Feeding manipulation elicits different proliferative responses in the gastrointestinal tract of suckling and weanling rats

Food deprivation has been found to stimulate cell proliferation in the gastric mucosa of suckling rats, whereas the weanling period has been reported to be unresponsive in terms of proliferative activity. In the present study we analyze regional differences in the effect of milk or food deprivation on cell proliferation of the epithelia of the esophagus and of five segments of small intestine in suckling, weanling and newly weaned Wistar rats of both sexes. DNA synthesis was determined using tritiated thymidine to obtain labeling indices (LI); crypt depth and villus height were also determined. Milk deprivation decreased LI by 50% in the esophagus (from 15 to 8.35%) and small intestine (from 40 to 20%) of 14-day-old rats. In 18-day-old rats, milk and food deprivation decreased LI in the esophagus (from 13 to 5%) and in the distal segments of the small intestine (from 36-40 to 24-32%). In contrast, the LI of the epithelia of the esophagus (5%) and of all small intestine segments (around 30%) of 22-day-old rats were not modified by food deprivation. Crypt depth did not change after treatment (80 to 120 µm in 14- and 22-day-old rats, respectively). Villus height decreased in some small intestine segments of unfed 14- (from 400 to 300 µm) and 18-day-old rats (from 480 to 360 µm). The results show that, contrary to the stomach response, milk deprivation inhibited cell proliferation in the esophagus and small intestine of suckling rats, demonstrating the regional variability of each segment of the gastrointestinal tract in suckling rats. In newly weaned rats, food deprivation did not alter the proliferation of these epithelia, similarly to the stomach, indicating that weanling is a period marked by the insensitivity of gastrointestinal epithelia to dietary alterations

Relation of the disaccharidases in the small intestine of the rat to the degree of experimentally induced iron-deficiency anemia

Hypolactasia associated with severe iron-deficiency anemia has been reported in several studies. The objective of the present study was to determine whether hypolactasia is associated with the degree and duration of iron-deficiency anemia. Newly weaned male Wistar rats were divided into a control group receiving a diet supplemented with iron (C) and an experimental group (E) receiving a diet not supplemented with iron (iron-deficiency diet). The animals were studied on the 3rd, 5th, 7th, 14th, 21st, 28th and 35th days of the experiment, when overall and iron nutritional status and disaccharidase activity in the small intestine were determined by the Dahlqvist method. A reduction in weight occurred in the anemic animals starting on the 5th day of the study. Anemia was present in the experimental animals, with a progressive worsening up to the 14th day (hemoglobin: C = 13.27 and E = 5.37) and stabilizing thereafter. Saccharase and maltase activities did not differ significantly between groups, whereas lactase showed a significant reduction in total (TA) and specific activity (SA) in the anemic animals starting on the 21st day of the study. Median lactase TA for the C and E groups was 2.27 and 1.25 U on the 21st day, 2.87 and 1.88 U on the 28th day, and 4.20 and 1.59 U on the 35th day, respectively. Median lactase SA was 0.31 and 0.20 U/g wet weight on the 21st day, 0.39 and 0.24 U/g wet weight on the 28th day, and 0.42 and 0.23 U/g wet weight on the 35th day, respectively. These findings suggest a relationship between the enzymatic alterations observed and both the degree and duration of the anemic process. Analysis of other studies on intestinal disaccharidases in anemia suggests that the mechanism of these changes may be functional, i.e., that the enterocytes may suffer a reduction in their ability to synthesize these enzymes.

Pancreatic nitric oxide and oxygen free radicals in the early stages of streptozotocin-induced diabetes mellitus in the rat

The objective of the present study was to explore the regulatory mechanisms of free radicals during streptozotocin (STZ)-induced pancreatic damage, which may involve nitric oxide (NO) production as a modulator of cellular oxidative stress. Removal of oxygen species by incubating pancreatic tissues in the presence of polyethylene glycol-conjugated superoxide dismutase (PEG-SOD) (1 U/ml) produced a decrease in nitrite levels (42%) and NO synthase (NOS) activity (50%) in diabetic but not in control samples. When NO production was blocked by N G-monomethyl-L-arginine (L-NMMA) (600 µM), SOD activity increased (15.21 ± 1.23 vs 24.40 ± 2.01 U/mg dry weight). The increase was abolished when the NO donor, spermine nonoate, was added to the incubating medium (13.2 ± 1.32). Lipid peroxidation was lower in diabetic tissues when PEG-SOD was added (0.40 ± 0.02 vs 0.20 ± 0.03 nmol/mg protein), and when L-NMMA blocked NOS activity in the incubating medium (0.28 ± 0.05); spermine nonoate (100 µM) abolished the decrease in lipoperoxide level (0.70 ± 0.02). We conclude that removal of oxygen species produces a decrease in pancreatic NO and NOS levels in STZ-treated rats. Moreover, inhibition of NOS activity produces an increase in SOD activity and a decrease in lipoperoxidation in diabetic pancreatic tissues. Oxidative stress and NO pathway are related and seem to modulate each other in acute STZ-induced diabetic pancreas in the rat.

