Efficacy of quorum sensing and growth inhibitors alone and in combination against avian pathogenic Escherichia coli infection in chickens.

Avian pathogenic E. coli (APEC), a causative agent of colibacillosis, is associated with high mortality and morbidity which results in severe economic losses to the poultry industry worldwide. APEC can be transmitted to humans through the consumption of contaminated poultry products. The limited effect of the current vaccines and the advent of drug-resistant strains have necessitated the development of alternative therapies. Previously, we identified 2 small molecules (SMs; [quorum sensing inhibitor; QSI-5] and [growth inhibitor; GI-7]) with high efficacy in vitro and in chickens subcutaneously challenged with APEC O78. Here, we optimized the oral challenge dose of APEC O78 in chickens to mimic the infection in the natural settings, evaluated the efficacy of the GI-7, QSI-5, and combination of GI-7 and QSI-5 (GI7+ QSI-5) in chickens orally infected with APEC, and compared their efficacy to sulfadimethoxine (SDM), an antibiotic currently used to treat APEC. Using the optimized dose of each SM in drinking water, GI-7, QSI-5, GI7+ QSI-5, and SDM were evaluated in chickens challenged with the optimized dose of APEC O78 (1 × 109 CFU/chicken; orally; d 2 of age) and grown on built-up floor litter. Reduction in mortality was 90, 80, 80, and 70% in QSI-5, GI-7+QSI-5, GI-7, and SDM treated groups compared to the positive control (PC), respectively. GI-7, QSI-5, GI-7+QSI-5, and SDM reduced the APEC load in the cecum by 2.2, 2.3, 1.6, and 0.6 logs and in the internal organs by 1.3, 1.2, 1.4, and 0.4 logs compared to PC (P < 0.05), respectively. The cumulative pathological lesions scores were 0.51, 0.24, 0.0, 0.53, and 1.53 in GI-7, QSI-5, GI-7+QSI-5, SDM, and PC groups, respectively. Overall, GI-7 and QSI-5 individually have promising effects as a potential antibiotic-independent approach to control APEC infections in chickens.

Evaluation of Novel Quorum Sensing Inhibitors Targeting Auto-Inducer 2 (AI-2) for the Control of Avian Pathogenic Escherichia coli Infections in Chickens.

Avian pathogenic Escherichia coli (APEC) associated with colibacillosis results in high morbidity and mortality, and severe economic losses to the poultry industry. APEC is a zoonotic pathogen and can infect humans through contaminated poultry products. Vaccination and antibiotic treatment are currently used to control APEC infections; however, the limited effect of vaccines and the emergence of antibiotic-resistant strains have necessitated the development of novel therapeutics. Here, we evaluated seven quorum sensing inhibitors (QSI) identified in our previous study, in APEC-infected chickens. QSIs were administered orally (~92 to 120 µg/bird) and chickens were challenged subcutaneously with APEC. Among them, QSI-5 conferred the best protection (100% reduction in mortality, 82% to 93% reduction in lesions [airsacculitis, perihepatitis, lung congestion, pericarditis] severity, and 5.2 to 6.1 logs reduction in APEC load). QSI-5 was further tested in chickens raised on built-up floor litter using an optimized dose (1 mg/L) in drinking water. QSI-5 reduced the mortality (88.4%), lesion severity (72.2%), and APEC load (2.8 logs) in chickens, which was better than the reduction observed with currently used antibiotic sulfadimethoxine (SDM; mortality 35.9%; lesion severity up to 36.9%; and APEC load up to 2.4 logs). QSI-5 was detected in chicken's blood after 0.5 h with no residues in muscle, liver, and kidney. QSI-5 increased the body weight gain with no effect on the feed conversion ratio and cecal microbiota of the chickens. Metabolomic studies revealed reduced levels of 5'-methylthioadenosine in QSI-5-treated chicken serum. In conclusion, QSI-5 displayed promising effects in chickens and thus, represents a novel anti-APEC therapeutic. IMPORTANCE Avian pathogenic Escherichia coli (APEC), a subgroup of ExPEC, is a zoonotic pathogen with public health importance. Quorum sensing is a mechanism that regulates virulence, biofilm formation, and pathogenesis in bacteria. Here, we identified a novel quorum sensing autoinducer-2 inhibitor, QSI-5, which showed higher anti-APEC efficacy in chickens compared to the currently used antibiotic, sulfadimethoxine at a much lower dose (up to 4,500 times). QSI-5 is readily absorbed with no residues in the tissues. QSI-5 also increased the chicken's body weight gain and did not impact the cecal microbiota composition. Overall, QSI-5 represents a promising lead compound for developing novel anti-virulence therapies with significant implications for treating APEC infections in chickens as well as other ExPEC associated infections in humans. Further identification of its target(s) and understanding the mechanism of action of QSI-5 in APEC will add to the future novel drug development efforts that can overcome the antimicrobial resistance problem.

