Evaluation of the diphenyl herbicide, oxyfluorfen, for effects on thyroid hormones in the juvenile rat.

Recently, oxyfluorfen, a pre- and post-emergent diphenyl ether herbicide, was identified in our laboratory as an inhibitor of iodide uptake by the sodium iodide symporter (NIS), the first key step in the synthesis of thyroid hormones (THs). This inhibition was observed in vitro, using both a human NIS engineered cell line (hNIS-HEK293T-EPA) and a rat thyroid follicular cell line (FRTL-5). Oxyfluorfen was found to be a potent inhibitor of NIS activity with an EC50 of approximately 2 µM in both cell lines with no observed cytotoxicity at any concentration tested up to 100 µM. The current research tested the hypothesis that oxyfluorfen alters circulating concentrations of THs. This hypothesis was first tested in a pilot study with both juvenile male and female rats exposed to oxyfluorfen for 4 days at 0, 125, 250 and 500 mg/kg/day. Once we identified that this short-term 4-day oxyfluorfen exposure suppressed both total serum thyroxine (T4) and triiodothyronine (T3) at all doses, we tested seven lower concentrations of oxyfluorfen (0.8125 to 62.5 mg/kg day) in an 8-day exposure paradigm to more closely evaluate the dose-response. We found that oxyfluorfen suppressed serum T4 with a LOEL of 3.25 mg/kg/day and T3 with a LOEL 62.5 mg/kg/day. Analytical chemistry of the serum showed an accumulation over time following oral exposure to oxyfluorfen in both the 4- and 8-day groups. Analytical chemistry of the thyroid glands in the 8-day study revealed higher accumulation in the thyroid as compared to the serum (2 to 3- fold at 62.5 mg/kg). No changes in thyroid weight or serum TSH were observed following the 8-day exposure. This study is the first to demonstrate an effect of oxyfluorfen on serum thyroid hormones in the rat. Additional studies are needed to further evaluate the effects on thyroid homeostasis with extended exposures and the potential implications of the observed effects.

Laryngectomy with a Tritube® and flow-controlled ventilation.

We describe the novel use of the TriTube® and Evone® ventilator (Ventinova, Eindhoven, Netherlands) to facilitate curative resection of a transglottic squamous cell carcinoma. A 43-year-old man presented with acute laryngeal and subglottic airway obstruction secondary to a stage 4 transglottic squamous cell carcinoma. The patient underwent magnetic resonance imaging followed by a diagnostic panendoscopy. It was decided that tumour resection was appropriate and a management plan was established by a multi disciplinary team. A total laryngectomy was performed. It was determined that failure of translaryngeal tracheal intubation could be rescued with emergency surgical front-of-neck airway. General anaesthesia was induced using a total intravenous anaesthesia technique, oxygenation was achieved with high-flow nasal oxygen and the airway was secured using the TriTube and flow-controlled ventilation was delivered throughout the procedure using the Evone ventilator. This avoided an awake or emergency tracheostomy, with the associated theoretical risk of tumour seeding, allowed for excellent gas exchange throughout and permitted the surgeons to maintain a closed system during much of the procedure, including during fashioning of the stoma. When traditional laryngectomy tubes are used, this process ordinarily involves multiple extubations and apnoeic periods. Furthermore, the small subglottic tube allowed intra-operative assessment of the extent of the subglottic tumour, facilitating curative en bloc resection.

An investigation into most effective method of treating stained teeth: an in vitro study.

OBJECTIVE: To assess the most efficacious method of treating stained teeth: bleaching alone, veneering alone or a combination of bleaching and veneering and whether the choice alters depending on the degree of staining. METHODS: Extracted teeth were sectioned to give 117 samples. These samples were split into unstained, lightly and darkly stained groups based on CIE-Lab value L*. The lightly and darkly stained groups were stained using tea. Teeth from each group were then assigned to one of four subgroups (control (C), bleaching alone (B), veneering alone (V), or a combination of bleaching and veneering (BV), each containing 13 samples. Veneering was performed using 0.8-mm thick ceramic veneer of shade B1. CIE-Lab values were recorded using a spectrophotometer and the colour difference (Delta E) was calculated for each intervention. The final colour was compared to the value for obtained from a B1 (Vita) Shade tab. Statistical significance was assessed using analysis of variance. RESULTS: In all three test groups, intervention resulted in a statistically significant colour change compared to the C group (p

Oncogenic Vav1 induces Rac-dependent apoptosis via inhibition of Bcl-2 family proteins and collaborates with p53 deficiency to promote hematopoietic progenitor cell proliferation.