Rapid eye movement sleep deprivation induces an increase in acetylcholinesterase activity in discrete rat brain regions

Some upper brainstem cholinergic neurons (pedunculopontine and laterodorsal tegmental nuclei) are involved in the generation of rapid eye movement (REM) sleep and project rostrally to the thalamus and caudally to the medulla oblongata. A previous report showed that 96 h of REM sleep deprivation in rats induced an increase in the activity of brainstem acetylcholinesterase (Achase), the enzyme which inactivates acetylcholine (Ach) in the synaptic cleft. There was no change in the enzyme's activity in the whole brain and cerebrum. The components of the cholinergic synaptic endings (for example, Achase) are not uniformly distributed throughout the discrete regions of the brain. In order to detect possible regional changes we measured Achase activity in several discrete rat brain regions (medulla oblongata, pons, thalamus, striatum, hippocampus and cerebral cortex) after 96 h of REM sleep deprivation. Naive adult male Wistar rats were deprived of REM sleep using the flower-pot technique, while control rats were left in their home cages. Total, membrane-bound and soluble Achase activities (nmol of thiocholine formed min-1 mg protein-1) were assayed photometrically. The results (mean ± SD) obtained showed a statistically significant (Student t-test) increase in total Achase activity in the pons (control: 147.8 ± 12.8, REM sleep-deprived: 169.3 ± 17.4, N = 6 for both groups, P<0.025) and thalamus (control: 167.4 ± 29.0, REM sleep-deprived: 191.9 ± 15.4, N = 6 for both groups, P<0.05). Increases in membrane-bound Achase activity in the pons (control: 171.0 ± 14.7, REM sleep-deprived: 189.5 ± 19.5, N = 6 for both groups, P<0.05) and soluble enzyme activity in the medulla oblongata (control: 147.6 ± 16.3, REM sleep-deprived: 163.8 ± 8.3, N = 6 for both groups, P<0.05) were also observed. There were no statistically significant differences in the enzyme's activity in the other brain regions assayed. The present findings show that the increase in Achase activity induced by REM sleep deprivation was specific to the pons, a brain region where cholinergic neurons involved in REM generation are located, and also to brain regions which receive cholinergic input from the pons (the thalamus and medulla oblongata). During REM sleep extracellular levels of Ach are higher in the pons, medulla oblongata and thalamus. The increase in Achase activity in these brain areas after REM sleep deprivation suggests a higher rate of Ach turnover.

Changes in the fecal concentrations of cortisol and androgen metabolites in captive male jaguars (Panthera onca) in response to stress

In the present study we determined the efficacy of the measurement of fecal cortisol and androgen metabolite concentrations to monitor adrenal and testicular activity in the jaguar (Panthera onca). Three captive male jaguars were chemically restrained and electroejaculated once or twice within a period of two months. Fecal samples were collected daily for 5 days before and 5 days after the procedure and stored at -20ºC until extraction. Variations in the concentrations of cortisol and androgen metabolites before and after the procedure were determined by solid phase cortisol and testosterone radioimmunoassay and feces dry weight was determined by drying at 37ºC for 24 h under vacuum. On four occasions, fecal cortisol metabolite levels were elevated above baseline (307.8 ± 17.5 ng/g dry feces) in the first fecal sample collected after the procedure (100 to 350% above baseline). On one occasion, we did not detect any variation. Mean (± SEM) fecal androgen concentration did not change after chemical restraint and electroejaculation (before: 131.1 ± 26.7, after: 213.7 ± 43.6 ng/g dry feces). These data show that determination of fecal cortisol and androgen metabolites can be very useful for a noninvasive assessment of animal well-being and as a complement to behavioral, physiological, and pathological studies. It can also be useful for the study of the relationship between adrenal activity and reproductive performance in the jaguar.

