Fatty acids reveal aquaculture and drought effects on a large tropical reservoir.

Fatty acids (FAs) and their metrics have been used to detect and assess the impacts of urbanization and agriculture on aquatic ecosystems. Here, we investigated whether seston FAs are also useful to characterize and understand early-stage aquaculture impacts in a large tropical reservoir (Furnas Reservoir, SE Brazil). We tested the hypothesis that single FAs, as well as selected FA metrics in the seston fraction, are efficient markers of net-cage fish farming effects. In general, fish farming had only minor effects on standard water chemical variables, mainly small increases in ammonium, nitrate, and dissolved organic nitrogen concentrations. By increasing concentrations of several polyunsaturated FAs, early-stage fish farming improved sestonic food quality in the more oligotrophic branch of the reservoir under drought conditions. However, in general, increases in concentrations of bacterial FAs, due to fish farming, suggested organic matter (OM) subsidies from non-ingested and non-assimilated fish feed. In the more eutrophic reservoir branch, seston FA profiles suggested that fish farming caused an increase of low-quality food resources, such as cyanobacteria. Thus, background impact levels may determine the biochemical responses of tropical reservoirs to fish farming. Higher contributions of potentially sewage-derived and bacterial FAs during drought conditions, especially at reference sites of the more oligotrophic branch, suggested that drought shifted OM inputs towards anthropogenic sources, thereby overwriting land-use related differences between reservoir branches and homogenizing their environmental conditions. In conclusion, FA variables were useful to evaluate and understand environmental conditions, as well as the effects of early-stage fish farming and drought, and should be considered in impact assessments in tropical lentic ecosystems.

Impacts of fish farming on elemental stoichiometry, fluorescence components, and stable isotopes of dissolved organic matter in a tropical reservoir.

Aquaculture impacts on aquatic organic matter and ecosystem integrity are poorly understood, especially in tropical regions. Here, we investigated the impacts of Nile tilapia net cage farming on the elemental stoichiometry, fluorescence components, and stable isotopes of dissolved organic matter (DOM) of the large, tropical Furnas Reservoir (SE Brazil). Early-stage fish farming, i.e., relatively small and recently implemented farms, had detectable incipient effects on DOM characteristics, and these effects differed between reservoir branches. In the less eutrophic Rio Grande branch of the reservoir, we found a reduction in natural humic-like DOM components and an increase in a protein-like DOM component as far as 100 m away from fish farms. Further, we observed a decrease in δ15N-TDN due to fish farming. In the more eutrophic Rio Sapucaí branch, there were only local decreases in C:N ratios, as well as rises in C:P and N:P of DOM due to fish farming. These results suggest that early-stage fish farming had local but detectable effects on aquatic DOM that depended on previous eutrophication levels and highlight the need to assess the early impacts of fish farming on tropical reservoirs by combining different monitoring strategies.

Land-use impacts on fatty acid profiles of suspended particulate organic matter along a larger tropical river.

Land-use change, such as agricultural expansion and urbanization, can affect riverine biological diversity and ecosystem functioning. Identifying the major stressors associated with catchment land-use change is a prerequisite for devising successful river conservation and restoration strategies. Here, we analyzed land-use effects on the fatty acid (FA) composition and concentrations in suspended particulate organic matter (SPOM) along a fourth-order tropical river, the Rio das Mortes. Thereby, we aimed at testing the potential of fatty acids in riverine suspended particulate organic matter (SPOM-FAs) as indicators of land-use change in tropical catchments, and at identifying major human impacts on the biochemical composition of SPOM, which represents an important basal energy and organic matter resource for aquatic consumers. River water SPOM and total FA concentrations ranged between 2.8 and 10.2mg dry weight(DW)L(-1) and between 130.6 and 268.2µg DW L(-1), respectively, in our study. Urbanization was the only land-use category correlating with both FA composition and concentrations, despite its low contribution to whole catchment (1.5-5.6%) and riparian buffer land cover (1.7-6.6%). Higher concentrations of saturated FAs, especially C16:0 and C18:0, which are the main components of domestic sewage, were observed at sampling stations downstream of urban centers, and were highly correlated to urbanization, especially within the 60m riparian buffer zone. Compared to water chemical characteristics (inorganic nutrients, dissolved oxygen, pH, and specific conductance) and river habitat structural integrity, FA variables exhibited a higher variability along the investigated river and were more strongly correlated to urban land use, suggesting that SPOM-FA profiles may be an efficient indicator of urban land-use impacts on larger tropical rivers. High total FA concentrations in the SPOM of urbanized tropical rivers may represent high-energy biochemical subsidies to food webs, potentially leading to changes in functional ecosystem characteristics, such as bacterial and suspension-feeder production.

