bluuebunny/crossref_metadata_2025_split huggingface dataset:
Immune activation and degradation of tryptophan in coronary heart disease
Authors: Wirleitner B. , Rudzite V. , Neurauter G. , Murr C. , Kalnins U. , Erglis A. , Trusinskis K. , Fuchs D. 
Published: June 2003

AbstractBackground Inflammation and immune activation appear to be important in the pathogenesis of coronary heart disease (CHD). Cytokine interferon‐γ, which is released during cell‐mediated immune responses, induces indoleamine (2,3)‐dioxygenase (IDO), an enzyme degrading tryptophan to kynurenine. Therefore, immune stimulation is commonly associated with an increased kynurenine to tryptophan ratio (kyn trp−1) indicative for activated indoleamine (2,3)‐dioxygenase and a measurable decline of tryptophan.Methods Blood concentrations of kynurenine and free tryptophan and the kynurenine to tryptophan ratio were examined in 35 patients with coronary heart disease verified by coronary angiography and compared with healthy controls. Patients were observed before percutaneus transluminal coronary angioplasty (21 patients: one with artery disease, nine with 2‐ or 3‐artery disease, and five with restenosis).Results and conclusions Decreased tryptophan concentrations were found in a significant proportion of coronary heart disease patients and coincided with increased kyn trp−1 and also with increased neopterin concentrations, indicating an activated cellular immune response. We conclude that in coronary heart disease immune activation is associated with an increased rate of tryptophan degradation and thereby lowered tryptophan levels. Results may provide a basis for a better understanding of the pathogenesis of mood disturbances and depression in coronary heart disease patients.
Impaired vasodilator responses to atrial natriuretic peptide in essential hypertension
Authors: Bulut D. , Potthast R. , Hanefeld C. , Schulz T. , Kuhn M. , Mügge A. 
Published: June 2003

AbstractBackground Atrial natriuretic peptide (ANP) has vasodilating and diuretic/natriuretic properties, both of which contribute to lower blood pressure. These effects are mediated by binding of ANP to a cell‐surface receptor [type A guanylyl cyclase (GC‐A)]. It has been demonstrated by studies in monogenetic mouse models that the ANP/GC‐A system participates in the maintenance of blood pressure homeostasis.Methods In male patients with essential hypertension (EH; n = 36) as the only cardiovascular risk factor and normotensive controls (n = 12), blood flow was measured in the forearm circulation in response to i.a. infusion of synthetic human ANP, acetylcholine, orciprenaline, and sodium nitroprusside by strain‐gauge venous plethysmography. In blood samples, cyclic guanosine′5‐monophosphate (cGMP) and ANP concentrations were measured at resting conditions and during exogenous ANP infusion. In 200 patients with EH, genomic DNA was screened for an inhibitory deletion mutation of the GC‐A gene, which has been recently linked to EH in a Japanese cohort.Results The vasodilatations in response to ANP and acetylcholine were impaired in the forearm circulation of patients with EH, whereas the responses to orciprenaline and nitroprusside were preserved. Plasma ANP and cGMP concentrations were increased in the patients with EH both at resting conditions and during ANP infusion; the resting plasma cGMP levels correlated significantly with the plasma ANP levels (r = 0·68). A specific deletion mutation of the GC‐A gene did not account for the diminished relaxant effects of ANP in our study population.Conclusions The vascular ANP/GC‐A pathway is altered in patients with EH, in addition to the known defects on the nitric oxide/cGMP pathway. Attenuation of the vasodilative responses to ANP suggests impaired receptor or postreceptor responsiveness of GC‐A. It is possible that this dysfunction participates in the pathomechanism of EH.
Expression of matrix metalloproteinase‐9 in mononuclear cells of hyperhomocysteinaemic subjects
Authors: Holven K. B. , Halvorsen B. , Schulz H. , Aukrust P. , Ose L. , Nenseter M. S. 
Published: June 2003