Role of the caudal pressor area in the regulation of sympathetic vasomotor tone

It is well known that the ventrolateral medulla contains neurons involved in the tonic and reflex control of the cardiovascular system. Two regions within the ventrolateral medulla were initially identified: the rostral ventrolateral medulla (RVLM) and the caudal ventrolateral medulla (CVLM). Activation of the RVLM raises arterial blood pressure and sympathetic nerve activity, and activation of the CVLM causes opposite effects. The RVLM premotor neurons project directly to sympathetic preganglionic neurons and are involved in the maintenance of resting sympathetic vasomotor tone. A significant proportion of tonic activity in the RVLM sympathetic premotor neurons is driven by neurons located in a third region of the ventrolateral medulla denominated caudal pressor area (CPA). The CPA is a pressor region located at the extreme caudal part of the ventrolateral medulla that appears to have an important role controlling the activity of RVLM neurons. In this brief review, we will address the importance of the ventrolateral medulla neurons for the generation of resting sympathetic tone related to arterial blood pressure control focusing on two regions, the RVLM and the CPA.

Toluene permeabilization differentially affects F- and P-type ATPase activities present in the plasma membrane of Streptococcus mutans

Streptococcus mutans membrane-bound P- and F-type ATPases are responsible for H+ extrusion from the cytoplasm thus keeping intracellular pH appropriate for cell metabolism. Toluene-permeabilized bacterial cells have long been used to study total membrane-bound ATPase activity, and to compare the properties of ATPase in situ with those in membrane-rich fractions. The aim of the present research was to determine if toluene permeabilization can significantly modify the activity of membrane-bound ATPase of both F-type and P-type. ATPase activity was assayed discontinuously by measuring phosphate release from ATP as substrate. Treatment of S. mutans membrane fractions with toluene reduced total ATPase activity by approximately 80% and did not allow differentiation between F- and P-type ATPase activities by use of the standard inhibitors vanadate (3 µM) and oligomycin (4 µg/mL). Transmission electron microscopy shows that, after S. mutans cells permeabilization with toluene, bacterial cell wall and plasma membrane are severely injured, causing cytoplasmic leakage. As a consequence, loss of cell viability and disruption of H+ extrusion were observed. These data suggest that treatment of S. mutans with toluene is an efficient method for cell disruption, but care should be taken in the interpretation of ATPase activity when toluene-permeabilized cells are used, because results may not reflect the real P- and F-type ATPase activities present in intact cell membranes. The mild conditions used for the preparation of membrane fractions may be more suitable to study specific ATPase activity in the presence of biological agents, since this method preserves ATPase selectivity for standard inhibitors.

Expression of MMP-2 and MMP-9 in the rat trigeminal ganglion during the development of temporomandibular joint inflammation

Orofacial pain is a prevalent symptom in modern society. Some musculoskeletal orofacial pain is caused by temporomandibular disorders (TMDs). This condition has a multi-factorial etiology, including emotional factors and alteration of the masticator muscle and temporomandibular joints (TMJs). TMJ inflammation is considered to be a cause of pain in patients with TMD. Extracellular proteolytic enzymes, specifically the matrix metalloproteinases (MMPs), have been shown to modulate inflammation and pain. The purpose of this investigation was to determine whether the expression and level of gelatinolytic activity of MMP-2 and MMP-9 in the trigeminal ganglion are altered during different stages of temporomandibular inflammation, as determined by gelatin zymography. This study also evaluated whether mechanical allodynia and orofacial hyperalgesia, induced by the injection of complete Freund's adjuvant into the TMJ capsule, were altered by an MMP inhibitor (doxycycline, DOX). TMJ inflammation was measured by plasma extravasation in the periarticular tissue (Evans blue test) and infiltration of polymorphonuclear neutrophils into the synovial fluid (myeloperoxidase enzyme quantification). MMP expression in the trigeminal ganglion was shown to vary during the phases of the inflammatory process. MMP-9 regulated the early phase and MMP-2 participated in the late phase of this process. Furthermore, increases in plasma extravasation in periarticular tissue and myeloperoxidase activity in the joint tissue, which occurred throughout the inflammation process, were diminished by treatment with DOX, a nonspecific MMP inhibitor. Additionally, the increases of mechanical allodynia and orofacial hyperalgesia were attenuated by the same treatment.

Lipid and protein oxidation in the internal part of italian type salami containing basil essential oil (Ocimum basilicum L.)

