICH. Its high positive predictive values for adverse outcomes and easy applicability render it useful for individual prognostic indications or the design of clinical studies. In contrast, physicians tended to predict outcome too pessimistically.

Nitrogenase activity and photosynthesis in Plectonema boryanum.

Nitrogen-starved Plectonema boryanum 594 cultures flushed with N(2)/CO(2) or A/CO(2) (99.7%/0.3%, vol/vol) exhibited nitrogenase activity when assayed either by acetylene reduction or hydrogen evolution. Oxygen evolution activities and phycocyanin pigments decreased sharply before and during the development of nitrogenase activity, but recovered in the N(2)/CO(2) cultures after a period of active nitrogen fixation. Under high illumination, the onset of nitrogenase activity was delayed; however, the presence of 3-(3, 4-dichlorophenyl)-1, 1-dimethylurea (DCMU) eliminated this lag. Oxygen was a strong and irreversible inhibitor of nitrogenase activity at low (>0.5%) concentrations. In the dark, low oxygen tensions (0.5%) stimulated nitrogenase activity (up to 60% of that in the light), suggesting a limited but significant respiratory protection of nitrogenase at low oxygen tensions. DCMU was not a strong inhibitor of nitrogenase activity. A decrease in nitrogenase activity after a period of active nitrogen fixation was observed in the N(2)/CO(2-), but not in the A/CO(2-), flushed cultures. We suggest that this decrease in nitrogenase activity is due to exhaustion of stored substrate reserves as well as inhibition by the renewed oxygen evolution of the cultures. Repeated peaks of alternating nitrogenase activity and oxygen evolution were observed in some experiments. Our results indicate a temporal separation of these basically incompatible reactions in P. boryanum.

Hydrogen production by nitrogen-starved cultures of Anabaena cylindrica.

Nitrogen-starved cultures of the alga Anabaena cylindrica 629 produced hydrogen and oxygen continuously for 7 to 19 days. Hydrogen production attained a maximum level after 1 to 2 days of starvation and was followed by a slow decline. The maximum rates were 30 ml of H2 evolved per liter of culture per h or 32 mul of H2 per mg of dry weight per h. In 5 to 7 days the rate of H2 evolution by the more productive cultures fell to one-half its maximum value. The addition of 10(-4) to 5 X 10(-4) M ammonium increased the rate of oxygen evolution and the total hydrogen production of the cultures. H2-O2 ratios were 4:1 under conditions of complete nitrogen starvation and about 1.7:1 after the addition of ammonium. Thus, oxygen evolution was affected by the extent of the nitrogen starvation. Thermodynamic efficiencies of converting incident light energy to free energy of hydrogen via algal photosynthesis were 0.4%. Possible factors limiting hydrogen production were decline of reductant supply and filament breakage. Hydrogen production by filamentous, heterocystous blue-green algae could be used for development of a biophotolysis system.

Nitrogen fixation by thermophilic blue-green algae (cyanobacteria): temperature characteristics and potential use in biophotolysis.

Thermophilic, nitrogen-fixing, blue-green algae (cyanobacteria) were investigated for use in biophotolysis. Three strains of Mastigocladus laminosus were tested and were found to be equally effective in biophotolysis as judged by nitrogenase activity. The alga, M. laminosus NZ-86-m, which was chosen for further study, grew well in the temperature range from 35 to 50 degrees C, with optimum growth at 45 degrees C, at which temperature acetylene reduction activity was also greatest. The maximum tolerable temperature was 55 degrees C. Acetylene reduction activity was saturated at a light intensity of 1 x 10 ergs cm s. Atmospheric oxygen tension was found to be slightly inhibitory to acetylene reduction of both slowly growing and exponentially growing cultures. Nonsterile continuous cultures, which were conducted to test problems of culture maintenance, could be operated for 2 months without any significant decrease in nitrogenase activity or contamination by other algae. Nitrogen-starved cultures of M. laminosus NZ-86-m produced hydrogen at comparable rates to Anabaena cylindrica. The conversion efficiency of light to hydrogen energy at maximum rates of hydrogen production was 2.7%.

Hydrogen Production by the Thermophilic Alga Mastigocladus laminosus: Effects of Nitrogen, Temperature, and Inhibition of Photosynthesis.