Animals in Iodine Deficiency or Sulfadimethoxine Models of Thyroid Damage Are Differently Affected by the Consumption of Brassica Sprouts.

The study was primarily aimed at investigating the effect of brassica sprout consumption, namely rutabaga (Brassica napus L. var. napobrassica) sprouts (R) generally recognized as antithyroid agent due to its goitrogenic substance content, on hematological, biochemical, and immunological parameters in rats. Sprouts were tested alone and in a combination with other antithyroid factors, such as iodine deficiency (RDI) and sulfadimethoxine (RS). The expression of the heme oxygenase-1 (HO-1) gene in the thyroid as a stress-inducible protein was determined. The thermographic analysis was also estimated. The intake of rutabaga sprouts by healthy rats did not reveal any significant, harmful effect on the thyroid function. Both body temperature and expression of HO-1 remained unchanged in response to the consumed sprouts. In animals with hypothyroidism, rutabaga sprouts enhanced the negative effect of iodine deficiency or sulfadimethoxine ingestion on the organism by increasing the WBC (RDI), TNF-α (RS), creatinine (RS), and triglyceride (RDI and RS) levels, as well as decreasing PLT (RS) level. Moreover, rutabaga sprout consumption by rats with iodine deficiency and sulfadimethoxine decreased their body temperature. Additionally, the concomitant administration of sprouts and iodine depletion significantly reduced the expression of HO-1 in the thyroid. The results may prove useful in confirming rutabaga sprout consumption to be safe, though the seeds of this vegetable provide a well-known antithyroid agent. Our results have shown that rutabaga sprout consumption may be also a factor that enhances the negative clinical features only when combined with iodine deficiency and sulfadimethoxine ingestion.

Aberrant activation of M phase proteins by cell proliferation-evoking carcinogens after 28-day administration in rats.

We have previously reported that hepatocarcinogens increase liver cells expressing p21(Cip1), a G1 checkpoint protein and M phase proteins after 28-day treatment in rats. This study aimed to identify early prediction markers of carcinogens available in many target organs after 28-day treatment in rats. Immunohistochemical analysis was performed on Ki-67, p21(Cip1) and M phase proteins [nuclear Cdc2, phospho-Histone H3 (p-Histone H3), Aurora B and heterochromatin protein 1α (HP1α)] with carcinogens targeting different organs. Carcinogens targeting thyroid (sulfadimethoxine; SDM), urinary bladder (phenylethyl isothiocyanate), forestomach (butylated hydroxyanisole; BHA), glandular stomach (catechol; CC), and colon (2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine and chenodeoxycholic acid) were examined using a non-carcinogenic toxicant (caprolactam) and carcinogens targeting other organs as negative controls. All carcinogens increased Ki-67(+), nuclear Cdc2(+), p-Histone H3(+) or Aurora B(+) carcinogenic target cells, except for both colon carcinogens, which did not increase cell proliferation. On the other hand, p21(Cip1+) cells increased with SDM and CC. HP1α responded only to BHA. Results revealed carcinogens evoking cell proliferation concurrently induced cell cycle arrest at M phase or showing chromosomal instability reflecting aberration in cell cycle regulation, irrespective of target organs, after 28-day treatment. Therefore, M phase proteins may be early prediction markers of carcinogens evoking cell proliferation in many target organs.

Characteristics of Staphylococcus aureus small colony variant and its parent strain isolated from chronic mastitis at a dairy farm in Beijing, China.

