Search

Rapid warming in the Arctic is drastically impacting marine ecosystems, affecting species communities and food-web structure. Pelagic Themisto amphipods are a major component of the Arctic zooplankton community and represent a key link between secondary producers and marine vertebrates at higher trophic levels. Two co-existing species dominate in the region: the larger Themisto libellula , considered a true polar species and the smaller Themisto abyssorum , a sub-Arctic, boreal-Atlantic species. Recent changes in abundance and distribution ranges have been detected in both species, likely due to the Atlantification of the Arctic. The ecology and genetic structure of these species are understudied, despite their high biomass and importance in the food web. For both species, we assessed genetic diversity, patterns of spatial genetic structure and demographic history using samples from the Greenland shelf, Fram Strait and Svalbard. This was achieved by analysing variation on the mitochondrial cytochrome c oxidase subunit 1 gene (mtCOI). The results revealed contrasting levels of mtCOI diversity: low levels in T. libellula and high levels in T. abyssorum . A lack of spatial genetic structure and a high degree of genetic connectivity were detected in both species in the study region. These patterns of diversity are potentially linked to the impacts of the Last Glacial Maximum. T. libellula populations may have been isolated in glacial refugia, undergoing gene flow restriction and vicariant effects, followed by a population expansion after deglaciation. Whereas T. abyssorum likely maintained a stable, widely distributed metapopulation further south, explaining the high diversity and connectivity. This study provides new data on the phylogeography of two ecologically important species, which can contribute to predicting how zooplankton communities and food-web structure will manifest in the rapidly changing Arctic., Competing Interests: None declared., (© 2023 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.)

Species identification is pivotal in biodiversity assessments and proteomic fingerprinting by MALDI-TOF mass spectrometry has already been shown to reliably identify calanoid copepods to species level. However, MALDI-TOF data may contain more information beyond mere species identification. In this study, we investigated different ontogenetic stages (copepodids C1-C6 females) of three co-occurring Calanus species from the Arctic Fram Strait, which cannot be identified to species level based on morphological characters alone. Differentiation of the three species based on mass spectrometry data was without any error. In addition, a clear stage-specific signal was detected in all species, supported by clustering approaches as well as machine learning using Random Forest. More complex mass spectra in later ontogenetic stages as well as relative intensities of certain mass peaks were found as the main drivers of stage distinction in these species. Through a dilution series, we were able to show that this did not result from the higher amount of biomass that was used in tissue processing of the larger stages. Finally, the data were tested in a simulation for application in a real biodiversity assessment by using Random Forest for stage classification of specimens absent from the training data. This resulted in a successful stage-identification rate of almost 90%, making proteomic fingerprinting a promising tool to investigate polewards shifts of Atlantic Calanus species and, in general, to assess stage compositions in biodiversity assessments of Calanoida, which can be notoriously difficult using conventional identification methods., (© 2022 The Authors. Molecular Ecology Resources published by John Wiley & Sons Ltd.)

The two congeneric hyperiids Themisto libellula and T. abyssorum provide an important trophic link between lower and higher trophic levels in the rapidly changing Arctic marine ecosystem. These amphipods are characterized by distinct hydrographic affinities and are hence anticipated to be impacted differently by environmental changes, with major consequences for the Arctic food web. In this study, we applied DNA metabarcoding to the stomach contents of these Themisto species, to comprehensively reveal their prey spectra at an unprecedented-high-taxonomic-resolution and assess the regional variation in their diet across the Fram Strait. Both species feed on a wide variety of prey but their diet strongly differed in the investigated summer season, showing overlap for only a few prey taxa, such as calanoid copepods. The spatially structured prey field of T. libellula clearly differentiated it from T. abyssorum, of which the diet was mainly dominated by chaetognaths. Our approach also allowed the detection of previously overlooked prey in the diet of T. libellula , such as fish species and gelatinous zooplankton. We discuss the reasons for the differences in prey spectra and which consequences these may have in the light of ongoing environmental changes.