Vav1 is an hematopoietic-specific Rho guanine nucleotide exchange factor coupling tyrosine kinase receptors and Rac GTPases, and has been implicated in transformation of fibroblasts and pancreas. To determine the biologic effect and oncogenic potential of Vav1 in hematopoietic lineages, we stably express oncogenic mutant of Vav1 in primary bone marrow cells using retrovirus-mediated gene transfer. Contrary to the growth stimulatory effects observed in fibroblasts, oncogenic Vav1 inhibits hematopoietic stem cell/progenitor engraftment in vivo and progenitor cell expansion in vitro via inducing apoptosis. The oncogenic Vav1-induced apoptosis is associated with reduced expression of Bcl-2 and Bcl-xL proteins and effectively suppressed by transgenic overexpression of Bcl-2, suggesting Vav1-mediated signaling via Bcl-2 in apoptosis. Also, oncogenic Vav1 stimulates sustained activation of Rac GTPases and the biologic effects of oncogenic Vav1 are Rac-dependent. Further, when expressed in the p53-deficient cells, which express elevated Bcl-2 and Bcl-xL and are resistant to the apoptosis, oncogenic Vav1 enhances both proliferation and self-renewal of hematopoietic progenitor cells. These results demonstrate clear phenotypic differences between wild-type and p53(-/-) hematopoietic cells expressing oncogenic Vav1, and suggest oncogenic potential of Vav1-mediated pathways in primary hematopoietic cell when they collaborate with additional genetic hits that affect the p53 pathway.

Streptococcus thermophilus NCIMB 41856 ameliorates signs of colitis in an animal model of inflammatory bowel disease.

Treatment of inflammatory bowel disease (IBD) is mainly based on suppression of symptoms, often with numerous side effects. Trials of probiotics in IBD have frequently produced disappointing results. The majority of probiotics are unusual, since they do not require iron for growth, unlike many bacteria resident in the intestine. The IBD intestine is iron-rich due to bleeding and use of oral iron supplements; conventional probiotics would be rapidly outcompeted. We have evaluated an iron-responsive Streptococcus thermophilus strain for its potential to reduce signs of colitis. Efficacy of S. thermophilus was evaluated in the dextran sodium sulphate mouse model of colitis. Treated animals were given 1×108 cfu S. thermophilus per day and clinical observations were taken daily. At termination, gross and histopathological signs of disease, cellular infiltration, location of bacteria, and cytokine expression in the intestine were determined. S. thermophilus delayed onset of colitis and reduced clinical signs of disease, including bodyweight loss and gastrointestinal bleeding. It reduced bacterial translocation into the colonic tissue. Increased numbers of CD8+ intraepithelial lymphocytes were seen in control animals treated with S. thermophilus. S. thermophilus had no effect on gross pathology, histopathology or cytokine production in either colitic or control animals. We propose that S. thermophilus promotes maintenance of mucosal barrier function which reduces bacterial translocation, thereby reducing immune stimulation and associated inflammation. This allows mucosal healing, reducing gastrointestinal bleeding and weight loss. This could be studied as a locally-acting adjunct or alternative to current IBD treatments.

Frequency of urination and its effects on metabolism, pharmacokinetics, blood hemoglobin adduct formation, and liver and urinary bladder DNA adduct levels in beagle dogs given the carcinogen 4-aminobiphenyl.