Different concentrations of basil essential oil (Ocimum basilicum L.) (0.19; 0.38; 0.75; 1.87; 3.75 and 6.00 mg.g-1) were evaluated in relation to their antioxidant activity using the DPPH&#9679; radical methodology. From the IC50 obtained data, the concentrations of 0.19; 0.38; 0.75; 1.87; 3.75; 6.00 and 12.00 mg.mL-1 were applied directly to the product and these were sensorially evaluated by the test of control difference. The concentrations related to the highest acceptability (0.19; 0.38 and 0.75 mg.g-1) were tested for antioxidant activity in the internal part of Italian type salami - during the processing and after 30 days of storage, in terms of lipid and protein oxidation. The oxidation of lipids was determined using the method of TBARS. The method of carbonyl compounds was employed for proteins oxidation. Five different formulations of salami were elaborated: blank (without the use of antioxidant); control (using sodium eritorbate as antioxidant); and adding 0.19; 0.38 and 0.75 mg.g-1 of basil essential oil. The product was kept between 25 ºC and 18 ºC and UR between 95% and 70%, for 28 days. Analyses were carried out on the processing day and after 2, 7, 14, 21 and 28 days, and also following 30 days of storage. The basil essential oil in vitro presented an antioxidant activity of IC50 12 mg.mL-1. In the internal part of the Italian type salami the commercial antioxidant (control) and the formulation containing 0.75 mg.g-1 of basil essential oil presented antioxidant activity in relation to the lipids, but not to the proteins - during processing and storage.

The role of keratin intermediate filaments in the colon epithelial cells

Keratins (K) are cytoskeletal proteins mainly expressed in the epithelium and constitute the largest subgroup of intermediate filaments (IFs). Simple epithelial keratins (SEKs) K7-K8 and K18-K20 are the major IF elements in the colon. SEK mutations are known to cause around 30 human diseases, mainly affecting liver and skin. However, so far no strong associations between K8 mutations and the development of human colitis have been found. The keratin contribution to colonic health comes from the K8 knock-out (K8-/-) mouse model, which develops an early chronic inflammation and hyperproliferation in the colon. The aim of this thesis was to investigate how keratins contribute to intestinal health and disease mainly by the experimental analysis using the K8-/- mouse colon and cell culture models. The work described here is divided into three studies. The first study revealed involvement of keratins in Notch1 signaling, which is the master regulator of cell fate in the colon. Immunoprecipitation and immunostaining, both in vitro and in vivo showed that K8 binds and co-localizes with Notch1. Interestingly, overexpression of keratins enhanced Notch1 levels and stabilized Notch intracellular domain (NICD), leading to higher activity of Notch signaling. The dramatic decrease in Notch activity in the K8-/- colon resulted in a differentiation shift towards goblet and enteroendocrine cells. The second study focused on the involvement of keratins in colitis-associated cancer (CAC). Although, the K8-/- inflamed colon did not develop colorectal cancer (CRC) spontaneously, it was dramatically more susceptible to induced CRC in two CRC models: azoxymethane (AOM) and multiple intestinal neoplasia (ApcMin/+). To understand how the loss of K8 contributes to CAC, the epithelial inflammasome signaling pathway was analyzed. The released component of active inflammasome, cleaved caspase-1 and its downstream protein, interleukin (IL)-18, were significantly increased in K8-/- and K8-/-ApcMin/+ colons. The inflammasome pathway has recently been suggested to control the levels of IL-22 binding protein (IL-22BP), which is a negative regulator of IL-22 activity. Interestingly, the activated inflammasome correlated with an upregulation of IL-22 and a complete loss of IL-22BP in the K8-null colons. The activation of IL-22 was confirmed by increased levels of downstream signaling, which is phosphorylated signal transducer and activator of transcription 3 (P-STAT3), a transcription factor promoting proliferation and tissue regeneration in the colon. The objective of the third study, was to examine the role of keratins in colon energy metabolism. A proteomic analysis identified mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase 2 (HMGCS2) as the major ownregulated protein in the K8-/- colonocytes. HMGCS2 is the rate-limiting enzyme in ketogenesis, where energy from bacterially produced short chain fatty acids (SCFAs), mainly butyrate, is converted into ketone bodies in colonic epithelium. Lower levels and activity of HMGCS2 in the K8-/- colon resulted in a blunted ketogenesis. The studies upstream from HMGCS2, identified decreased levels of the SCFA-transporter monocarboxylate transporter 1 (MCT1), which led to increased SCFA content in the stool suggesting impaired butyrate transport through the colonic epithelium. Taken together, the results of the herein thesis indicate that keratins are essential regulators of colon homeostasis, in particular epithelial differentiation, tumorigenesis and energy metabolism.