The meroplanktonic larvae of benthic organisms are an important seasonal component of the zooplankton in temperate coastal waters. The larvae of the reef-building polychaete Lanice conchilega contribute up to 15% of the summer zooplankton biomass in the North Sea. Despite their importance for reef maintenance (which positively affects the benthic community), little is known about the trophic ecology of this meroplanktonic larva. Qualitative and quantitative estimates of carbon (C) transfer between trophic levels and of fatty acid (FA)-specific assimilation, biosynthesis, and bioconversion can be obtained by compound-specific stable isotope analysis of FA. The present work tested the hypothesis that the concept of fatty acid trophic markers (FATM), widely used for studies on holoplankton with intermediate to high lipid contents, is also applicable to lipid-poor organisms such as meroplanktonic larvae. The incorporation of isotopically-enriched dietary C by L. conchilega larvae was traced, and lipid assimilation did not follow FA-specific relative availabilities in the diet. Furthermore, FAs that were unavailable in the diet, such as 22:5(n-3), were recorded in L. conchilega, suggesting their bioconversion by the larvae. The results indicate that L. conchilega larvae preferentially assimilate certain FAs and regulate their FA composition (lipid homeostasis) independently of that of their diet. Their quasi-homeostatic response to dietary FA availability could imply that the concept of FATM has limited application in lipid-poor organisms such as L. conchilega larvae., Competing Interests: The authors have declared that no competing interests exist.

Hyperiid amphipods are predatory pelagic crustaceans that are particularly prevalent in high-latitude oceans. Many species are likely to have co-evolved with soft-bodied zooplankton groups such as salps and medusae, using them as substrate, for food, shelter or reproduction. Compared to other pelagic groups, such as fish, euphausiids and soft-bodied zooplankton, hyperiid amphipods are poorly studied especially in terms of their distribution and ecology. Hyperiids of the genus Themisto, comprising seven distinct species, are key players in temperate and cold-water pelagic ecosystems where they reach enormous levels of biomass. In these areas, they are important components of marine food webs, and they are major prey for many commercially important fish and squid stocks. In northern parts of the Southern Ocean, Themisto are so prevalent that they are considered to take on the role that Antarctic krill play further south. Nevertheless, although they are around the same size as krill, and may also occur in swarms, their feeding behaviour and mode of reproduction are completely different, hence their respective impacts on ecosystem structure differ. Themisto are major predators of meso- and macrozooplankton in several major oceanic regions covering shelves to open ocean from the polar regions to the subtropics. Based on a combination of published and unpublished occurrence data, we plot out the distributions of the seven species of Themisto. Further, we consider the different predators that rely on Themisto for a large fraction of their diet, demonstrating their major importance for higher trophic levels such as fish, seabirds and mammals. For instance, T. gaudichaudii in the Southern Ocean comprises a major part of the diets of around 80 different species of squid, fish, seabirds and marine mammals, while T. libellula in the Bering Sea and Greenland waters is a main prey item for commercially exploited fish species. We also consider the ongoing and predicted range expansions of Themisto species in light of environmental changes. In northern high latitudes, sub-Arctic Themisto species are replacing truly Arctic, ice-bound, species. In the Southern Ocean, a range expansion of T. gaudichaudii is expected as water masses warm, impacting higher trophic levels and biogeochemical cycles. We identify the many knowlegde gaps that must be filled in order to evaluate, monitor and predict the ecological shifts that will result from the changing patterns of distribution and abundance of this important pelagic group., (© 2019 Elsevier Ltd. All rights reserved.)

Long-term data sets are essential to understand climate-induced variability in marine ecosystems. This study provides the first comprehensive analysis of longer-term temporal and spatial variations in zooplankton abundance and copepod community structure in the northern Benguela upwelling system from 2005 to 2011. Samples were collected from the upper 200 m along a transect at 20 °S perpendicular to the coast of Namibia to 70 nm offshore. Based on seasonal and interannual trends in surface temperature and salinity, three distinct time periods were discernible with stronger upwelling in spring and extensive warm-water intrusions in late summer, thus, high temperature amplitudes, in the years 2005/06 and 2010/11, and less intensive upwelling followed by weaker warm-water intrusions from 2008/09 to 2009/10. Zooplankton abundance reflected these changes with higher numbers in 2005/06 and 2010/11. In contrast, zooplankton density was lower in 2008/09 and 2009/10, when temperature gradients from spring to late summer were less pronounced. Spatially, copepod abundance tended to be highest between 30 and 60 nautical miles off the coast, coinciding with the shelf break and continental slope. The dominant larger calanoid copepods were Calanoides carinatus, Metridia lucens and Nannocalanus minor. On all three scales studied, i.e. spatially from the coast to offshore waters as well as temporally, both seasonally and interannually, maximum zooplankton abundance was not coupled to the coldest temperature regime, and hence strongest upwelling intensity. Pronounced temperature amplitudes, and therefore strong gradients within a year, were apparently important and resulted in higher zooplankton abundance.

