N-nitrosamine analysis in foods: N-nitrosoamino acids by high-performance liquid chromatography/thermal energy analysis and total N-nitroso compounds by chemical denitrosation/thermal energy analysis.

The total N-nitroso content of foods can be measured by chemical denitrosation and chemiluminescent detection of the eliminated nitric oxide. Appropriate procedures substantially reduce the 'system response' to the denitrosating agent, so that N-nitroso group contents down to 10 micrograms/kg can be measured on a one-gram sample. Using N-nitrosamine standards added to beer, the coefficients of variation are approximately 10% and 5% at N-nitroso contents of 19 and 94 micrograms/kg, respectively.

A survey of the occurrence of aflatoxin M1 in UK-produced milk for the period 1981-1983.

A UK survey for the occurrence of aflatoxin M1 in bulked dried milks (totalling 277 samples) obtained at monthly intervals from a number of commercial creameries in the UK over a two-year period (1981-1983), showed 98% of the samples to have levels below 0.03 micrograms/kg. For liquid milks sampled from individual farms over the same period (totalling 409 samples), 94% of the samples had aflatoxin M1 levels below 0.

Estimation of nitropolycyclic aromatic hydrocarbons in foods.

A method is described for the sample clean-up and estimation of nitropolycyclic aromatic hydrocarbons (nitro-PAH) in foods. The analysis involves the novel use of a coupled capillary gas chromatograph/thermal energy analyser and provides a detection limit for 1-nitropyrene of 12 pg (equivalent to 0.02 micrograms/kg for a 50-g sample).

Analysis of polycyclic aromatic hydrocarbons in UK total diets.

Analysis of UK total-diet samples for polycyclic aromatic hydrocarbons was carried out using a simplified sample clean-up and a high-performance liquid chromatography dual fluorescence detector system. The results indicate that cereals and oils/fats contribute the major part (approximately one third each) of the polycyclic aromatic hydrocarbons in these total diets. Fruit, sugars and vegetables provide much of the remainder (approximately one quarter) while meat, fish, milk and beverages make relatively minor contributions.

Abnormal ion permeation through cystic fibrosis respiratory epithelium.

The epithelium of nasal tissue excised from subjects with cystic fibrosis exhibited higher voltage and lower conductance than tissue from control subjects. Basal sodium ion absorption by cystic fibrosis and normal nasal epithelia equaled the short-circuit current and was amiloride-sensitive. Amiloride induced chloride ion secretion in normal but not cystic fibrosis tissue and consequently was more effective in inhibiting the short-circuit current in cystic fibrosis epithelia.

Relative ion permeability of normal and cystic fibrosis nasal epithelium.

The raised transepithelial electric potential difference (PD) across respiratory epithelia in cystic fibrosis (CF) has suggested an abnormality in ion permeation. We characterized this abnormality further by measuring in the nasal epithelia of CF and normal subjects the concentration-PD relationship for amiloride, an inhibitor of cell Na+ permeability, and PD responses to superfusion with solutions of different composition. Amiloride was more efficacious in the CF subjects but the ED50 was not different from that of normals (approximately 2 X 10(-6) M).

Long-term organ culture of normal human bladder.

Normal adult human bladder obtained at cystoscopy has been maintained in long-term organ culture. Several media were tested for their ability to maintain viability and normal tissue morphology. The optimum medium was Ham's F-12 nutrient mixture, supplemented with 10% fetal calf serum, hydrocortisone (1 microgram/ml), and FeSO4, (0.

Metabolism of prostaglandin endoperoxide by microsomes from human lung parenchyma and comparison with metabolites produced by pig, bovine, rat, mouse and guinea-pig.

The metabolism of PGH2 by human lung parenchymal microsomes was characterized by radiometric high performance liquid chromatography and compared with metabolism by pig, bovine, rat, mouse, and guinea pig lung microsomes. Microsomes from human lung synthesized 0.74 nmoles/mg protein and 0.

Measurements of transepithelial electric potential differences in the trachea and bronchi of human subjects in vivo.

We measured in vivo in human subjects the airway transepithelial electric potential difference (PD), a parameter that reflects passive ion permeabilities and active ion transport across respiratory epithelia. A high impedance voltmeter was used to measure PDs between a fluid-filled and perfused recording bridge located on the airway surface and a reference bridge in the subcutaneous space. Tracheal PD was a relatively high 32 +/- 5 mV (lumen negative) in subjects younger than 35 yr of age (n = 23).

Urothelial abnormalities in the obstructed bladder.