The human urinary bladder carcinogen, 4-aminobiphenyl (ABP), is known to undergo hepatic metabolism to an N-hydroxy arylamine and its corresponding N-glucuronide. It has been proposed that these metabolites are both transported through the blood via renal filtration to the urinary bladder lumen where acidic pH can facilitate the hydrolysis of the N-glucuronide and enhance the conversion of N-hydroxy-4-aminobiphenyl (N-OH-ABP) to a reactive electrophile that will form covalent adducts with urothelial DNA. Blood ABP-hemoglobin adducts, which have been used to monitor human exposure to ABP, are believed to be formed by reactions within the erythrocyte involving N-OH-ABP that has entered the circulation from the liver or from reabsorption across the urothelium. To test these hypotheses directly, experimental data were obtained from female beagles given [3H]ABP (p.o., i.v., or intraurethrally). [3H]N-OH-ABP (i.v. or intraurethrally), or [3H]N-OH-ABP N-glucuronide (i.v.). Analyses included determinations of total ABP in whole blood and plasma, ABP-hemoglobin adducts in blood erythrocytes, ABP and N-OH-ABP levels (free and N-glucuronide) in urine, urine pH, frequency of urination (controlled by urethral catheter), rates of reabsorption of ABP and N-OH-ABP across the urothelium, and apparent volumes of distribution in the blood/tissue compartment. The major ABP-DNA adduct, N-(guan-8-yl)-4-aminobiphenyl, was also measured in urothelial and liver DNA using a sensitive immunochemical method. An analog/digital hybrid computer was then utilized to construct a multicompartmental pharmacokinetic model for ABP and its metabolites that separates: (a) absorption; (b) hepatic metabolism and distribution in blood and tissues; (c) ABP-hemoglobin adduct formation; (d) hydrolysis and reabsorption in the urinary bladder lumen; and (e) excretion. Using this model, cumulative exposure of the urothelium to free N-OH-ABP was simulated from the experimental data and used to predict ABP-DNA adduct formation in the urothelium. The results indicated that exposure to N-OH-ABP and subsequent ABP-DNA adduct formation are directly dependent on voiding frequency and to a lesser extent on urine pH. This was primarily due to the finding that, after p.o. dosing of ABP to dogs, the major portion of the total N-OH-ABP entering the bladder lumen was free N-OH-ABP (0.7% of the dose), with much lower amounts as the acid-labile N-glucuronide (0.3% of the dose).(ABSTRACT TRUNCATED AT 400 WORDS)

Transplacental pharmacokinetics and metabolism of diethylstilbestrol and 17 beta-estradiol in the pregnant rhesus monkey.

Experiments were performed to describe and compare the transplacental pharmacokinetics of the teratogen and transplacental carcinogen, diethylstilbestrol [4,4'-dihydroxy-alpha,alpha'-diethyl-trans, cis-stilbene (DES)], and the endogenous estrogen, 17 beta-estradiol (E2). Timed mated pregnant rhesus monkeys (119-137 days gestation) were anesthetized, and catheters were implanted in the maternal femoral artery and the interplacental fetal artery and vein using an extraamniotic technique. Single doses of either radiolabeled DES or E2 were administered via the maternal radial vein. Maternal plasma levels of labeled compound decreased rapidly after dose administration. Fetal plasma levels of radioactivity derived from either DES or E2 increased rapidly and then plateaued higher than maternal levels 1--2 h after dose administration. High pressure liquid chromatography of maternal and fetal plasma samples revealed both parent and conjugated metabolites of DES and E2. The principal metabolite of DES (DES monglucuronide) was radiolabeled and given to either the mother or the fetus iv. There was no significant cross-over of this metabolite in either direction. It is concluded that DES crosses the primate placenta in an unconjugated form and that, based on total radioactivity, placental transfer is similar to that of E2. The extensive fetoplacental metabolism of DES appears to be responsible for the greater half-life of this agent and its metabolites in the fetal circulation compared with the maternal circulation.

Apolipoprotein oxidation in the absence of lipid peroxidation enhances LDL uptake by macrophages.

A characteristic of the antioxidant, probucol, is its inability to inhibit apolipoprotein B fragmentation in low density lipoprotein (LDL), despite a pronounced ability to inhibit lipid oxidation on relatively lengthy exposure to Cu(II). Here we show that a short exposure of LDL to hydrogen peroxide and Cu(II) leads to 125I-labelled apolipoprotein B fragmentation, the production of malondialdehyde and hydroperoxides and leads to increased uptake by macrophages on subsequent culture. However, pre-loading LDL with probucol protects LDL from lipid oxidation but not protein fragmentation or macrophage uptake. The use of probucol to conduct studies on apolipoprotein B oxidation without extensive lipid oxidation may prove useful when studying LDL apolipoprotein damage on exposure to an aqueous free radical insult.