Staphylococcus aureus is a major pathogen associated to bovine mastitis and has the ability to form a slow-growing population termed the small colony variants (SCVs). From 20 samples of 5 chronic S. aureus cases, 1 SCV isolate (SCV102) was recovered simultaneously with 1 of 8 S. aureus isolates. SCV102 showed auxotrophy for thymidine and had a slow growth rate. Intracellular persistence in human mammary epithelial cells (HBL100cell line) monolayer revealed that SCV102 isolate had minimal cytopathological effects compared with its parent strains. SCV102 isolate and its parent strain S. aureus 101 indicate similar resistant pattern to four antibiotics. On the contrary, the minimal inhibitory concentrations values for chloramphenicol and sulfadimethoxine were much higher in SCV102 than that of S. aureus 101. To the best of our knowledge this is the first time the isolation of S. aureus SCV102 from a persistent bovine mastitis has been reported in Beijing (China). This study suggests that SCV102 isolate may be an important contributor to persistent bovine mastitis.

Prostaglandin synthases influence thyroid follicular cell proliferation but not carcinogenesis in rats initiated with N-bis(2-hydroxypropyl)nitrosamine.

To clarify roles of prostaglandin synthases in rat thyroid follicular carcinogenesis, effects of an antithyroid agent, sulfadimethoxine (SDM), and two prostaglandin H synthase (COX) inhibitors, indomethacin and nimesulide, on prostaglandin synthase expression, follicular cell proliferation, and tumor induction in thyroids of rats with or without N-bis(2-hydroxypropyl)nitrosamine (DHPN) initiation were examined. In experiment 1, F344 male rats were allowed free access to drinking water containing SDM (0.1%), SDM + indomethacin (0.0025% in diet), or SDM + nimesulide (0.04% in diet) for 4 weeks. Both COX inhibitors suppressed goitrogenic activity of SDM, but they did not significantly affect microsomal prostaglandin E synthase-2 (mPGES-2) expression levels enhanced by SDM. In experiment 2, all rats received an injection of DHPN (2800 mg/kg body weight), and starting 1 week later, they were treated as in experiment 1 for 4 or 10 weeks. Cell proliferation was suppressed or showed a tendency for suppression by the COX inhibitors in the follicular preneoplastic/neoplastic lesions and surrounding parenchyma, and this was obviously thyroid stimulating hormone independent at least at week 4. However, neither of the COX inhibitors altered the incidence or multiplicity of preneoplastic/neoplastic lesions. Immunohistochemistry revealed significant reduction and elevation of COX-2 and mPGES-2 expression, respectively, in the lesions, but these were also not changed by the COX inhibitors. These results suggest that COX-2 and PGES, and in turn PGE(2), might play important roles in follicular cell proliferation but do not affect tumor induction in this rat thyroid carcinogenesis model. Further studies are needed to clarify the significance of the reduction of COX-2 expression in preneoplastic/neoplastic lesions.

Bilirubin accumulation and Cyp mRNA expression in selected brain regions of jaundiced Gunn rat pups.

INTRODUCTION: Few data exist on regional brain bilirubin content in the neonatal period when acute bilirubin-induced neurologic damage (BIND) may occur, and no information is available on regional brain expression of cytochrome P450 monooxygenases (Cyps) that oxidize bilirubin. METHODS: Bilirubin content was analyzed by high-performance liquid chromatography and Cyp1a1, 1a2, and 2a3 mRNA expression was analyzed by quantitative PCR (qPCR) in cortex (Cx), cerebellum (Cll), superior colliculi (SC), and inferior colliculi (IC) of 17-d-old hyperbilirubinemic (jj) Gunn rat pups before and after administration of sulphadimethoxine to acutely displace bilirubin from plasma albumin. RESULTS: There was no difference in bilirubin content among brain regions in untreated rats. After intraperitoneal sulphadimethoxine, bilirubin content peaked at fourfold in Cx and SC at 1 h; but at 11- to 13-fold in Cll and IC at 24 h; returning to control levels at 72 h. The Cyp mRNA peaked at 30-70 times control at 1 h in Cx and SC, but at 3-9 times control at 24 h in Cll and IC. DISCUSSION: The close relationship in distinct brain regions between the extent of bilirubin accumulation and induction of mRNA of Cyps suggests Cyps may have a role in protecting selected brain areas from bilirubin neurotoxicity.

Antimicrobial resistance in fecal Escherichia coli isolated from growing chickens on commercial broiler farms.

