Formation of N-trimethyl-N-nitrosourea in the gastric lumen of the fistulated pig.

The formation of N-trimethyl-N-nitrosourea (TMNU) in the stomach of full-sized gastric-fistulated pigs was determined. Nitrite was added to the stomach in amounts that have been reported to occur in the human stomach (25-375 mumol). The vehicle was an 'artificial meal' made up of synthetic gastric juice.

Proliferative and neoplastic lesions in the rodent nasal cavity.

Proliferative lesions in the rodent nasal cavity are reviewed; attempt was made to compare species affected, sex differences, strain differences, route of administration and tumor types occurring both spontaneously and after induction by different chemicals. This review is not meant to be all inclusive but to be representative of observed trends. Our general conclusions in this paper are that: 1) spontaneous nasal tumors in rodents are very rare; 2) spontaneous nasal tumors in rats are most often squamous cell tumors, whereas hemangiomas or respiratory adenomas predominate in mice and squamous cell tumors are rare; 3) rats are usually more susceptible to the induction of epithelial tumors of the nasal cavity than mice; 4) chemically-induced hemangiomas and hemangiosarcomas of the nasal cavity have only been reported in mice; 5) tumors of the olfactory epithelium are almost uniformly malignant and invasive, while nonsquamous tumors of the respiratory epithelium are typically less invasive; 6) chemically-induced tumors of the olfactory region, either mesenchymal or epithelial, do not always require an inhalation route of exposure but may occur by systemic targeting of this region; and 7) chemicals inducing tumors in the olfactory region often produce a variety of tumor morphologies in this location as well as squamous and polypoid tumors of the transitional region.

Growth of Listeria monocytogenes Scott A, serotype 4 and competitive spoilage organisms in raw chicken packaged under modified atmospheres and in air.

The development of Listeria monocytogenes Scott A, serotype 4 and aerobic plate counts on minced raw chicken were determined independently at 4, 10 and 27 degrees C. Samples were packaged in flexible film under two modified atmospheres (one containing oxygen and one containing no oxygen) or air. The anaerobic modified atmosphere (75:25, CO2:N2) resulted in the failure of both the aerobic plate counts and L.

Duration of phasic electrical activity of the hypothalamic gonadotropin-releasing hormone pulse generator and dynamics of luteinizing hormone pulses in the rhesus monkey.

The secretion of luteinizing hormone (LH) by the pituitary gland is a pulsatile phenomenon. In the rhesus monkey, each pulse of LH in the peripheral circulation is associated with a characteristic increase in multiunit electrical activity (MUA) recorded from the medial basal hypothalamus. These "volleys" of electrical activity initiate the release of gonadotropin-releasing hormone (GnRH) into the pituitary portal circulation from the terminals of neurosecretory cells.

Organic toxicants and mutagens in ashes from eighteen municipal refuse incinerators.

Ashes, obtained from about one-fourth of the operating municipal refuse incinerators in the United States, were analyzed for a range of organic toxicants and mutagens. Thirty percent of the ash samples, which consisted of bottom ash or bottom ash-fly ash mixtures, contained 20-74% organic matter. Thirty percent of the ashes contained direct-acting and/or promutagens which revertedSalmonella typhimurium TA98 or TA100.

Quantitative estimates of N-nitrosotrimethylurea formation in the porcine stomach.

Gastric formation of N-nitrosotrimethylurea (NTMU) was quantified by repeated sampling of the gastric contents of full-sized fistulated pigs after the addition of 250 mumol trimethylurea (TMU) and 25-125 mumol nitrite. Maximum gastric nitrite concentration was 100-500 microM based on the gastric volume and amount of added nitrite, which is within the range reported in human gastric contents. The total amount of NTMU formed over time was quantified by estimating both the NTMU concentration and gastric volume using multiple additions of polyethylene glycol.

Duration and frequency of multiunit electrical activity associated with the hypothalamic gonadotropin releasing hormone pulse generator in the rhesus monkey: differential effects of morphine.

The effects of morphine on the frequency and duration of the characteristic bursts or 'volleys' of multiunit electrical activity (MUA) associated with pulsatile pituitary luteinizing hormone (LH) secretion were studied in unanesthetized ovariectomized rhesus monkeys bearing bilateral arrays of electrodes implanted in the mediobasal hypothalamus. Morphine administration resulted in a dose-dependent decrease in MUA volley duration and frequency. When morphine was infused at 10 micrograms/kg/h, the inhibiting effect on volley duration was observed without a change in volley frequency.

Corticotropin-releasing factor and gonadotropin-releasing hormone pulse generator activity in the rhesus monkey. Electrophysiological studies.

The effect of corticotropin-releasing factor (CRF) on the hypothalamic gonadotropin-releasing hormone (GnRH) pulse generator, the central neuronal system governing pulsatile pituitary luteinizing hormone (LH) secretion, was studied electro-physiologically in 6 ovariectomized rhesus monkeys bearing bilateral arrays of recording electrodes implanted in the mediobasal hypothalamus. 'Volleys' of increased multiunit activity (MUA) were recorded for 6-10 h in animals placed in primate chairs. The circulating concentrations of LH and cortisol were determined by radioimmunoassay in blood samples taken every 10 min for 3-4 h prior to the administration of CRF (200 micrograms, i.

Chromosome damage in rat pulmonary alveolar macrophages following ozone inhalation.

To determine whether ozone is clastogenic at environmentally relevant exposure levels, rats were exposed for 6 h to 0.0, 0.12, 0.