Transplacental passage of a human relaxin administered to rhesus monkeys.

A synthetic version of the human relaxin encoded by the human gene 2 (hR1x-2) was administered to pregnant rhesus monkeys (Macaca mulatta) on gestational days 141-158. Monkeys (three per group) received doses of 100 micrograms/kg or 2000 micrograms/kg as a continuous i.v. infusion over 2 h into a radial vein. One monkey in the low-dose group received, along with the unlabelled hR1x-2, 25.5 microCi/kg of the test material internally labelled with [35S]cysteine. Immunoreactive hR1x-2, as measured by enzyme-linked immunosorbent assay, appeared in all fetuses within 30 min (the first sampling time) of beginning the infusions. Peak fetal plasma levels of hR1x-2 were only 0.8-1.5% of the maternal values. Only 8-15% of the fetal serum radioactivity was hR1x-2. Radioactivity from maternal urine pooled over the 4-h experiment did not elute at the volume corresponding to hR1x-2, but near the column volume.

Intrarenal renin-angiotensin system in primitive vertebrates.

Teleost fishes, which have a simpler nephron structure and lack the macula densa, respond to lowered blood pressure by releasing renin. Inhibition of the angiotensin-converting enzyme decreases the resting level of blood pressure, suggesting that the RAS may participate in control of blood pressure in fish. Glomerulotubular balance is poorly developed, and GFR is readily increased by an increase in renal perfusion pressure. It is not clear at present whether angiotensin is involved physiologically in intermittency of glomerular filtration, or whether it controls GFR through its action on systemic blood pressure. Birds appear to have an intermediate form between primitive vertebrates and mammals in terms of morphologic structure of the JG apparatus and nephrons, and in renal function. Fowl, in which angiotensin causes biphasic depressor and pressor responses, do not respond to acute hypotension or hypovolemia by releasing renin unless blood pressure remains low. Unilateral infusion of hypertonic saline into the renal portal system, which perfuses the peritubular sinusoid, increases urinary excretion of sodium chloride in the infused kidney, accompanied by mild diuresis. The slight but significant decrease in PRA occurs after portal infusion of hypertonic saline. Further investigation will be necessary to determine on an individual nephron basis whether an increased tubular sodium or chloride load may alter GFR by a possible tubuloglomerular feedback mechanism.

Acute effects of marijuana smoke on complex operant behavior in rhesus monkeys.

The acute behavioral effects of marijuana smoke were assessed in rhesus monkeys using a battery of food-reinforced complex operant tasks that included incremental repeated acquisition (IRA, n = 9), conditioned position responding (CPR, n = 8), progressive ratio (PR, n = 8), delayed matching to sample (DMTS, n = 6), and temporal response differentiation responding (TRD, n = 3). Marijuana or placebo smoke was delivered by a specialized face mask 15-min before sessions at exposure levels of 1, 5, 10, and 15 puffs (35cc/puff) or one cigarette smoked to a butt length of approximately 10 mm (approximately 20 puffs). Marijuana smoke caused significant disruptions of performance in all tests except PR after exposure to 10 or more puffs. Generally, response rates decreased or latencies to respond increased. Performance in the PR test was not consistently affected by marijuana exposure. Accuracy of responding was not altered by marijuana smoke at doses lower than those that decreased response rates in the IRA or CPR tests. In the three animals performing under all five schedules, the relative sensitivities for detecting marijuana behavioral effects were DMTS = TRD greater than IRA = CPR greater than PR. These results suggest that performance under operant schedules that are thought to represent some aspect of time perception, short-term memory, learning, motivation, and position discrimination show differential sensitivity to disruption by marijuana smoke, a finding similar to that noted previously for iv THC administration.

Behavioral and neurochemical effects of orally administered MDMA in the rodent and nonhuman primate.