AbstractAtherosclerotic plaque instability and rupture requires extracellular matrix modification, a complex process regulated by matrix metalloproteinases (MMPs). We hypothesized that homocysteine's atherogenic effects may involve MMP‐mediated mechanisms. Our results showed the following: (i) Compared with healthy control subjects (n = 9), patients with hyperhomocysteinaemia (n = 9) had elevated mRNA levels of MMP‐9 and tissue inhibitors of metalloproteinases‐1 (TIMP‐1) in freshly isolated peripheral blood mononuclear cells (PBMCs), which were positively correlated with homocysteine and negatively correlated with folate and vitamin B12 levels. (ii) Peripheral blood mononuclear cells obtained from these patients released markedly enhanced the amount of MMP‐9 upon oxidized LDL (oxLDL) stimulation, whereas no such enhancing effect was seen in cells from healthy controls. (iii) During folic acid 6 weeks’ treatment, normalization of homocysteine levels was accompanied by a significant reduction in mRNA levels of MMP‐9 and TIMP‐1 in PBMCs, as well as a marked reduction in oxLDL‐stimulated release of MMP enzyme activity. These novel findings may suggest that homocysteine exerts its atherogenic effect in part by elevating levels and activity of MMPs, which in turn may enhance matrix degradation, potentially promoting atherogenesis and plaque instability. Moreover, our findings suggest that folic acid supplementation may down‐regulate these inappropriate responses in these patients.
Alternative sources of beta cells for cell therapy of diabetes
Authors: Scharfmann R. 
Published: June 2003

AbstractType 1 and type 2 diabetes affect 150 million people worldwide. This is a result of the incapacity of pancreatic beta cells to produce and secrete enough insulin. Transplantation of pancreatic beta cells represents a potential therapeutic approach for type 1 diabetes. However, one limitation is the insufficient amount of beta cells available for grafts. Alternative sources of beta cells have yet to be defined. During the past years, progress has been made in the definition of new strategies to produce mature pancreatic beta cells. Different cell sources are currently tested for their capacity to differentiate into mature beta cells. In this review, I will summarize the status of our knowledge in the field of cell therapy for diabetes.
Coupled biogeochemical and hydrological responses of streams and rivers to drought
Authors: Dahm Clifford N. , Baker Michelle A. , Moore Douglas I. , Thibault James R. 
Published: June 2003

Summary

Severe or extreme droughts occurred about 10% of the time over a 105‐year record from central New Mexico, U.S.A., based on the Palmer Drought Severity Index.
Drought lowers water tables, creating extensive areas of groundwater recharge and fragmenting reaches of streams and rivers. Deeper groundwater inputs predominate as sources of surface flows during drought. Nutrient inputs to streams and rivers reflect the biogeochemistry of regional ground waters with longer subsurface residence times.
Inputs of bioavailable dissolved organic carbon to surface waters decrease during drought, with labile carbon limitation of microbial metabolism a byproduct of drought conditions.
Decreased inputs of organic forms of carbon, nitrogen and phosphorus and a decrease in the organic : inorganic ratio of nutrient inputs favours autotrophs over heterotrophs during drought.
The fate of autotrophic production during drought will be strongly influenced by the structure of the aquatic food web within impacted sites.
Parallels and contrasts in the effects of drought on stream macroinvertebrate assemblages
Authors: Boulton Andrew J. 
Published: June 2003