Oxygen minimum zones (OMZs) affect distribution patterns, community structure and metabolic processes of marine organisms. Due to the prominent role of zooplankton, especially copepods, in the marine carbon cycle and the predicted intensification and expansion of OMZs, it is essential to understand the effects of hypoxia on zooplankton distribution and ecophysiology. For this study, calanoid copepods were sampled from different depths (0-1800 m) at eight stations in the eastern tropical Atlantic (3 °47'N to 18 °S) during three expeditions in 2010 and 2011. Their horizontal and vertical distribution was determined and related to the extent and intensity of the OMZ, which increased from north to south with minimum O2 concentrations (12.7 µmol kg(-1)) in the southern Angola Gyre. Calanoid copepod abundance was highest in the northeastern Angola Basin and decreased towards equatorial regions as well as with increasing depth. Maximum copepod biodiversity was observed in the deep waters of the central Angola Basin. Respiration rates and enzyme activities were measured to reveal species-specific physiological adaptations. Enzyme activities of the electron transport system (ETS) and lactate dehydrogenase (LDH) served as proxies for aerobic and anaerobic metabolic activity, respectively. Mass-specific respiration rates and ETS activities decreased with depth of occurrence, consistent with vertical changes in copepod body mass and ambient temperature. Copepods of the families Eucalanidae and Metridinidae dominated within the OMZ. Several of these species showed adaptive characteristics such as lower metabolic rates, additional anaerobic activity and diel vertical migration that enable them to successfully inhabit hypoxic zones.

Life-cycles of polar herbivorous copepods are characterised by seasonal/ontogenetic vertical migrations and diapause to survive periods of food shortage during the long winter season. However, the triggers of vertical migration and diapause are still far from being understood. In this study, we test the hypothesis that acidic pH and the accumulation of ammonium (NH4 (+)) in the hemolymph contribute to the control of diapause in certain Antarctic copepod species. In a recent study, it was already hypothesized that the replacement of heavy ions by ammonium is necessary for diapausing copepods to achieve neutral buoyancy at overwintering depth. The current article extends the hypothesis of ammonium-aided buoyancy by highlighting recent findings of low pH values in the hemolymph of diapausing copepods with elevated ammonium concentrations. Since ammonia (NH3) is toxic to most organisms, a low hemolymph pH is required to maintain ammonium in the less toxic ionized form (NH4 (+)). Recognizing that low pH values are a relevant factor reducing metabolic rate in other marine invertebrates, the low pH values found in overwintering copepods might not only be a precondition for ammonium accumulation, but in addition, it may insure metabolic depression throughout diapause.

Following up on previous investigations on the stress resistance of corals, this study assessed the trophic plasticity of the coral Stylophora subseriata in the Spermonde Archipelago (Indonesia) along an eutrophication gradient. Trophic plasticity was assessed in terms of lipid content and fatty acid composition in the holobiont relative to its plankton (50-300 μm) food as well as the zooxanthellae density, lipid, FA and chlorophyll a content. A cross-transplantation experiment was carried out for 1.5 months in order to assess the trophic potential of corals. Corals, which live in the eutrophied nearshore area showed higher zooxanthellae and chlorophyll a values and higher amounts of the dinoflagellate biomarker FA 18:4n-3. Their lipid contents were maintained at similar to levels from specimens further away from the anthropogenic impact source going up to 14.9 ± 0.9 %. A similarity percentage analysis of the groups holobiont, zooxanthellae and plankton >55 μm found that differences between the FA composition of the holobiont and zooxanthellae symbionts were more distinct in the site closer to the shore, thus heterotrophic feeding became more important. Transplanted corals attained very similar zooxanthellae, chlorophyll a and lipid values at all sites as the specimens originating from those sites, which indicates a high potential for trophic plasticity in the case of a change in food sources, which makes this species competitive and resistant to eutrophication.