MDMA (methylenedioxymethamphetamine) is a recreational drug of abuse known as "Ecstasy" which markedly decreases regional brain serotonin (5-HT) content and produces 5-HT nerve terminal degeneration in forebrain areas of the rat. In order to determine the acute and chronic behavioral effects of MDMA, adult rats were given MDMA at 0, 5 or 10 mg/kg, po for 4 consecutive days. Alternatively, parachloroamphetamine (PCA) at 5 mg/kg was administered under the same regimen. Within 30 min after the first dose, the MDMA-treated rats exhibited the serotonin motor syndrome consisting of straub tail and splayed hindlimbs comparable to that seen in the PCA-treated rats. This serotonin motor syndrome, with a duration of about 2 hr, was less pronounced after subsequent doses. At 2-4 wk after the last dose, no significant differences between control and treated rats were seen in emergence, hot plate response, auditory startle response or complex maze behavior even though a significant dose-related decrease (50%) in 5-HT concentration was observed in the frontal cortex and hippocampus of these rats 4 wks after the last dose. Adult female monkeys dosed po with 5 or 10 mg/kg of MDMA twice/day for 4 consecutive days demonstrated no spontaneous behavioral changes or weight loss compared to controls, but forebrain 5-HT concentration was reduced by 80% 1 mon after dosing. These data indicate that at doses only 2-3 times the human dose, MDMA produces significant forebrain 5-HT decreases but does not produce detectable residual behavioral alterations as assessed by these behavioral paradigms.

No increase in carcinogen-DNA adducts in the lungs of monkeys exposed chronically to marijuana smoke.

Rhesus monkeys exposed to marijuana smoke either 7 or 2 days/weeks (HI and LO groups, respectively), or ethanol-extracted marijuana smoke for 7 days/week (EM) or sham treatment (SH) for 1 year were sacrificed 7 months following the last exposure. Pulmonary levels of carcinogen-DNA adducts were determined. Although mean or median adduct levels were not statistically different, 15 of 22 adduct measures were highest in the EM group and lowest 12 of 22 times in the SH group. The levels of aromatic carcinogen-DNA adducts seem no higher in the lungs of animals exposed to marijuana smoke than in untreated animals. Ethanol-extracted marijuana may have effects greater than marijuana itself.

Pharmacokinetics of doxylamine, a component of Bendectin, in the rhesus monkey.

The elimination of doxylamine and metabolites was determined after iv administration of [14C]doxylamine succinate at 0.7 and 13.3 mg/kg to the adult female rhesus monkey. Although the total recovery of radioactivity was the same for the low- and high-dose studies (90.2%), the rate of plasma elimination of doxylamine and its demethylated metabolite (desmethyldoxylamine) was slower for the high dose group. The 24 hr urinary excretion of doxylamine metabolites, desmethyl- and didesmethyldoxylamine, was significantly increased and the polar doxylamine metabolites were significantly decreased as the iv doxylamine succinate dose was increased. The plasma elimination of gas chromatograph (GC)-detected doxylamine was determined after oral administration of Bendectin (doxylamine succinate and pyridoxine hydrochloride) at 7, 13.3, and 27 mg/kg to adult female rhesus monkeys. As the dose increased, the clearance of doxylamine decreased. A statistically evaluated fit of the oral data to a single-compartment, parallel first-order elimination model and a single-compartment, parallel first- and second-order (Michaelis-Menten) elimination model indicated that the more complex model containing the second-order process was most consistent with the observed elimination data.

Pharmacokinetics of cocaine in pregnant and nonpregnant rhesus monkeys.

To determine pharmacokinetic parameters for cocaine in rhesus monkey plasma, samples were taken over several hours after i.m. administration of cocaine plus a tritiated cocaine tracer. Cocaine and its metabolites, benzoylecgonine and norcocaine, were isolated via HPLC and quantitated using liquid scintillation spectrometry. Pregnant subjects were dosed with cocaine at 0.3 (n = 3) or 1.0 (n = 3) mg/kg, whereas nonpregnant female subjects were dosed with 1.0 mg/kg (n = 3). For the pregnant subjects, pharmacokinetic studies were conducted on about gestational day 125 and areas under the concentration versus time curve (AUCs, ng/mL x h) were 64 +/- 26 (+/- SEM) and 143 +/- 12; half-lives (t1/2s, h) were 1.9 +/- 0.6 and 1.1 +/- 0.1 after 0.3 and 1.0 mg/kg i.m., respectively. For nonpregnant subjects dosed acutely with 1.0 mg/kg, the AUC was 262 +/- 63 and the t1/2 was 1.4 +/- 0.3. There appear to be few differences in the pharmacokinetic parameters of cocaine and benzoylecgonine between pregnant and nonpregnant monkeys in this study.