Sterol composition of freshwater algivorous ciliates does not resemble dietary composition.

Algivorous ciliates represent an important link in freshwater food webs, as they transfer energy and biochemical matter from their algal prey to mesozooplankton predators. However, it is still unknown how dietary composition influences the biochemical composition of ciliates. We analyzed the sterol composition of the algivorous ciliates Balanion planctonicum and Urotricha farcta and compared it to the sterol composition of their diet--the cryptomonad Cryptomonas phaseolus. The sterol composition of the ciliates did not resemble that of their algal diet. Ergosterol [(22E)-ergosta-5,7,22-trien-3beta-ol] was the sterol in highest concentration in C. phaseolus, whereas stigmasterol [(24S)-24-ethylcholesta-5,22E-dien-3beta-ol] was dominant in both B. planctonicum and U. farcta. Moreover, the occasionally higher sterol concentrations in the ciliates than in their algal diet suggest sterol accumulation by the ciliates. We conclude that dietary sterol composition influences the composition of the two algivorous ciliates studied, but species-specific differences in metabolism probably determine the ultimate sterol composition of the ciliates.

Factors affecting biochemical composition of seston in an eutrophic reservoir (Pampulha Reservoir, Belo Horizonte, MG).

Sestonic biochemical composition (lipids, proteins and carbohydrates) may change with varying environmental fluctuations. These changes and the effects in the nutritional status of algae consists of an actual increasing source of interest. The aims of this work were to establish the relationship between biochemical composition of seston and 1) a range of physical, chemical and climatological factors, and 2) the natural fluctuation in the species composition in phytoplankton assemblages of the Pampulha Reservoir, an urban eutrophic lake located in Belo Horizonte, MG. Seasonal changes in the biochemical composition were observed in this study. None of the considered abiotic factors alone seem to affect the biochemical composition. So the effects could only be understood by interactions among different environmental factors. On the other hand, the dominant algal groups probably have some influence in the observed changes in biochemical composition of seston.

Diminished linear growth during intermittent calcitriol therapy in children undergoing CCPD.

Daily calcitriol therapy has been reported to improve linear growth in children with renal bone disease, and 1,25-dihydroxyvitamin D is a key regultor of chondrocyte proliferation and differentiation. Whereas large intermittent doses of calcitriol can lower serum parathyroid hormone (PTH) levels and reverse the skeletal changes of secondary hyperparathyroidism, the impact of intermittent calcitriol therapy on linear growth in children is not known. Thus, we studied 16 pre-pubertal patients with bone biopsy-proven secondary hyperparathyroidism who completed a 12-month prospective clinical trial of intermittent calcitriol therapy. Biochemical results and growth data obtained during intermittent calcitriol therapy were compared to values determined during the preceding 12 months of daily calcitriol therapy in each study subject; changes in bone histology were assessed after one year of intermittent calcitriol therapy. Z-scores for height did not change during 12 months of daily calcitriol therapy. Although the skeletal lesions of secondary hyperparathyroidism improved in most patients, Z-scores for height decreased from -1.8 +/- 0.32 to -2.0 +/- 0.33, P < 0.01, during intermittent calcitriol therapy. The largest reductions were seen in patients who developed adynamic bone lesions after 12 months of treatment. Delta Z-scores for height correlated with serum PTH, r = 0.71, P < 0.01, and alkaline phosphatase levels, r = 0.67, P < 0.01, during intermittent calcitriol therapy but not during daily calcitriol therapy. The data suggest that high dose intermittent calcitriol therapy adversely affects linear growth, particularly in patients with the adynamic lesion. The higher doses of calcitriol or the intermittent schedule of calcitriol administration may directly inhibit chondrocyte activity within growth plate cartilage of children with end-stage renal disease.

Renal ultrasound abnormalities in children with end-stage liver disease--reversal by liver transplantation.