Deep-sea biodiversity has received increasing interest in the last decade, mainly focusing on benthic communities. In contrast, studies of zooplankton in the meso- to bathypelagic zones are relatively scarce. In order to explore evolutionary processes in the pelagic deep sea, the present study focuses on copepods of two clausocalanoid families, Euchaetidae and Aetideidae, which are abundant and species-rich in the deep-sea pelagic realm. Molecular phylogenies based on concatenated-portioned data on 18S, 28S and internal transcribed spacer 2 (ITS2), as well as mitochondrial cytochrome c oxidase subunit I (COI), were examined on 13 species, mainly from Arctic and Antarctic regions, together with species-specific biological traits (i.e. vertical occurrence, feeding behaviour, dietary preferences, energy storage, and reproductive strategy). Relationships were resolved on genus, species and even sub-species levels, the latter two established by COI with maximum average genetic distances ranging from ≤5.3% at the intra-specific, and 20.6% at the inter-specific level. There is no resolution at a family level, emphasising the state of Euchaetidae and Aetideidae as sister families and suggesting a fast radiation of these lineages, a hypothesis which is further supported by biological parameters. Euchaetidae were similar in lipid-specific energy storage, reproductive strategy, as well as feeding behaviour and dietary preference. In contrast, Aetideidae were more diverse, comprising a variety of characteristics ranging from similar adaptations within Paraeuchaeta, to genera consisting of species with completely different reproductive and feeding ecologies. Reproductive strategies were generally similar within each aetideid genus, but differed between genera. Closely related species (congeners), which were similar in the aforementioned biological and ecological traits, generally occurred in different depth layers, suggesting that vertical partitioning of the water column represents an important mechanism in the speciation processes for these deep-sea copepods. High COI divergence between Arctic and Antarctic specimens of the mesopelagic cosmopolitan Gaetanus tenuispinus and the bipolar Aetideopsis minor suggest different geographic forms, potentially cryptic species or sibling species. On the contrary, Arctic and Antarctic individuals of the bathypelagic cosmopolitans Gaetanus brevispinus and Paraeuchaeta barbata were very similar in COI sequence, suggesting more gene flow at depth and/or that driving forces for speciation were less pronounced in bathypelagic than at mesopelagic depths., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Oceanic zooplankton species exhibit quite diverse life history traits. A major driving force determining their life strategies is the seasonal variability in food supply, which is most pronounced in polar oceans where fluctuations in primary production are extreme. Seasonal adaptations are closely related to the trophic level of zooplankters, with strongest pressures occurring on herbivorous organisms. The dominant grazers, calanoid copepods and krill (Euphausiacea), have developed fascinating solutions for successful overwintering at higher latitudes. They usually exhibit a very efficient storage and utilization of energy reserves to reduce the effect of a highly seasonal primary production. The predominant larger Calanus species from the Arctic and Calanoides acutus from the Antarctic biosynthesize large amounts of high-energy wax esters with long-chain monounsaturated fatty acids and alcohols (20:1 and 22:1 isomers) as major components. They survive the dark season at depth in a stage of dormancy called diapause. In contrast, the Antarctic Calanus propinquus, a winter-active species, synthesizes primarily triacylglycerols, which are dominated by long-chain monounsaturated fatty acids with 22 carbon atoms (2 isomers) and yield even higher calorific contents. The omnivorous and carnivorous species, which are less subjected to seasonal food shortage, usually do not exhibit such an elaborate lipid biosynthesis. Herbivores usually do not utilize much of their enormous lipid reserves for overwintering, but channel this energy towards reproductive processes in late winter/early spring. Timing of reproduction is critical especially at high latitudes due to the short production period, and lipid reserves ensure early spawning independent of external resources. These energetic adaptations (dormancy, lipid storage) are supplemented by other life strategies such as extensive vertical migrations, change in the mode of life, and trophic flexibility.

Two-day treatment with activator (equimolar streptokinase-human plasminogen complex) was given to 26 patients. Indications were chronic arterial occlusion and stenosis of the lower-limb arteries (25 patients), and thrombosis of the subclavian veins. The onset of claudication had on average been 7.5 months previously, average walking distance 288 metres. Five occlusions of iliac arteries and three of femoral arteries were removed. In addition, stenosis of the aorta (one case), the iliac artery (ten cases) and femoral artery (one case) was partly removed. Occlusion of the axillary vein was also removed. Average duration of the successfully treated occlusions was 4.3 months. Those stenoses that responded to activator had the well-known morphological criteria for fibrinolysis. The walking distance of the patients increased from an average of 288 to 401 metres. Activator treatment was well tolerated. No serious, especially cerebral, complications occurred. The most striking laboratory finding was of circulating plasmin during the entire duration of the infusion.