Chronic marijuana smoke exposure in the rhesus monkey. IV: Neurochemical effects and comparison to acute and chronic exposure to delta-9-tetrahydrocannabinol (THC) in rats.

THC is the major psychoactive constituent of marijuana and is known to produce psychopharmacological effects in humans. These studies were designed to determine whether acute or chronic exposure to marijuana smoke or THC produces in vitro or in vivo neurochemical alterations in rat or monkey brain. For the in vitro study, THC was added (1-100 nM) to membranes prepared from different regions of the rat brain and muscarinic cholinergic (MCh) receptor binding was measured. For the acute in vivo study, rats were injected IP with vehicle, 1, 3, 10, or 30 mg THC/kg and sacrificed 2 h later. For the chronic study, rats were gavaged with vehicle or 10 or 20 mg THC/kg daily, 5 days/week for 90 days and sacrificed either 24 h or 2 months later. Rhesus monkeys were exposed to the smoke of a single 2.6% THC cigarette once a day, 2 or 7 days a week for 1 year. Approximately 7 months after the last exposure, animals were sacrificed by overdose with pentobarbital for neurochemical analyses. In vitro exposure to THC produced a dose-dependent inhibition of MCh receptor binding in several brain areas. This inhibition of MCh receptor binding, however, was also observed with two other nonpsychoactive derivatives of marijuana, cannabidiol and cannabinol. In the rat in vivo study, we found no significant changes in MCh or other neurotransmitter receptor binding in hippocampus, frontal cortex or caudate nucleus after acute or chronic exposure to THC. In the monkey brain, we found no alterations in the concentration of neurotransmitters in caudate nucleus, frontal cortex, hypothalamus or brain stem.(ABSTRACT TRUNCATED AT 250 WORDS)

Marijuana exposure and pulmonary alterations in primates.

As part of a large multidisciplinary study, we examined lungs from 24 periadolescent male rhesus monkeys that were sacrificed seven months after daily marijuana smoke inhalation of 12 months duration. Animals were divided into four exposure groups: A) high-dose (one marijuana cigarette 7 days/week), B) low-dose (one marijuana cigarette 2 days/week and sham smoke 5 days/week), C) placebo (one extracted marijuana cigarette 7 days/week), and D) sham (sham smoke 7 days/week). Lungs, removed intact, were formalin inflated, sectioned and examined. Several pathological alterations, including alveolitis, alveolar cell hyperplasia and granulomatous inflammation, were found with higher frequency in all cigarette-smoking groups. Other alterations, such as bronchiolitis, bronchiolar squamous metaplasia and interstitial fibrosis, were found most frequently in the marijuana-smoking groups. Alveolar cell hyperplasia with focal atypia was seen only in the marijuana-smoking animals. These changes represent mostly early alterations of small airways. Additional follow-up studies are needed to determine their long-term prognostic significance.

Oral administration of 3,4-methylenedioxymethamphetamine (MDMA) produces selective serotonergic depletion in the nonhuman primate.