Hydrogen production by nitrogen-limited cultures of a thermophilic blue-green alga (cyanobacterium), Mastigocladus laminosus, was studied to develop the concept of a high-temperature biophotolysis system. Biophotolytic production of hydrogen by solar radiation was also demonstrated. Hydrogen consumption activity in these cultures was relatively high and is the present limiting factor on both the net rate and duration of hydrogen production.

Photobioreactor design: Mixing, carbon utilization, and oxygen accumulation.

Photobioreactor design and operation are discussed in terms of mixing, carbon utilization, and the accumulation of photosynthetically produced oxygen. The open raceway pond is the primary type of reactor considered; however small diameter (1-5 cm) horizontal glass tubular reactors are compared to ponds in several respects. These are representative of the diversity in photobioreactor design: low capital cost, open systems and high capital cost, closed systems. Two 100-m(2) raceways were operated to provide input data and to validate analytical results. With a planktonic Chlorella sp., no significant difference in productivity was noted between one pond mixed at 30 cm/s and another mixed from 1 to 30 cm/s. Thus, power consumption or CO(2) outgassing limits maximal mixing velocities. Mixing power inputs measured in 100-m(2) ponds agreed fairly well with those calculated by the use of Manning's equation. A typically configured tubular reactor flowing full (1 cm diameter, 30 cm/s) consumes 10 times as much energy as a typical pond (20 cm deep flowing at 20 cm/s). Tubular reactors that flow only partially full would be limited by large hydraulic head losses to very short sections (as little as 2 m length at 30 cm/s flow) or very low flow velocities. Open ponds have greater CO(2) storage capacity than tubular reactors because of their greater culture volume per square meter (100-300 L/m(2) vs. 8-40 L/m(2) for 1-5-cm tubes). However, after recarbonation, open ponds tend to desorb CO(2) to the atmosphere. Thus ponds must be operated at higher pH and lower alkalinity than would be possible with tubular reactors if cost of carbon is a constraint. The mass transfer coefficient, K(L), for CO(2) release through the surface of a 100-m(2) pond was determined to be 0.10 m/h. Oxygen buildup would be a serious problem with any enclosed reactor, especially small-diameter tubes. At maximal rates of photosynthesis, a 1-cm tubular reactor would accumulate 8-10 mg O(2)/L/min. This may result in concentrations of oxygen reaching 100 mg/L, even with very frequent gas exchange. In an open pond, dissolved oxygen rises much more slowly as a consequence of the much greater volume per unit surface area and the outgassing of oxygen to the atmosphere. The maximum concentration of dissolved oxygen is typically 25-40 mg/L. The major advantage of enclosed reactors lies in the potential for aseptic operation, a product value which justifies the expense. For most products of algal mass cultivation, open ponds are the only feasible photobioreactor design capable of meeting the economic and operating requirements of such systems, provided desirable species can be maintained.

Physiological Studies of Oxygen Protection Mechanisms in the Heterocysts of Anabaena cylindrica.

The mechanism of O(2) protection of nitrogenase in the heterocysts of Anabaena cylindrica was studied in vivo. Resistance to O(2) inhibition of nitrogenase activity correlated with the O(2) tension of the medium in which heterocyst formation was induced. O(2) resistance also correlated with the apparent K(m) for acetylene, indicating that O(2) tension may influence the development of a gas diffusion barrier in the heterocysts. The role of respiratory activity in protecting nitrogenase from O(2) that diffuses into the heterocyst was studied using inhibitors of carbon metabolism. Reductant limitation induced by 3-(3,4-dichlorophenyl)-1, 1-dimethylurea increased the O(2) sensitivity of in vivo acetylene reduction. Azide, at concentrations (30 mM) sufficient to completely inhibit dark nitrogenase activity (a process dependent on oxidative phosphorylation for its ATP supply), severely inhibited short-term light-dependent acetylene reduction in the presence of O(2) but not in its absence. After 3 h of aerobic incubation in the presence of 20 mM azide, 75% of cross-reactive component I (Fe-Mo protein) in nitrogenase was lost; less than 35% was lost under microaerophilic conditions. Sodium malonate and monofluoroacetate, inhibitors of Krebs cycle activity, had only small inhibitory effects on nitrogenase activity in the light and on cross-reactive material. The results suggest that oxygen protection is dependent on both an O(2) diffusion barrier and active respiration by the heterocyst.