In a multicentre study 15 physicians investigated the therapeutic efficacy and tolerance of Faktu suppositories and ointment (containing the active principle of Albothyl, a condensation product of m-cresolsulfonic acid and formaldehyde) in 585 patients with proctological affections. Highly satisfactory results were achieved in 486 patients (83.1%). The following were found to be the main indications: -treatment of wounds after proctological operations, -fresh and fissures, -bleeding internal haemorrhoids, -anal eczema and anal pruritus, -rhagades and perforated or prolapsed external haemorrhoids (perianal thrombosis). None of the investigators reported any persisting adverse side-effects. 16% of the patients complained of local discomfort of varying intensity such as pruritus, burning or irritation. The symptoms mostly appeared on commencement of the treatment and necessitated discontinuation of therapy in 5.3% only. The extremely favourable effect of Albothyl - the active principle of Faktu - is due to its unique mechanism of action: the markedly acid milieu of the substance. Furthermore the Faktu preparations do not contain any steroids and consequently they can be used without any misgivings over prolonged periods.

144 patients were treated with 50.000 or 100.000 fibrinolytic units (U) activator per hour over a period of up to 5 days. The drug is not yet available but in trial for the time being. We report on a survey of laboratory results in 32 of these patients. The plasminogen content of 100.000 U activator is comparable to the plasminogen content of 29 ml plasma. During activator infusion laboratory findings showed a moderate fall in plasminogen and fibrinogen. Plasmin activity was measurable during the whole period of treatment while antiplasmin was lowered considerably. There was a distinct hypocoagulabilty during activator infusion visible by a prolongation of the thrombin time and aPTT. Interestingly, no measurable activator or streptokinase activities appeared in the plasma during activator infusion. This is in contrast to findings with conventional streptokinase infusion schemes.

Streptokinase was dissolved in various solvents and the decay recorded. The method employed was a recently described clot lysis assay for quantitative streptokinase determination. The decrease in activity of 5 u streptokinase, 1500 u streptokinase, and 50,000 u steptokinase dissolved in one milliltre of different solvents (NaCl solution, glucose solution, laevulose solution, dextran solution (Rheomacrodex), gelatin solution (Haemaccel, starch solution (Plasmasteril,albumin solution, Michaelis buffer, heparin-glucose solution) and incubated over various periods of time (15 min, 30 min, 45 min, 60 min, 4h, 8h, 12h, 48h) was investigated. Solution media tested for streptokinase-potecting quality were broken down into three groups.-Group I: Solvents displaying excellent stabilizing properties (gelatin, albumin).-Group II: Solvents displaying medium stabilizing properties (dextran, levulose)--Group III: Solvents displaying properties (starch, NaCl, glucose, Michaelis buffer).--In testing streptokinase concentrations as used for therapeutic purpose (1500 u/ml, 50,000 u/ml), no decay was found to take place over observation periods as long as 48 h. This finding was independent of the different solvents (Group I, II or III) employed. Heparin stored with streptokinase at rooom temperature did not alter the streptokinase stability. From the clinical point of view, the choice of solvents for streptokinase infusion turned out to be of minor importance.

In connection with fibrinolytic therapy, it is of interest to know how much plasminogen is contained in different commercially available figrinogen preparations. This problem was investigated with the aid of a semiquantitative determination of plasminogen. The determined plasminogen content was compared with plasminogen concentration of pooled human plasma. Using the ratio of plasminogen to fibrinogen, and fixing the plasminogen content of human plasma arbitrarily at 100%, the proportion of plasminogen in fibrinogen from Immuno is 134%, fibrinogen from Behringwerke contains 13.7%, and Kabi-fibrinogen contains 2.71% plasminogen.

A method of a quantitative determination of plasma streptokinase concentrations in patients undergoing streptokinase infusion is described. The principle of this method is based on the clot lysis time recorded by the thromboelastograph. The test clot constituents were bovine fibrin, bovine plasminogen, human euglobulin, EDTA, human plasma (of unknown streptokinase quantity) and thrombin. As rather high concentrations (fixed excess) of plasminogen (euglobulin) and fibrinogen were present in the test coagulum, no interference with changing plasminogen and fibrinogen levels of the patient's plasma was observed. Furthermore, due to high EDTA concentrations, no interaction with platelet functions and coagulation factors took place. The standard deviation in measuring 2 u streptokinase in 1 ml human plasma was determined as s = +/- 0.19 u/ml, of 5 u streptokinase at s = +/- 0.47 u/ml and of 20 u streptokinase at s = +/- 2.5 u in 1 ml of human plasma. Plasma samples of patients undergoing fibrinolytic treatment were investigated with regard to their streptokinase content. Streptokinase concentration values varied between 0.7 u and 15 u/ml plasma. The average half life of streptokinase in the organism was 18 min. The decay of streptokinase in plasma at different temperatures and over various periods of time was also determined. A considerable loss of streptokinase in the plasma during storage at room temperature could be observed. Therefore, the determination procedures should be carried out without delay.