Bladder mucosa from patients undergoing prostatectomy was examined histologically for evidence of pre-malignant change. The mucosal appearances were compared with tissue taken from control patients without bladder outlet obstruction. The appearances in patients with uncomplicated obstruction and in control patients were found to be similar and dysplastic change was uncommon.

Metabolism and binding of benzo(a)pyrene and 2-acetylaminofluorene by short-term organ cultures of human and rat bladder.

The ability of organ cultures of normal human and rat bladder to metabolize the polycyclic hydrocarbon, benzo(a)pyrene (BP), and the arylamine, 2-acetylaminofluorene, has been studied. Cultures were maintained for 0 to 6 days in a chemically defined medium before incubation with [3H]BP (0.3 to 0.

Increased bioelectric potential difference across respiratory epithelia in cystic fibrosis.

To investigate respiratory epithelial function in cystic fibrosis, we measured the transepithelial electrical potential difference across the upper and lower respiratory mucosa in patients with cystic fibrosis and control subjects. The nasal potential difference in the 24 patients with cystic fibrosis exceeded by more than 3 standard deviations the mean voltage in healthy controls, subjects with other diseases, and subjects heterozygous for cystic fibrosis. Potential differences in lower airways were measured in four patients and were significantly greater than in controls (P less than 0.

Morphometric aspects of ciliary distribution and ciliogenesis in human nasal epithelium.

Observations of freeze-fracture preparations of human nasal epithelium have provided a unique perspective of the spatial distribution of epithelial cell cilia unattainable by more conventional ultrastructural techniques. The initial stages of ciliogenesis were characterized ultrastructurally in these preparations by differentiation of the lumenal aspect of the epithelial cell membrane prior to the emergence and maturation of new cilia. Morphometric analyses of the resultant electron micrographs indicate that the development of an optimal ciliary population during differentiation of ciliated cells may be integral to the adequate functioning of respiratory mucociliary mechanisms.

Measurements of nasal transepithelial electric potential differences in normal human subjects in vivo.

Nasal transepithelial electrical potential difference (PD) was estimated in vivo in normal human subjects. The PD between a bridge perfused with Ringer's solution placed on the nasal mucosal surface and a reference electrode in a subcutaneous space was recorded. The magnitude of the PD depended upon the region of the nasal cavity touched by the exploring bridge.

The evaluation of cefuroxime in the prevention of postoperative infection.

Patients undergoing biliary surgery received either 750 mg cefuroxime i.m. with the premedication and then 8 hourly for 3 days ((group A) or 1.

Effects of the tumor-promoting agent 12-O-tetradecanoylphorbol-13-acetate on normal and "preneoplastic" mouse submandibular gland epithelial cells in vitro.

The effect of the promoting agent 12-O-tetradecanoylphorbol-13-acetate (TPA) was studied on mixed primary cultures of C57BL/Icrf-at mouse submandibular gland and on slowly proliferating preneoplastic epithelial foci derived from such cultures. No cytologic alterations were noted in the TPA-treated epithelium. The development of three-dimensional epithelial ducts occurring between 30 and 60 days in vitro in untreated cultures was markedly inhibited in TPA-treated cultures.

Ultrastructure and biological markers of neoplastic change in adult mouse epithelial cells transformed in vitro.

The ultrastructure and in vitro growth properties of 5 tumorigenic mouse submandibular-gland epithelial cell lines were studied. In all lines, in vitro acinus formation occurred, and well differentiated epithelial cells showing epithelial microvilli and desmosomes and cytoplasmic tonofilaments were present. None of the cells showed specific ultratructural features of the normal differentiated submandibular-gland ducts.

The structure of tumours derived from mouse submandibular gland epithelium transformed in vitro.

The morphology and ultrastructure of 48 primary tumours established from 5 cell lines of adult mouse salivary gland epithelial cells transformed in vitro are described. Tumours from 4 of the cells lines were adenocarcinomas with a wide range of structural variation, and resembled human salivary gland carcinomas. The fifth cell line produced tumours with carcinomatous and sarcomatous elements.

Stages in neoplastic transformation of adult epithelial cells by 7,12-dimethylbenz(a)anthracene in vitro.

Five tumor-producing cell lines were established from explant cultures of adult C57BL mouse submandibular gland. Four lines were from cultures treated for 24 hr on Day 4 of culture with 7,12-dimethylbenz(a)anthracene. Three of these gave rise to adenocarcinomas after transplantation into syngeneic mice; the fourth produced tumors with carcinomatous and sarcomatous areas.