Summary

It is axiomatic that unusually long dry periods (droughts) adversely affect aquatic biota. Recovery after drought is rapid by macroinvertebrates that possess strategies to survive drying or are highly mobile but other taxa take longer to recolonise depending on the timing, intensity, and duration of the dry phase.
Although drought acts as a sustained ‘ramp’ disturbance, impacts may be disproportionately severe when certain critical thresholds are exceeded. For example, ecological changes may be gradual while a riffle dries but cessation of flow causes abrupt loss of a specific habitat, alteration of physicochemical conditions in pools downstream, and fragmentation of the river ecosystem. Many ecological responses to drought within these habitats apparently depend on the timing and rapidity of hydrological transitions across these thresholds, exhibiting a ‘stepped’ response alternating between gradual change while a threshold is approached followed by a swift transition when a habitat disappears or is fragmented.
In two Australian intermittent streams, drought conditions eliminated or decimated several groups of macroinvertebrates, including atyid shrimps, stoneflies and free‐living caddisflies. These taxa persisted during the early stages of the drought but did not recruit successfully the following year, despite a return to higher‐than‐baseflow conditions. This ‘lag effect’ in response to drought emphasises the value of long‐term survey data. Although changes in faunal composition were inconsistent among sites, marked shifts in taxa richness, abundance and trophic organisation after the riffle habitat dried provide evidence for a stepped response.
Responses by macroinvertebrate assemblages to droughts of differing severity in English chalk streams were variable. The prolonged 1988–92 drought had a greater impact than shorter droughts in the early 1970s but recovery over the next 3 years was swift. Effects of the 1995 summer drought were buffered by sustained groundwater discharge from the previous winter. These droughts tended to reduce available riverine habitats, especially via siltation, but few taxa were eliminated because they could recolonise from perennial sections of the chalk streams.
In the contrasting environments of the intermittent streams studied in England and Australia, there are parallels in the rapid rates of recolonisation. However, recruitment by taxa that lack desiccation‐resistant stages or have limited mobility is delayed. Currently, long‐term data on these systems may be insufficient to indicate persistent effects of droughts or predict the impacts of excessive surface or groundwater abstraction or the increased frequency and duration of droughts expected with global climate change.
Causes and consequences of long‐term climatic variability on the Australian continent
Authors: Kershaw Peter , Moss Patrick , Van Der Kaars Sander 
Published: June 2003

Summary 1. Ice‐volume forced glacial–interglacial cyclicity is the major cause of global climate variation within the late Quaternary period. Within the Australian region, this variation is expressed predominantly as oscillations in moisture availability. Glacial periods were substantially drier than today with restricted distribution of mesic plant communities, shallow or ephemeral water bodies and extensive aeolian dune activity.2. Superimposed on this cyclicity in Australia is a trend towards drier and/or more variable climates within the last 350 000 years. This trend may have been initiated by changes in atmospheric and ocean circulation resulting from Australia's continued movement into the Southeast Asian region and involving the onset or intensification of the El Niño‐Southern Oscillation system and a reduction in summer monsoon activity.3. Increased biomass burning, stemming originally from increased climatic variability and later enhanced by activities of indigenous people, resulted in a more open and sclerophyllous vegetation, increased salinity and a further reduction in water availability.4. Past records combined with recent observations suggest that the degree of environmental variability will increase and the drying trend will be enhanced in the foreseeable future, regardless of the extent or nature of human intervention.
Effects of drought on fish across axes of space, time and ecological complexity
Authors: Matthews William J. , Marsh‐Matthews Edie 
Published: June 2003