Fifty-three untreated borderline hypertensives and 73 normotensives were randomly selected from 1342 adolescents (age range 23-27 years) who were examined in 1975, 1976 and 1980 in an epidemiological study. Blood pressure was 127.2 +/- 1.0/79.0 +/- 0.8 mmHg in normotensives and 147.2 +/- 1.6/93.7 +/- 1.1 mmHg in hypertensives (P < 0.001). Erythrocyte deformability was measured with a positive pressure filter system (pore diameter 5 microns) at 37 degrees C. Erythrocyte deformability was significantly increased in hypertensives with a value of 1.77 +/- 0.05, compared with 1.64 +/- 0.04 in normotensives (P < 0.05). No difference in apparent whole blood viscosity, haematocrit and plasma fibrinogen was measurable between the groups. Although plasma noradrenaline and adrenaline concentration at rest and after 3 min standing were not different, excretion of urinary catecholamines was significantly elevated in hypertensives with 155.0 +/- 3.3 micrograms/24 h (normotensives: 100.7 +/- 5.3 micrograms/24 h; P < 0.001).

Twelve patients (age 33-77 years, mean age 68.4 years) with peripheral vascular disease (PVD) stage III-IV received continuous intravenous infusions of 5 ng prostacyclin (PGI2)/kg/min and physiological saline for 7 days. The administration was randomized and double-blind with an interval of 7 days between the infusions. During PGI2 infusion systolic blood pressure fell significantly from 147.8 +/- 4.8 mm Hg to 140.6 +/- 4.0 mm Hg (P less than 0.01) and returned to 144.5 +/- 4.9 mm Hg post infusion. Transcutaneous pO2 (tcpO2) measured on the instep of the affected limb increased significantly by 8.9 +/- 3.8 Torr during PGI2 infusion and remained elevated during the subsequent week. A significant reduction of pain was observed from the 5th day of PGI2 infusion, lasting for at least the following observation period. Platelet cAMP increased from 18.8 +/- 1.5 pmol/10(8) platelets to 24.7 +/- 1.6 pmol/10(8) platelets on the 3rd day of PGI2 infusion (P less than 0.01). Spontaneous platelet aggregation was also significantly reduced during PGI2 infusion. However, 7 days after the infusion thromboxane B2 (TXB2) in plasma and spontaneous platelet aggregation significantly increased in comparison with the preinfusion values, indicating a rebound phenomenon. The clinical outcome was favorable in 9 of 12 patients, was unchanged in two patients, while progressing to limb amputation in one patient.

Ten patients with 13 stenoses in the pelvic area were treated with low doses of streptokinase (30 000 U/h) for 72 hours. A significant improvement in the degree of stenosis was obtained as shown by post-stenotic pressure values. Biochemically there was a marked plasminaemia with moderately low fibrinogen levels. Streptokinase treatment with low doses could form an alternative method of treatment in arterial stenoses.

21 patients (aged 28-81 years) with recent subarachnoid hemorrhage (10 saccular aneurysms, 3 arteriovenous angiomas, 8 normal angiograms) were continuously infused with tranexamic acid at a dosage of 5 g daily for up to 14 days. Therapy was surveyed by daily measurement of the available plasminogen activity (aPl) with the chromogenic substrate S-2251 and by a modified bioassay, whereby the concentration of tranexamic acid was determined thrombelastographically and expressed as antifibrinolytic equivalent. In addition, a battery of blood coagulation tests was performed daily. 5 patients died, 1 after postoperative stroke, 3 as a result of general complications during intensive care treatment, but only 1 due to rebleeding. 4 patients were successfully operated during the first week, 1 patient after 2 weeks. aPl fell from 99.2% (SEM 3.0%, n = 21) before treatment to 72.9% (SEM 3.5%, n = 21) after 24 h and to the therapeutic level between 50 and 60% from day 2 on. The mean steady state of the antifibrinolytic equivalent corresponded to about 150 micrograms/ml of tranexamic acid during infusion. Intra- and interindividual changes were relatively small for aPl, when compared with the antifibrinolytic equivalent measured by the bioassay. In 2 elderly patients tranexamic acid infusion had to be terminated because of clinical and laboratory signs of disseminated intravascular coagulation, whereby aPl fell below the therapeutic range, elucidating that this method is a sensitive indicator for a hypercoagulable state and useful for the surveillance of therapy with antifibrinoltic agents.