To investigate the effects of rearing practices of commercial broiler chickens on the incidence of antimicrobial resistance in commensal Escherichia coli isolates, fecal E. coli isolates obtained in 4 farms were screened for anitimicrobial resistance. Ten E. coli isolates were recovered from each of the fecal samples collected from 10 birds in the farms at the ages of 2 days, 14-17 days, and 47-50 days. In 2 out of the 4 farms, no antimicrobials were used during the rearing period. In the other two farms, following collection of the fecal samples at 14 and 15 days of age, oxytetracycline (OTC), sulfadimethoxine (SDMX), and tylosin were given to birds on one farm and SDMX was used in the other. Isolates resistant to ampicillin and OTC that were obtained from an untreated flock at different sampling times were closely related to each other by pulsed-field gel electrophoresis patterns (PFGE) of XbaI-digested chromosomal DNA. PFGE analysis together with in vitro conjugation experiments suggested that diversity of resistance phenotypes within a clone may be resulted from the acquisition and loss of R-plasmids in an untreated and a treated flock. The numbers of resistance phenotypes observed among fecal isolates increased during the growth of the chickens in all the farms. The results in the present study suggest that persistence of commensal E. coli strains resistant to antimicrobials even in the absence of antimicrobial administration. It is also hypothesized that horizontal transmission of resistance determinants resulted in the emergence of different resistance phenotypes in those farms.

[Combined effect of antibiotics on anaerobic digestion of piggery wastewater].

In order to investigate the combined effects of antibiotics on anaerobic digestion of piggery wastewater, batch tests based on orthogonal test were adopted. Amoxicillin, aureomycin, sulfadimethoxine, florfenicol which are the most common antibiotics used in the prevention and treatment of pig diseases were chosen in the experiment. The results showed that the methane production rate was affected most by the combination of 130 mg/L of florfenicol, 210 mg/L of amoxicillin, 10 mg/L doxycycline and 210 mg/L sulfadimethoxine and the inhibitory effect on maximum methane production rate amounted to 87.8%. No inhibitory effect but stimulus was observed on anaerobic digestion in the presence of florfenicol, amoxicillin, aureomycin, sulfadimethoxine with 10 mg/L. The significance of the inhibitory effect of the selected antibiotics was in an order of aureomycin, amoxicillin, florfenicol and sulfadimethoxine (p > 0.005). Different kinds of first-order interactions between either two antibiotics were concluded from the experiment. Except that florfenicol was in a additivity relationship with amoxicillin and sulfadimethoxine the interaction in other antibitotics was antagonistic.

Atoxoplasmosis in canary fledglings: severe lymphocytic enteritis with preferential parasitism of B lymphocytes.

All fledgling canaries (Serinum canarius) in a small private aviary died from atoxoplasmosis during a single breeding season. The birds were clinically normal when removed from their parents at 2 mo of age, but by 3 mo of age all had died following an illness characterized by progressive lethargy, anorexia, and debilitation. Cachexia, splenomegaly, and pale foci in the liver were evident at necropsy. Microscopically, there was striking infiltration of the intestinal lamina propria by mononuclear cells that contained intracytoplasmic protozoa. Protozoa were also observed in mononuclear cells in splenic and hepatic sinusoids and in vascular or perivascular spaces of other organs, but were much less numerous. Ultrastructural features of infected enteric mononuclear cells were suggestive of lymphocytes, and the majority of parasitized cells in paraffin sections of intestine were positive for CD-79 antigen, consistent with B lymphocytes. CD-3 staining was minimal, suggesting little or no T-cell infection. The following year, after egg-laying was completed, adults were treated with sulfadimethoxine, and no further fledgling losses occurred.

[Effects of antimicrobial drugs on soil microbial respiration].

The effects on soil microbial respiration of sulfonamides, tetracyclines, macrolides and so on were studied using the direct absorption method. The results show sulfamethazine, sulfamethoxazole, chlortetracycline, tetracycline, tylosin and trimethoprim inhibit soil respiration 34.33%, 34.43%, 2.71%, 3.08%, 7.13%, 38.08% respectively. Sulfamethoxazole and trimethoprim have the highest inhibition rates among all the antibiotics. In early incubation period (0-2 d), the concentrations above 10 mg x kg(-1) of sulfamethazine, sulfamethoxazole and trimethoprim remarkably decrease soil CO2 emission. The effects of these antibiotics vary with their concentrations too. Sulfamethoxazole and trimethoprim show good dose-response relationships. According to the standard of pesticide safety evaluation protocol, the six antibiotics pose a little risk to soil microbial environment.

Sulphadimethoxine inhibits Phaseolus vulgaris root growth and development of N-fixing nodules.