MDMA (3,4-methylenedioxymethamphetamine) has been reported to produce serotonergic depletion in nonhuman primates at doses as low as 2.5 mg/kg (1-2 times the typical human dose). The current study evaluated the dose-response relationships of MDMA (1.25-20.0 mg/kg) using regional concentrations of serotonin (5-HT) and its metabolite, 5-hydroxyindoleacetic acid (5-HIAA), and home cage behavior as endpoints. Adult female rhesus monkeys (n = 16) were treated orally with 0, 1.25, 2.5, or 20.0 mg/kg MDMA twice daily for 4 consecutive days. Eighteen behaviors were measured in the home cage prior to, during, and after MDMA treatment. One month after the last dose, the animals were sacrificed and brains dissected into several regions for neurochemical analyses. 5-HT and 5-HIAA were analyzed via HPLC/EC. The lower doses of MDMA (1.25 and 2.5 mg/kg) did not significantly alter 5-HT or 5-HIAA concentrations in any brain region except hippocampus in which 5-HT concentrations were decreased after 2.5 mg/kg. MDMA at 20.0 mg/kg significantly decreased 5-HT and 5-HIAA concentrations in several cortical and midbrain structures. However, 5-HT and 5-HIAA concentrations in brain stem and hypothalamus were not significantly altered after any dose of MDMA. Combined with previous data from this laboratory, these results indicate that the decreased concentrations of 5-HT and 5-HIAA in selected brain regions show a selective dose-response relationship for MDMA-induced neurotoxicity as measured by serotonergic depletion in the nonhuman primate.

Metabolism of 14C-labeled doxylamine succinate (Bendectin) in the rhesus monkey (Macaca mulatta).

The time-course of the metabolic fate of [14C]doxylamine was determined after the p.o. administration of 13 mg/kg doxylamine succinate as Bendectin plus [14C]doxylamine succinate to the rhesus monkey. Urine and plasma samples were analyzed by reversed-phase high performance liquid chromatography (HPLC), chemical derivatization, and mass spectrometry. The cumulative 48-hr urinary metabolic profile contained 81% of the administered radiolabeled dose and consisted of at least six radiolabeled peaks. They were peak 1: unknown polar metabolites (8% of dose); peak 2: 2-[1-phenyl-1-(2-pyridinyl)ethoxy] acetic acid, 1-[1-phenyl-1(2-pyridinyl)ethoxy] methanol, and another minor metabolite(s) (31%); peak 3: doxylamine-N-oxide (1%); peak 4a: N,N-didesmethyldoxylamine (17%); peak 4b: doxylamine (4%); and peak 5: N-desmethyldoxylamine (20%). The plasma metabolic profile was the same as the urinary profile except for the absence of doxylamine-N-oxide. The maximum plasma concentrations and elapsed time to attain these concentrations were as follows. Peak 1: 540 ng/mL, 4 hr; peak 2: 1700 ng/mL, 1 hr; peak 4a: 430 ng/mL, 4 hr; peak 4b: 930 ng/mL, 2 hr; and peak 5: 790 ng/mL, 2 hr. These data suggest that in the monkey, doxylamine metabolism follows at least four pathways: a minor pathway to the N-oxide; a minor pathway to unknown polar metabolites; a major pathway to mono- and didesmethyldoxylamine via successive N-demethylation; and a major pathway to side-chain cleavage products (peak 2) via direct side-chain oxidation and/or deamination.

Verocytotoxin-producing Escherichia coli O157 on a farm open to the public: outbreak investigation and longitudinal bacteriological study.

Verocytotoxin-producing Escherichia coli (VTEC) O157 phage type 2 (PT2) was isolated from three calves and two goats on a farm open to the public. Phenotypic and DNA-based typing showed that the strains were identical or very closely related to those obtained from an outbreak of VTEC O157 infection in two separate family groups who visited the farm. No VTEC O157 PT2 was isolated again from the farm during a 12-month longitudinal bacteriological study undertaken after the infected animals had been removed. However, phenotypically and genotypically indistinguishable VTEC O157 PT2/28 strains were detected in two of 474 faecal samples collected at monthly visits from 15 species of animals of various ages. The two isolates were obtained from calves from different sources sampled 146 days apart, suggesting that the infection had persisted on the farm although it was not detected in the other species. The same strain was subsequently isolated from another calf housed in the same pen as one of the infected calves. The longest period during which the organism was excreted was seven days. No VTEC O157 was isolated either from 204 replacement animals (including 138 orphan lambs and 10 calves) brought in from various sources, and sampled while they were kept in isolation for two weeks before being introduced to the farm, or from environmental samples. During the study a visitor became ill with VTEC O157 PT2. However, the isolate was distinct from those recovered from the farm and there was no evidence to suggest that the visit was the source of the infection.