Ultrasound (US) imaging of the kidneys was performed in 43 pediatric patients with end-stage liver disease evaluated for orthotopic liver transplantation. Renal size was increased in 8 patients (19%) and echogenicity of the kidneys was increased in 12 patients (28%). In 12 patients studied after liver transplantation, US revealed normal renal size in all and increased echogenicity in only 2 patients shortly after transplantation. Normalization of renal US findings was also found in 2 patients studied before and after liver transplantation. The glomerular filtration rate varied from 65 to 225 ml/min per 1.73 m2 in 5 patients with abnormal US, and from 74 to 116 ml/min per 1.73 m2 in 3 patients with normal US. Nephromegaly and increased echogenicity on renal US are frequent in children with end-stage liver disease and appear to be mostly reversible by liver transplantation.

Infantile hepatic hemangiomas. Clinical features, radiologic investigations, and treatment of 20 patients.

The clinical features, radiologic investigation, and treatment of 20 infants with hepatic hemangiomas are presented. Palpable abdominal mass (n = 18) and cardiac failure (n = 11) were the common presenting features. Nine patients had hyperconsumptive coagulopathy. Seven patients had other hemangiomas. Ultrasound (n = 15) showed the number and distribution of the hemangiomas within the liver. Hypoechoic and hyperechoic elements were present in addition to prominent vascular channels and diminished caliber of the distal aorta. Radionuclide sulfur colloid (n = 12) and labeled red blood cell (n = 7) studies showed the distribution and vascularity of the hemangiomas. Computed tomography (n = 8) revealed central hypointensity with marked peripheral enhancement after contrast. Arteriography now performed only as a prelude to therapeutic embolization demonstrated hypervascularity in each patient, contrast pooling in six and early draining veins in five. Magnetic resonance scanning (n = 3) showed decreased signal intensity on T1 images and high intensity signal on T2. In two patients, there was resolution or improvement of the hemangiomas without therapy. Four patients had surgery (lobectomy [2], trisegmentectomy [1], and surgical evacuation of a central hematoma [1]). Steroids and radiation were given to seven patients, and one patient also required therapeutic embolization. Steroids were the initial therapy in five patients, one of whom later required therapeutic embolization and another cyclophosphamide. Two patients were treated initially with radiation therapy, one of whom also needed emergency hepatic artery ligation. Seventeen of the 20 patients are alive and well from 6 months to 14 years after diagnosis.

Five years' experience with continuous ambulatory or continuous cycling peritoneal dialysis in children.

In 93 children, end-stage renal disease was treated with the new dialytic methods of continuous ambulatory peritoneal dialysis (CAPD) or continuous cycling peritoneal dialysis (CCPD) over 5 years. Modality survival rates at 36 months with CAPD, CCPD, or both were 20%, 93%, and 87%, respectively. Use of CCPD as the primary dilaytic method increased during the study period. The peritonitis rate was one episode per 11.8 patient treatment months and was similar with both CAPD and CCPD. Gram-positive organisms were cultured in 34% of these episodes of peritonitis. Staphylococcus aureus peritonitis was associated with a recurrence rate of 40% and led to catheter replacement in 45% of the episodes. Peritoneal membrane failure necessitating switching to hemodialysis was related to peritonitis in three patients. Of the 74 peritoneal catheters that required replacement, 70% were infected. Serial serum levels of urea nitrogen, potassium, calcium, phosphorus, albumin, and alkaline phosphatase remained stable, whereas serum creatinine level rose slightly over time. Episodes of hyperkalemia, hypercalcemia, and hyperphosphatemia were observed at a frequency of one episode per 12.2, 4.6, and 2.5 treatment months, respectively. Blood transfusions were required in once per 1.5 and 3.3 treatment months in seven anephric patients and in 35 patients with their own kidneys, respectively (P = 0.05). In prepubertal patients who received CAPD or CCPD for greater than 1 year, little or no improvement in growth occurred in relationship to either chronologic or bone age.

Scoliosis after thoracotomy for esophageal atresia.

Progressive scoliosis was seen in eight children after thoracotomy for esophageal atresia. Postoperatively, all had had severe mediastinitis and empyema secondary to dehiscence of the esophageal anastomosis and required reoperation. Healing was accompanied by marked scarring and rib fusion; with growth, a scoliosis developed with the concavity toward the thoracotomy site. Most spinal curvatures appeared years after the thoracotomy and progressed rapidly at the time of adolescent growth spurt. Excision of fused ribs, spinal fusion, and instrumentation led to improvement in four patients.