Sulphonamides contamination of cultivated lands occurs through the recurrent spreading of animal wastes from intensive farming. The aim of this study was to test the effect(s) of sulphadimethoxine on the beneficial N-fixing Rhizobium etli-Phaseolus vulgaris symbiosis under laboratory conditions. The consequence of increasing concentrations of sulphadimethoxine on the growth ability of free-living R. etli bacteria, as well as on seed germination, seedling development and growth of common bean plants was examined. We have established that sulphadimethoxine inhibited the growth of both symbiotic partners in a dose-dependent manner. Bacterial invasion occurring in developing root nodules was visualized by fluorescence microscopy generating EGFP-marked R. etli bacteria. Our results proved that the development of symbiotic N-fixing root nodules is hampered by sulphadimethoxine thus identifying sulphonamides as toxic compounds for the Rhizobium-legume symbiosis: a low-input sustainable agricultural practice.

A multifactorial test of the effects of carotenoid access, food intake and parasite load on the production of ornamental feathers and bill coloration in American goldfinches.

It has been well established that carotenoid and melanin pigmentation are often condition-dependent traits in vertebrates. Expression of carotenoid coloration in birds has been shown to reflect pigment intake, food access and parasite load; however, the relative importance of and the potential interactions among these factors have not been previously considered. Moreover, carotenoid and melanin pigmentation have been proposed to signal fundamentally different aspects of individual condition but few data exist to test this idea. We simultaneously manipulated three environmental conditions under which American goldfinches (Cardeulis tristis) grew colorful feathers and developed carotenoid pigmentation of their bills. Male goldfinches were held with either high or low carotenoid supplementation, pulsed or continuous antimicrobial drug treatment, or restricted or unlimited access to food. Carotenoid supplementation had an overriding effect on yellow feather coloration. Males given more lutein and zeaxanthin grew yellow feathers with hue shifted toward orange and with higher yellow chroma than males supplemented with fewer carotenoids. Parasites and food access did not significantly affect yellow feather coloration, and there were only minor interaction effects for the three treatments. By contrast, bill coloration was significantly affected by all three treatments. Carotenoid supplementation had a significant effect on yellow chroma of bills, drug treatment and food access both had a significant effect on bill hue, and food access had a significant effect on the yellow brightness of bills. Neither the size nor blackness of the black caps of male goldfinches was affected by any treatment. These results indicate that pigment intake, food access and parasite load can have complex and variable effects on color displays, and that feather and bill coloration signal different aspects of male condition.

Role of a novel multifunctional excipient poly(ethylene glycol)-block-oligo(vinyl sulfadimethoxine) in controlled release of lysozyme from PLGA microspheres.

This study investigated the effect of ion-pairing of anionic polyelectrolytes: our novel poly(ethylene glycol)-block-oligo(vinyl sulfadimethoxine) (PEG-OVSDM) and poly(ethylene glycol)-block-poly(l-aspartic acid) (PEG-PAA) with cationic lysozyme on retention of protein stability during emulsification. Soluble lysozyme recovery after exposure to the deleterious interface was 42-88% (when ion-paired with PEG-OVSDM, PEG-OVSDM concentration dependent) compared to only 30% for free lysozyme. PEG-OVSDM provided a higher stabilization of lysozyme than PEG-PAA (36-60%). Lysozyme when recovered in the aqueous phase and analyzed by chromatography, enzymatic assay, fluorescence, and mass spectrometry showed no significant physicochemical change when compared with a lysozyme standard. Lysozyme was incorporated into poly(lactide-co-glycolide) (PLGA) microspheres via the typical double emulsion method. Incorporation of lysozyme complexes led to a higher encapsulation efficiency and loading amount, and a lower incidence of insoluble lysozyme aggregates compared to the control microspheres containing lysozyme only. More significantly, ion-pairing was able to dramatically reduce the initial lysozyme release to 18% compared with 50% from control microspheres and provided an overall better control of protein release. PEG-PAA was less effective than PEG-OVSDM in controlling the release probably due to weaker interactions between this polyelectrolyte and lysozyme. Manipulation of such polyelectrolyte-protein complexation may play a role in protein-controlled delivery.

Observational study of hepatic cytochrome P-450 protein expression and activity in summer flounder (Paralichtys dentatus) after combination ormetoprim-sulfadimethoxine treatment.