Assessment of chromatin activity in mouse and human tissues

Pancreatic deoxyribonuclease preferentially digests active genes during all phases of the cell cycle including mitosis. Recently, a DNAse I-directed in ~ nick translation technique has been used to demonstrate differences in the DNAse I sensitivity of euchromatic and heterochromatic regions of mitotic chromosomes. This ill ~ technique has been used in this study to ask whether facultative heterochromatin of the inactive X chromosome can be distinguished from the active X chromosome in mouse and human tissues. In addition to this, in ~ nick translation has been used to distinguish constitutive heterochromatin in mouse and human mitotic chromosomes. Based on relative levels of DNAse I sensitivity, the inactive X chromosome could not be distinguished from the active X chromosome in either mouse or human tissues but regions of constitutive heterochromatin could be distinguished by their relative DNAse I insensitivity. The use of !D situ nick translation was also applied to tissue sections of 7.5 day mouse embryos to ask whether differing levels of DNAse I sensitivity could be detected between different tissue types. Differences in DNAse I sensitivities were detected in three tissues examined; embryonic ectoderm, an embryo-derived tissue, and two extraembryonic tissues, extraembryonic ectoderm and ectoplacental cone. Embryonic ectoderm and extraembryonic ectoderm nuclei possessed comparable levels of DNAse I sensitivity while ectoplacental cone was significantly less DNAse I sensitive. This suggests that tissue-specific mechanisms such as chromatin structure may be involved in the regulation of gene activity in certain tissue types. This may also shed some light on possible tissue specific mechanisms regulating X chromosome activity in the developing mouse embryo.

Thermoacclimatory variations in the activities of enzymes implicated in ion transport in the rainbow trout, salmo gairdneri

Two groups of rainbow trout were acclimated to 20 , 100 , and 18 o C. Plasma sodium, potassium, and chloride levels were determined for both. One group was employed in the estimation of branchial and renal (Na+-K+)-stimulated, (HC0 3-)-stimulated, and CMg++)-dependent ATPase activities, while the other was used in the measurement of carbonic anhydrase activity in the blood, gill and kidney. Assays were conducted using two incubation temperature schemes. One provided for incubation of all preparations at a common temperature of 2S oC, a value equivalent to the upper incipient lethal level for this species. In the other procedure the preparations were incubated at the appropriate acclimation temperature of the sampled fish. Trout were able to maintain plasma sodium and chloride levels essentially constant over the temperature range employed. The different incubation temperature protocols produced different levels of activity, and, in some cases, contrary trends with respect to acclimation temperature. This information was discussed in relation to previous work on gill and kidney. The standing-gradient flow hypothesis was discussed with reference to the structure of the chloride cell, known thermallyinduced changes in ion uptake, and the enzyme activities obtained in this study. Modifications of the model of gill lon uptake suggested by Maetz (1971) were proposed; high and low temperature models resulting. In short, ion transport at the gill at low temperatures appears to involve sodium and chloride 2 uptake by heteroionic exchange mechanisms working in association w.lth ca.rbonlc anhydrase. G.l ll ( Na + -K + ) -ATPase and erythrocyte carbonic anhydrase seem to provide the supplemental uptake required at higher temperatures. It appears that the kidney is prominent in ion transport at low temperatures while the gill is more important at high temperatures. 3 Linear regression analyses involving weight, plasma ion levels, and enzyme activities indicated several trends, the most significant being the interrelationship observed between plasma sodium and chloride. This, and other data obtained in the study was considered in light of the theory that a link exists between plasma sodium and chloride regulatory mechanisms.