SummaryWe evaluate the position of 50 previously published studies of fish and drought with respect to spatial scale of study (individual stream pools to subcontinents), length of the dry period (weeks to centuries), and level of system complexity (individual fish to ecosystems). Most papers address short (months to a year) droughts or dry periods, in local reaches of streams, and impacts on populations or local assemblages. In these 50 papers, the most frequently demonstrated effects of drought were population declines, loss of habitat, changes in the community, negative effects from changes in water quality, movement within catchments, and crowding of fish in reduced microhabitats. Thirteen other less frequent effects also were identified.Gaps in knowledge exist on effects of long‐term droughts (decades to centuries), influence of drought on fish effects in ecosystems, and at the spatial scale of river basins to subcontinents. However, some of these gaps have recently been addressed, particularly additive effects of repeated drying episodes and whole‐lake or basin‐wide effects of drought, and in using molecular techniques to seek signals of drought at wide geographic scales because of events in the deep past. Gaps in knowledge remain for effects of very short dry periods, on drought effects on higher levels of complexity, and on the manner in which droughts at the scale of decades affect fish.Data from streams in Oklahoma and elsewhere in the south‐western U.S.A. suggest that most droughts may leave little persistent signal in the existing fish fauna, i.e. that recovery from drought by fish populations or assemblages in the region can be rapid. However, species that are vulnerable to drought or water loss in streams may have disappeared from some basins in the region before the mid‐1900s, and recent evidence also suggests that extreme droughts do sometimes alter fish assemblages.Little is known about mechanisms by which droughts have direct or indirect effects on fish, the roles of droughts in the evolution of fish species, and the ways droughts alter effects of fish in ecosystems. Global climate changes may have serious consequences for future local or regional fish faunas, but ongoing studies of fish experiencing drought may aid in future conservation of what will become species at risk under climate‐change scenarios.
The role of refugia for fishes during drought: a review and synthesis
Authors: Magoulick Daniel D. , Kobza Robert M. 
Published: June 2003

Summary

Drought is a natural disturbance of aquatic ecosystems and can be a major factor in structuring aquatic communities. For individuals, populations and communities to persist in disturbed environments, they must have refuge from disturbance or disturbance must be minimal. Refugia convey spatial and temporal resistance or resilience in the face of disturbance, but the role of refugia in aquatic systems remains poorly understood.2. We review available literature on aquatic refugia for fishes in order to synthesise current knowledge and provide suggestions for needed research. Our objectives were to clarify definitions of disturbance and refugia in the context of drought in aquatic systems, review how refuge habitats influence fish community structure, and consider the potential impact of refugia on fish population and community dynamics during drought.3. Droughts cause a decrease in surface area/volume and an increase in extremes of physical and chemical water quality parameters. These conditions are linked with biotic interactions that structure the community of fishes residing in low‐flow or dry season refugia by increasing mortality rates, decreasing birth rates and/or increasing migration rates. Many aquatic organisms seek refuge from disturbance and/or have adaptations (e.g. physiological tolerance) that provide refuge.4. Drought in aquatic systems leads to shifts in refugia spacing and connectance at multiple spatial and temporal scales. Refuge size, disturbance intensity, and mobility of organisms is predicted to play a large role in population persistence. We expect that refuge habitats will experience net immigration during drying and net emigration after rewetting, with the opposite occurring in surrounding habitat patches. Population dynamics of fishes using refugia during drought are best modelled by modified source‐sink dynamics, but dynamics are likely to change with spatial scale.
Drought and aquatic ecosystems: an introduction
Authors: Humphries Paul , Baldwin Darren S. 
Published: June 2003

Summary

1. This paper introduces, and summarises the key messages of, a series of papers that emanated from a symposium on the Role of Drought in the Ecology of Aquatic Systems, held in Australia in 2001.2. Defining drought hydrologically is problematic because the return times, intensity, duration and long‐term trends in low‐flow periods are specific to regions and times. Droughts may instead be referred to as ‘significant low‐flow periods’, many of which have been replaced by ‘anti‐drought’ conditions in rivers as they are used increasingly as irrigation conduits.3. Droughts can be divided into those that cause predictable, seasonal press disturbances and less predictable, protracted ‘ramp’ disturbances. However, while droughts may be ‘ramp’ disturbances, their effects on aquatic biota are most likely to be ‘stepped’ when geomorphological or hydrological thresholds are crossed, causing abrupt changes in biological community structure and ecosystem processes.4. Physical, morphological, physiological or behavioural refugia confer resistance or resilience to riverine populations and communities that experience drought conditions. The physical and chemical parameters associated with refugia habitats and their formation, influence population parameters within, and interactions among, species and can have protracted reproductive consequences, even well after the cessation of the drought.5. Fish, invertebrate and plant populations and assemblages seem to recover rapidly from drought. Most studies of the effects of drought, however, have arisen fortuitously and have involved relatively short temporal, and small spatial, scales. Innovative approaches, such as microsatellite DNA analyses, can reveal that the effects of drought may be profound and long‐lasting, resulting in population bottlenecks and altering the course of the evolution of species.6. During periods of drought, decreases in inputs of dissolved organic carbon, nitrogen and phosphorus may lead to carbon limitation to microbial metabolism, resulting in autotrophic production being favoured over heterotrophic production.7. Long‐term climate trends, as indicated by palaeoecological evidence, suggest that, at least for Australia, droughts are likely to occur more frequently in the future. Anthropogenic effects on climate are likely to exacerbate this.8. It is important that drought is seen for what it is: a natural extreme of the flow continuum, with flooding at the other extreme. Thus, despite the potential for dramatic impacts on aquatic biota and the negative social connotations associated with such events, drought must be incorporated into river management plans.
Effects of extreme low flows on freshwater shrimps in a perennial tropical stream
Authors: Covich A.P. , Crowl T.A. , Scatena F.N. 
Published: June 2003