The metabolism of aquaculture antibiotics on the piscine, hepatic cytochrome P-450 (CYP) system has not yet been defined. Fifty summer flounder, maintained at 20 degrees C, were fed ormetoprim-sulfadimethoxine (Romet-30(R)) at 1% body weight daily and were randomly sampled before treatment and on days 1, 6, 10 and 21 after treatment. Western blotting of hepatic microsomes included goat antirat CYP1A1 and rabbit antihuman CYP3A4 serum. Catalytic activities comprised: 3-cyano-7-ethoxycoumarin (CEC), 7-benzyloxy-4-trifluoromethylcoumarin (BFC), resorufin benzyl ether (BzRes). Treatment induced CYP1A1 and CYP3A4 expression. Dealkylation of CEC (CYP1A2) was increased after treatment. Romet-30 inhibited CYP3A4 activity measured by BFC, but induced BzRes CYP3A4. The usefulness of mammalian antibodies for piscine P-450 Western blotting was demonstrated. The hepatic P-450 1A2 and 3A4 metabolism was quantifiable by kits developed for mammalian microsomes.

Calculated in vivo free bilirubin levels in the central nervous system of Gunn rat pups.

In vitro studies suggest a free bilirubin (B(F)) concentration in the range of 71-770 nmol/L can induce neurotoxicity. In vivo data regarding central nervous system (CNS) B(F) levels have not been determined. We calculated in vivo CNS B(F) levels in Gunn rat pups (15-19 d old; heterozygous nonjaundiced Gunn rats (J/j) and homozygous jaundiced Gunn rats (j/j); saline or sulfadimethoxine treated) based on 1) total brain bilirubin (TBB) content, 2) brain albumin level, 3) CNS bilirubin binding capacity attributable to brain albumin determined using an ultrafiltration technique, and 4) published Gunn rat albumin-bilirubin binding constants (k). Gunn rat brain bilirubin binding capacity was approximately 22 x 10(-3) micromol/g, of which two thirds was accounted for by brain albumin. Using a Gunn rat pup in vivo, k of 9.2 L/micromol, calculated CNS B(F) levels ranged from 72 to 112 nmol/L [95% confidence interval (CI)] in saline and from 59 to 156 nmol/L (95% CI) in sulfadimethoxine-treated J/j pups. These animals demonstrated no neurobehavioral abnormalities and normal cerebellar weight. Calculated CNS B(F) levels were severalfold higher (p < 0.001) in saline (95% CI: 556-1110 nmol/L) and sulfadimethoxine-treated (95% CI: 3461-8985 nmol/L) j/j pups; the former evidenced reduced cerebellar weight; the latter both reduced cerebellar weight and acute neurobehavioral abnormalities. We conclude that calculated CNS B(F) values in j/j pups are substantially higher than those in J/j animals. Given the absence of CNS abnormalities in J/j pups, the presence of such in j/j animals, and the CNS B(F) levels in these groups, we speculate that the CNS B(F) neurotoxicity threshold in vivo is subsumed within the range (71-770 nmol/L) reported in vitro.

Effect of selective cyclooxygenase-2 inhibitors on heart rate in healthy young men.

During an investigation of the possible pharmacokinetic interactions of cyclooxygenase-2 (COX-2) inhibitors with metoprolol, we observed that rofecoxib caused a significant reduction in heart rate in young healthy volunteers. The effect of valdecoxib did not reach significance. When these drugs were given together with metoprolol, the effect was continued. The latter effect could not be related to pharmacokinetic interactions. In the light of experimental results claiming a cardioprotective effect of possibly COX-2-derived prostaglandins and clinical observations hinting at an increased risk of sudden cardiovascular death in conjunction with the long-term use of selective cyclooxygenase inhibitors, our results may help to increase awareness and to suggest investigation of the impact of coxibs on heart function.

Development of invasive follicular cell carcinomas in a rat thyroid carcinogenesis model: biological impact of capsular inflammation and reduced cyclooxygenase-2 expression.

