In vitro androgenicity in pulp and paper mill effluents

Pulp and paper mill effluents were examined for in vitro androgenicity using a recombinant yeast-based androgen receptor assay. Low levels of androgenic effects were detected in extracts of some effluents after activated sludge treatment. Yeast cell growth cell was inhibited in some samples, and this interfered with the androgenic response. Solid-phase fractionation revealed androgenicity after partial separation of components in the effluents. Comparison of levels in untreated effluent and in effluent treated in an aerated lagoon showed that this treatment had only a marginal effect on androgenicity. An assay of the fractions eluted with increasing concentrations of methanol showed that androgenic compounds were low to moderately lipophilic. In an attempt to identify these compounds, a number of wood-related compounds (guaiacol, vanillin, beta-sitosterol, betulin, pinosylvin-O-methyl ether, and a wood extract enriched in lignans) were examined but were found not to be androgenic. Raw process water was not androgenic, but water from a highly humified lake and process water from the production of pulp from partly decayed wood had low androgenicity. It therefore can be plausibly suggested that the androgens originated in decaying wood. An assay of androgenicity in the bile of juvenile rainbow trout exposed to effluents for 3 weeks showed increased dose-dependent levels of androgens after enzymatic hydrolysis of hormone conjugates.     

In vitro and in vivo comparisons of fish-specific CYP1A induction relative potency factors for selected polycyclic aromatic hydrocarbons

Induction of cytochrome P450 (CYP1A), as measured by liver ethoxyresorufin-O-deethylase (EROD) activity in juvenile rainbow trout (Oncorhynchus mykiss), was used to derive relative potency factors (RPFs) for several polycyclic aromatic hydrocarbons (PAHs), chosen for their induction potency in a rainbow trout liver cell line (RTL-W1). Potency for causing induction was estimated as the median effective concentration (EC50) from exposure-response curves. With the exception of phenanthrene, all PAHs tested induced EROD activity in juvenile trout, ranked as: benzo[k]fluoranthene>benzo[b]fluoranthene>benzo[b]fluorene>beta-napthoflavone>retene (7-isopropyl-1-methylphenanthrene). When induction potency was expressed relative to benzo[k]fluoranthene, RPFs ranged from 0.02 to 1, and the rank order in vivo was identical to the rank order with RTL-W1-derived values. The additivity of PAHs in mixtures in RTL-W1 cells was compared to whole-fish results from a previous study. EROD induction showed additive interactions for PAHs with exposure-response curves of similar slopes. This study demonstrates that assays of CYP1A induction using rainbow trout liver cells in culture would be a convenient substitute for assays with whole fish as part of testing programs for risk assessment of PAHs.     

The effect of social interactions on circadian self-feeding rhythms in rainbow trout Oncorhynchus mykiss Walbaum

Circadian feeding rhythms have been revealed in several fish species, but whether or not social interactions influence the expression of the rhythms remains largely unexplored. This paper reported such an exploration in rainbow trout. The experiment was conducted in two consecutive stages in two adjacent insulated rooms. In Stage 1, 40 fish (146.0+/-21.7 g, mean+/-S.D.) were held individually in Room 1. In Stage 2, those 40 fish from Room 1 were distributed into eight groups of five fish according to their previous circadian properties and placed in Room 2. Isolated trout were generally diurnal feeders, but variability among the individuals was evident, with five types of diurnal self-feeding pattern being detected. The influence of social interactions on diel self-feeding pattern in a group was found to be temporary and reversible. The grouping process did not necessarily enhance the expression of circadian self-feeding rhythms, and the dominant individual(s) did not determine the properties of circadian self-feeding rhythms in the group.     

Modulation of catecholamine release and cortisol secretion by social interactions in the rainbow trout,Oncorhynchus mykiss

The objective of the present study was to investigate the effect of social status on the ability of rainbow trout to secrete the stress hormones, cortisol, and catecholamines. Rainbow trout were confined in pairs for six days to permit the formation of dominance hierarchies. An in situ saline-perfused posterior cardinal vein (PCV) preparation was then used to assess cortisol secretion or release of the catecholamine hormones, adrenaline and noradrenaline, in response to the inclusion of appropriate secretagogues in the perfusate. Fish identified as subordinate on the basis of their behaviour showed a characteristic elevation of circulating plasma cortisol concentrations when compared with dominant fish. When the interrenal cells were stimulated in situ with adrenocorticotropic hormone, subordinate fish displayed a significantly lower rate of cortisol secretion than dominant fish. However, social status had no significant effect on either adrenaline or noradrenaline secretion rates upon stimulation of the chromaffin cells in situ with acetylcholine. These results suggest that the chronic elevation of plasma cortisol associated with subordinate social status in rainbow trout reduces the sensitivity of the cortisol-secreting interrenal cells, presumably through negative feedback mechanisms.     