Summary

Long‐term data on rainfall suggests that perennial rainforest streams rarely are subject to drying of riffles or pools in the wet, non‐seasonal Caribbean climate of Puerto Rico. Unusually low rainfall in 1994 caused some headwater riffles to dry out completely, resulting in isolated pools, reduced pool volumes and loss of access to microhabitats by benthic invertebrates.
From 1992 to 1998, shrimp populations were sampled bimonthly using baited traps in six pools along 1200 m (from 305 to 480 m in altitude) of Quebrada Prieta, a second‐order headwater stream in the Luquillo Experimental Forest (Caribbean National Forest).
Following contraction of the smaller and shallower pools in the most upstream section of the stream, mean densities of the dominant shrimp (Atya lanipes) increased from 22 to 75 shrimp m−2 of pool area during the 1994 drought year. A second common species (Xiphocaris elongata) increased from 5 to 14 shrimp m−2. A smaller percentage of adults of both species was gravid during the drought.
Following the 1994 drought (1995–1998), densities of both shrimp species and reproductive activity of Atya returned to predrought (1990–1993) levels. However, the reproductive activity of Xiphocaris remained lower than in the predrought period.
It is suggested that prolonged droughts, even in tropical rainforest biomes, may significantly alter aquatic communities through localised crowding effects resulting from habitat contraction, and lead to prolonged decreases in reproductive output. Consequently, major alterations in aquatic populations and communities would be predicted by current climate change scenarios of decreased total rainfall and increased variability.
Protection against atypical furunculosis in Atlantic halibut, Hippoglossus hippoglossus (L.); comparison of a commercial furunculosis vaccine and an autogenous vaccine
Authors: Gudmundsdóttir S , Lange S , Magnadóttir B , Gudmundsdóttir B K 
Published: June 2003

AbstractAtlantic halibut, Hippoglossus hippoglossus (L.), was shown to be sensitive to infection by three different isolates of Aeromonas salmonicida ssp. achromogenes in pre‐challenge tests using intraperitoneal (i.p.) and intramuscular (i.m.) injections as well as bath challenges. A commercial furunculosis vaccine, Alphaject 1200, and an autogenous vaccine, AAS, based on the challenge strain, induced immune protection as shown in challenge tests 8 weeks post‐immunization. The survival rate of vaccinated fish after i.p. challenge was 100%, whereas mortality of control fish was 61%. Employing i.m. challenge, relative percentage survival induced by the furunculosis vaccine and the AAS vaccine was 47 and 44, respectively. Mortality of i.m. injected controls was 68%. Vaccinated fish behaved normally following vaccination but the weight gain was significantly reduced in vaccinated fish 8 weeks post‐vaccination compared with control fish receiving phosphate‐buffered saline. At the same time, intra‐abdominal adhesions were observed in fish injected with either of the two vaccines or adjuvant alone. Antibody response against A. salmonicida ssp. achromogenes was detected in sera from fish receiving either vaccine.