We have previously reported that thyroid capsular inflammation induced by sulfadimethoxine (SDM), a goitrogen, might play a role in development of invasive follicular cell adenocarcinomas in rats initiated with N-bis(2-hydroxypropyl)nitrosamine (DHPN). The present study was designed to examine the role of cyclooxygenase (COX)-2, widely known to be up-regulated in inflammatory states, during chemically induced rat thyroid carcinogenesis. Male F344 rats received a subcutaneous DHPN (2800 mg/kg) injection, and 1 week later were allowed free access to drinking water containing antithyroidal propylthiouracil (PTU, 0.003%) or SDM (0.1%) for 4 or 10 weeks. Control groups receiving goitrogen alone and no treatment were also included. At week 4, diffuse follicular cell hyperplasia was induced in all PTU- and SDM-treated groups, along with fibrous capsular thickening and capsular thickening with inflammation, respectively. Additionally, multiple focal follicular cell hyperplasias and adenomas were observed in the DHPN + PTU and DHPN + SDM cases. At week 10, adenocarcinomas invasive to the capsule and restricted to the capsular adjacent region, were frequent in the DHPN + SDM group, but not observed in the animals given DHPN + PTU. Western blots and immunohistochemistry revealed constitutive COX-2 expression in non-neoplastic follicular cells of the control and all of the PTU- and SDM-treated rats. However, COX-2 reactivity was significantly reduced or negative in the preneoplastic/neoplastic lesions in the DHPN-treated groups. In fibrous or inflamed thickened capsules, only a few component cells with inflammatory elements were positive for COX-2, and there was no significant difference in this regard between the PTU and SDM treatments. The present results suggest that capsular inflammation could play a role in development of invasive carcinomas, but COX-2 expression does not make a major contribution.

Pharmacokinetics of sulfadimethoxine and ormetoprim in a 5:1 ratio following intraperitoneal and oral administration, in the hybrid striped bass (Morone chrysops x Morone saxitalis).

Selected pharmacokinetic parameters for sulfadimethoxine and ormetoprim, administered in a 5:1 ratio, via the oral and intraperitoneal (i.p.) routes were determined in the hybrid striped bass (Morone chrysops x Morone saxitalis). Plasma concentrations of both drugs were determined by high-performance liquid chromatography. A first-order one-compartment model adequately described plasma drug disposition. The elimination half-lives for sulfadimethoxine following i.p. and oral administration were 26 and 10.5 h, respectively. The half-lives for ormetoprim administered via i.p. and oral routes were 7.5 and 3.9 h, respectively. Cmax for sulfadimethoxine via the i.p. and oral routes were calculated to be 27.7 (+/-9.0) microg/mL at 3.6 h and 3.2 (+/-1.2) microg/mL at 1.2 h, respectively. Cmax for ormetoprim via the i.p. route was calculated to be 1.2 (+/-0.5) microg/mL at 9.1 h and 1.58 (+/-0.7) microg/mL at 5.7 h for the oral route. The oral availability of sulfadimethoxine relative to the i.p. route was 4.6%, while the oral availability of ormetoprim relative to the i.p. route was 78.5%. Due to the nonconstant ratio of these drugs in the plasma of the animal, the actual drug ratio to use for determining minimum inhibitory concentration (MIC) is unclear. Using the ratio of the total amount of each drug that is absorbed as a surrogate for the mean actual ratio may be the best alternative to current methods. Using this ratio as determined in these studies, (2.14:1 sulfadimethoxine:ormetoprim) to determine the MICs the single 50 mg/kg oral dose of the 5:1 combination of sulfadimethoxine and ormetoprim appears to provide plasma concentrations high enough to inhibit the growth of Yersinia ruckeri, Edwardsiella tarda, and Escherichia coli.

Efficacy of oral sulfadimethoxine against two gregarine parasites, Protomagalhaensia granulosae and Gregarina cubensis (Apicomplexa: Eugregarinida), infecting the Death's Head cockroach, Blaberus discoidalis.

Gregarines are common parasites of insects in culture, but no effective chemotherapeutic or prophylactic control protocol has been demonstrated. Sulfadimethoxine was administered in 5- and 7-day treatments to Death's Head cockroaches (Blaberus discoidalis) infected with Gregarina cubensis and Protomagalhaensia granulosae to test the efficacy of this sulfonamide against gregarine infection. Sulfadimethoxine significantly reduced the mean intensity of both G. cubensis and P. granulosae. Sulfadimethoxine treatment reduced gregarine intensity by 80% to 85% but had no significant effect on gametocyst production, suggesting that sulfonamide toxicity is directed primarily at sporozoites, trophozoites, and perhaps young gamonts. The possible use of sulfadimethoxine to produce gregarine-free insect cultures and the potential utility of gregarines as target organisms for screening pharmacologically active compounds for use against other intestinal apicomplexans are discussed.