Metal accumulation and metallothionein in two populations of brown trout, Salmo trutta, exposed to different natural water environments during a run-off episode

Cd, Cu and Zn concentrations were measured in ambient water as well as in gills, liver and kidney tissues of two natural populations of brown trout (Salmo trutta) during a run-off episode in two rivers with different metal compositions due to mining pollution. Metallothionein (MT) was also measured in these tissues. The two rivers, Rugla (Cu contaminated) and Naustebekken (Cd and Zn contaminated), are located in two neighboring drainage basins separated by the topographic divide near the city of Røros in the County of Sør-Trøndelag, Norway. In Rugla, the Cu concentration increased from 15 μg/l at the low water level to 41 μg/l during the run-off episode. In Naustebekken, corresponding values for Cd were 90–170 ng/l and those for Zn were 49–91 μg/l. Gill concentrations of Cu and Cd/Zn MT in both populations of native trout clearly reflect the presence of these metals in the rivers during the run-off, in accordance with the hypothesis of protection caused by MT induction. When Rugla trout were transferred to Naustebekken and vice versa, both the amounts of MT itself and the Cu contents reflected the concentration of this metal in the new environment, indicating that MT induction also protects against acutely increased metal levels. The measured levels of MT in both native and transferred trout can account for all the Cd present in the tissues, but not for all of the Cu and Zn. The capacity of MT to regulate Cd and Cu in the trout populations in their natural habitat therefore seems clearly present. Our data also indicate that the MT I and II isoforms may bind metals selectively.     

Changing trends of neonatal and postneonatal deaths in very-low-birth-weight infants

Advances in perinatal care have resulted in a decline in mortality of very-low-birth-weight infants (<1.5 kilograms) and also in an extension of the mortality period. To determine the current relevance of neonatal mortality results as indicators of outcome, all deaths among 427 very-low-birth-weight infants admitted during 1975–1977 were documented. A total of 145 infants died; 90 of the deaths (62%) occurred during the early neonatal period (0 to 6 days), 35 (24%) in the late neonatal period (7 to 27 days), and 20 (14%) in the postneonatal period. Death in 17 of the 20 postneonatal losses was due to neonatal complications of prematurity, and 16 of the 20 deaths occurred during the initial hospitalization. The postponement of these deaths to the postneonatal period has important epidemiologic implications and indicates a need for a reconsideration of accepted reporting mechanisms for infants of very low birth weight.     

The effect of a low continuous positive airway pressure on the reflex control of respiration in the preterm infant

The airway occlusion technique was used to measure the strength of the Hering-Breuer inflation reflex before and during the administration of low pressure CPAP. In five of 12 preterm infants studied in the first two weeks of life, CPAP did not alter the inflation reflex. In the other seven premature infants, shortened rather than lengthened inspiratory efforts were observed on occlusion 32 times of CPAP but only twice on CPAP. In seven term infants at 1 to 2.5 hours of age this shortening was noted only twice in 58 occlusions. In the preterm infants exhibiting short responses, the peak inspiratory pressure generated in response to occlusion rose on CPAP from 3.4 to 7.1 cm H2O (p less than 0.005), while respiratory rate fell from 61 to 49 breaths/minute (p less than 0.025). This data suggests that CPAP enhances these infants' ability to adjust to increased respiratory loads, possibly by the elimination of a Hering-Breuer deflation reflex.     

Heat-stable enterotoxigenic Escherichia coli and necrotizing enterocolitis: lack of an association.

During an outbreak of diarrhea in a special care nursery caused by heat-stable enterotoxigenic Escherichia coli (serotype 078:H11:K80), nine (4.3%) of the 205 infants in the nursery developed necrotizing enterocolitis. Cases of necrotizing enterocolitis were not significantly more common in infants colonized or infected with these organisms; heat-stable enterotoxigenic E. coli was isolated from 5(56%) of nine cases of necrotizing ecterocolitis and from 27(38%) of the 71 infants without necrotizing enterocolitis who were also cultured. Our findings suggest that caution should be taken in implicating enterotoxigenic E. coli as a cause of necrotizing enterocolitis.     

Diagnosis of exocrine pancreatic insufficiency in cystic fibrosis by the synthetic peptide N-benzoyl-L-tyrosyl-p-aminobenzoic acid.

The synthetic peptide N-benzoyl-L-tyrosyl-p-aminobenzoic acid is specifically cleaved by chymotrypsin to Bz-Ty and PABA. The liberated PABA is absorbed and excreted in the urine. Accordingly, PABA recovery reflects intraluminal chymotrypsin activity and is an index of exocrine pancreatic function. This test was evaluated in 24 patients with cystic fibrosis to determine its role in the diagnosis of exocrine pancreatic insufficiency. Cumulative percent PABA recovery in six hours was significantly lower in CF patients compared with the control group. No overlap was noted between the two groups. There was good correlation between PABA recovery, fecal chymotrypsin activity, and coefficient of fat absorption. These findings indicate that PABA recovery is significantly reduced in patients with CF and steatorrhea and may prove a practical and reliable test of pancreatic insufficiency.