Murine susceptibility to street rabies virus is unrelated to induction of host lymphoid depletion.

The mechanism and cellular targets of mononuclear cell depletion were investigated in strains of mice susceptible or resistant to lethal infection with a virulent street rabies virus (SRV). Significant depletion was evident in the thymus of all infected animals at approximately 5 days postinfection and subsequently involved the spleen and lymph nodes in mice developing clinical signs of rabies. Immunofluorescent analyses of lymphocyte subsets in depleted spleens revealed that cell losses were non-selective since the relative proportions of K+, Thy-1+, Lyt-1+, and Lyt-2+ cells remained unchanged.

Proliferative responses of rat nasal epithelia to ozone.

The epithelium of the female Fischer 344/N rat anterior nasal cavity was examined and found to be composed of four types of epithelia: squamous, ciliated respiratory, nonciliated cuboidal/transitional, and olfactory. DNA replication in these tissues was monitored by bromodeoxyuridine (BrdUrd) incorporation. Labeled cells were identified using a monoclonal antibody recognizing BrdUrd.

Assessment and management of food safety risks.

The scientific community believes that the U.S. food supply is as safe as any.

In vivo inhibition of N-nitrosodimethylamine metabolism by 4-methylpyrazole: a model for endogenous nitrosation.

The endogenous formation of N-nitrosodimethylamine (NDMA) was investigated in the ferret by inhibiting metabolism and monitoring urinary NDMA levels. The addition of 1.0 mg/ml of 4-methylpyrazole (4-MP) to the drinking water was sufficient to allow a 13% urinary recovery of a 4.

Comparison of acute ozone-induced nasal and pulmonary inflammatory responses in rats.

The centriacinar pulmonary lesion induced by ozone has been extensively characterized, but little is known about the effects of this oxidant gas in the upper airways. The present study was designed to compare the effects of acute ozone exposure in the nose and lungs of rats. We examined the cellular inflammatory responses in the nasal cavity and lower respiratory tract by means of nasal and bronchoalveolar lavage and morphometric quantitation of neutrophils within the nasal mucosa and pulmonary terminal bronchioloalveolar duct regions (i.

Nitrite-cured meats as a source of endogenously and exogenously formed N-nitrosoproline in the ferret.

Nitrite-cured meat containing 120 mg Na15NO2/kg was fed to male ferrets (Mustela putorius furo). During consumption of the meat, the animals were dosed orally with 0.87 mmol [2-2H]proline.

Photolytic interface for high-performance liquid chromatography--chemiluminescence detection of non-volatile N-nitroso compounds.

A photolytic interface between high-performance liquid chromatography (HPLC) and a chemiluminescence detector has been developed for the trace detection of non-volatile N-nitroso compounds in biological matrices. A chromatographic effluent containing separated N-nitrosoamino acids and N-nitrosamides is introduced into a glass coil with a purge stream of He and irradiated with ultraviolet light. Nitrogen oxide, cleaved by photolysis, is separated rapidly from the solvent through a series of cold traps and carried by the He into the reaction chamber of a chemiluminescence detector.

Response of rat alveolar macrophages to ozone: quantitative assessment of population size, morphology, and proliferation following acute exposure.

The purpose of this study was to evaluate the in vivo effects of an acute exposure to low levels of ozone on rat pulmonary alveolar macrophages (PAM). Fisher 344 rats exposed to 0.0, 0.

Effects of 0.12 and 0.80 ppm ozone on rat nasal and nasopharyngeal epithelial mucosubstances: quantitative histochemistry.

The present study was designed to characterize the quantity of mucosubstances in surface epithelia of the rat nasal cavity and nasopharynx after short-term ozone exposure. Rats were exposure. Nasal cavities were processed for morphometric analysis of intraepithelial mucosubstances.

Preformed N-nitroso compounds in foods and beverages.

Most western-style foods have been analysed for the presence of volatile N-nitrosamines. Relatively few foods consistently contain detectable (greater than 0.1 microgram/kg) amounts of volatile N-nitrosamines.

Quantitation of a murine lung endothelial cell protein, P112, with a double monoclonal antibody assay.

Two monoclonal antibodies (MoAb) have been isolated from two different F344 rats immunized with normal BALB/c mouse lung homogenates. The MoAbs 273-34A and 411-201B demonstrate similar staining properties when used in immunohistochemistry and have been shown to bind to endothelial cells in the lung using immunogold electron microscopy. Radiolabeled MoAb 273-34A injected intravenously localizes rapidly to lung.

Antibodies to mouse lung capillary endothelium.

We are interested in developing monoclonal antibodies (MoAbs) that recognize specific cell types in the lung of BALB/c mice. Normal mouse lung homogenate was used to immunize F344 rats and hybridomas were produced by fusion of rat spleen cells with mouse myeloma SP 2/0. Two hybridomas were selected which produced MoAbs active in immunohistochemistry of lung cells.

In vivo effects of transient neutrophil influx on nasal respiratory epithelial mucosubstances. Quantitative histochemistry.

Certain inhaled toxicants are known to induce mucous hypersecretion in the respiratory epithelium. This secretory change may be a direct effect of the toxicant or an indirect effect of the concomitant inflammatory response. The present study was designed to determine by quantitative histochemistry whether the influx of neutrophils through the nasal respiratory epithelium would induce significant quantitative changes in the amount of intraepithelially stored mucosubstance.