Plasticity of neuroanatomical relationships between cholinergic and dopaminergic axon varicosities and pyramidal cells in the rat medial prefrontal cortex

Les systèmes cholinergique et dopaminergique jouent un rôle prépondérant dans les fonctions cognitives. Ce rôle est exercé principalement grâce à leur action modulatrice de l’activité des neurones pyramidaux du cortex préfrontal. L’interaction pharmacologique entre ces systèmes est bien documentée mais les études de leurs interactions neuroanatomiques sont rares, étant donné qu’ils sont impliqués dans une transmission diffuse plutôt que synaptique. Ce travail de thèse visait à développer une expertise pour analyser ce type de transmission diffuse en microscopie confocale. Nous avons étudié les relations de microproximité entre ces différents systèmes dans le cortex préfrontal médian (mPFC) de rats et souris. En particulier, la densité des varicosités axonales en passant a été quantifiée dans les segments des fibres cholinergiques et dopaminergiques à une distance mutuelle de moins de 3 µm ou à moins de 3 µm des somas de cellules pyramidales. Cette microproximité était considérée comme une zone d’interaction probable entre les éléments neuronaux. La quantification était effectuée après triple-marquage par immunofluorescence et acquisition des images de 1 µm par microscopie confocale. Afin d’étudier la plasticité de ces relations de microproximité, cette analyse a été effectuée dans des conditions témoins, après une activation du mPFC et dans un modèle de schizophrénie par déplétion des neurones cholinergiques du noyau accumbens. Les résultats démontrent que 1. Les fibres cholinergiques interagissent avec des fibres dopaminergiques et ce sur les mêmes neurones pyramidaux de la couche V du mPFC. Ce résultat suggère différents apports des systèmes cholinergique et dopaminergique dans l’intégration effectuée par une même cellule pyramidale. 2. La densité des varicosités en passant cholinergiques et dopaminergiques sur des segments de fibre en microproximité réciproque est plus élevée comparé aux segments plus distants les uns des autres. Ce résultat suggère un enrichissement du nombre de varicosités axonales dans les zones d’interaction. 3. La densité des varicosités en passant sur des segments de fibre cholinergique en microproximité de cellules pyramidales, immunoúactives pour c-Fos après une stimulation visuelle et une stimulation électrique des noyaux cholinergiques projetant au mPFC est plus élevée que la densité des varicosités de segments en microproximité de cellules pyramidales non-activées. Ce résultat suggère un enrichissement des varicosités axonales dépendant de l’activité neuronale locale au niveau de la zone d'interaction avec d'autres éléments neuronaux. 4. La densité des varicosités en passant des fibres dopaminergiques a été significativement diminuée dans le mPFC de rats ayant subi une déplétion cholinergique dans le noyau accumbens, comparée aux témoins. Ces résultats supportent des interrelations entre la plasticité structurelle des varicosités dopaminergiques et le fonctionnement cortical. L’ensemble des donneès démontre une plasticité de la densité locale des varicosités axonales en fonction de l’activité neuronale locale. Cet enrichissement activité-dépendant contribue vraisemblablement au maintien d’une interaction neurochimique entre deux éléments neuronaux.

Equatorial waves in the lower stratosphere. I: A novel detection method

Wavenumber-frequency spectral analysis and linear wave theory are combined in a novel method to quantitatively estimate equatorial wave activity in the tropical lower stratosphere. The method requires temperature and velocity observations that are regularly spaced in latitude, longitude and time; it is therefore applied to the ECMWF 15-year re-analysis dataset (ERA-15). Signals consistent with idealized Kelvin and Rossby-gravity waves are found at wavenumbers and frequencies in agreement with previous studies. When averaged over 1981-93, the Kelvin wave explains approximately 1 K-2 of temperature variance on the equator at 100 hPa, while the Rossby-gravity wave explains approximately 1 m(2)s(-2) of meridional wind variance. Some inertio-gravity wave and equatorial Rossby wave signals are also found; however the resolution of ERA-15 is not sufficient for the method to provide an accurate climatology of waves with high meridional structure.

Induction of cytochrome P-450 activity in individual Chironomus riparius Meigen larvae exposed to xenobiotics

Cytochrome P450 activity in individual Chironomus riparius larvae was measured using a microtiter plate adaptation of the ethoxyresorufin-O-deethylase (EROD) assay. The sensitivity of this biomarker was tested by exposing larvae to phenobarbital (0.5 and 1.0 mM) and permethrin (1 and 10 mug/g). Both chemicals induced EROD activity in C. riparius larvae by up to 1.58-fold with PB and 2.47-fold with permethrin. EROD induction was more pronounced after 48 h. The initially high EROD activity in the controls suggested that P450s are induced by stress. Feeding levels prior to exposure also had a significant effect on EROD activity. EROD activity compared to the control was highest when larvae were fed double the normal ration. These results indicate that EROD activity in individual C. riparius may be a useful biomarker to add to a suite of biomarkers for the detection of freshwater pollution. (C) 2002 Elsevier Science (USA). All rights reserved.