Influence of local and neutral anaesthetics on the polymorphic phase preferences of egg yolk phosphatidylethanolamine.

(1) The polymorphic phase preferences of egg phosphatidylethanolamine have been examined in the presence of normal alcohols and alkanes of varying chain length, as well as charged amine anaesthetics. (2) It is shown that the charged anaesthetics, ethanol and butanol can stabilize a bilayer arrangement for egg phosphatidylethanolamine. In contrast, longer chain (C greater than or equal to 6) normal alcohols and alkanes induce the hexagonal (HII) phase. (3) The relative potency of local anaesthetics in vitro (chlorpromazine, dibucaine, tetracaine and procaine) is mirrored by their relative ability to stabilize bilayer structure for hydrated egg phosphatidylethanolamine. Further, the aqueous concentrations of anaesthetic required to affect phospholipid polymorphism is sensitive to the lipid composition. For example, the inclusion of 20 mol% egg phosphatidylserine in egg phosphatidylethanolamine dispersions can reduce the aqueous concentrations of dibucaine required to induce appreciable bilayer stabilization effects from 5.0 mM to 0.5 mM. (4) It is suggested that the ability of amphipathic molecules such as anaesthetics to influence phosphatidylethanolamine polymorphism arises from their molecular shape. The possibility that anaesthetic molecules may exert their effects by virtue of this shape property is raised.

Tobacco-specific nitrosamines in the saliva of Inuit snuff dippers in the Northwest Territories of Canada.

Levels of tobacco-specific nitrosamines (TSNA), nicotine and cotinine were estimated in the saliva of 20 snuff dippers (Inuit, Northwest Territories, Canada). Levels of N'-nitrosonornicotine (NNN), 4-(methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone (NNK), and N-nitrosoanatabine (NAT) plus N-nitrosoanabiasine (NAB) found in the saliva following a 15-min period of keeping 0.5-1.5 g of moist snuff in the gingival groove are considerable: 115-2610 ppb NNN, 123-4560 ppb NAT + NAB, and up to 201 ppb NNK. The amount of TSNA in the saliva increases with the length of time that the snuff is kept in the mouth. The estimated total amount of 444 micrograms TSNA, the largest part of which will be swallowed, exceeds by far the amounts of nitrosamines ingested through drinking beer (0.34 micrograms/day), eating cured meat products (0.17 micrograms/day), or using cosmetics (0.41 micrograms/day). The relatively high levels of potentially carcinogenic TSNA in the saliva, together with the current popularity of snuff usage by teenagers, is of particular concern.

Beta-carotene levels in exfoliated human mucosa cells following its oral administration.

Beta-carotene levels of exfoliated oral mucosa cells can be increased severalfold by the oral administration of this provitamin. Beta-carotene was estimated by HPLC analysis in pronase-treated exfoliated cells obtained by brushing the entire oral mucosa with a toothbrush. A small percentage of individuals did not respond with an increase of beta-carotene in their mucosa cell in spite of a relatively large intake of the provitamin (360 mg in 4 days, or 2880 mg in 16 weeks, respectively). Levels of beta-carotene in the mucosa cells are affected by the concurrent administration of vitamin A: 0.27 ng beta-carotene per 10(6) cells in the placebo group, 1.79 ng following the intake of beta-carotene (180 mg/week for 16 weeks), and 4.29 ng after beta-carotene (180 mg/week for 16 weeks) plus vitamin A (100,000 IU/week for 16 weeks) consumption. The considerable variations in tissue levels of beta-carotene following its oral administration must be taken into account when cancer intervention trials using this agent are designed and evaluated.

Response of oral leukoplakias to the administration of vitamin A.

Tobacco/betel nut chewers (Kerala, India) with well-developed oral leukoplakias were chosen for a short-term intervention trial of vitamin A therapy. Participants were randomly distributed into two groups, one receiving 200,000 IU vitamin A per week (0.14 mg/kg body wt/per day) for 6 months, and the other receiving placebo capsules. Their cancer-causing habit, which can be quantitated (an average of 13.1 betel quids/day, 26.1 min/quid), did not change during the trial period. The 6-month oral administration of vitamin A caused complete remission in 57.1% of participants, and a total suppression of the development of new leukoplakias in all chewers receiving vitamin A (n = 21), as compared to 3% and 21%, respectively, in the placebo group (n = 33). The results were substantiated by examining the histological and cytological changes on small biopsies which were taken at the onset and at the completion of the trial period. Over the 6-month period of vitamin A administration, the number of layers of spinous cells decreased in 85% of the participants, the loss of polarity of basal cells was reduced from 72.2% to 22.2% of chewers, subepidermal lymphocytic infiltration was greatly diminished from 66.7% to 5.5% of chewers, and nuclei with condensed chromatin disappeared from the epidermal layer (72.2% before to 0% at the end of the trial).

A pilot beta-carotene intervention trial with Inuits using smokeless tobacco.

The frequency of exfoliated cells with micronuclei (MNC) was used to estimate the genotoxic effect of smokeless tobacco (snuff) on the oral mucosa and to follow the response to the administration of beta-carotene (180 mg/week, given twice weekly in 6 capsules of 30 mg each). The pilot trial was carried out with Inuits in Gjoa Haven, Northwest Territories, Canada. Their traditional diet, which is rich in caribou and seal meat and liver but low in vegetables and fruits, leads to "normal" serum levels of retinol (447 ng/ml in non-users of tobacco and 463 ng/ml in tobacco users) but low levels of beta-carotene (57 ng/ml for non-users of tobacco and 47 ng/ml for users). Prior to the twice-weekly administration of beta-carotene, the frequency of MNC was 1.87% +/- 0.92 (n = 23) in the mucosa of the lower gingival groove where the tobacco was usually kept. It decreased significantly (P less than 0.001) to 0.74% +/- 0.42 following the 10-week oral administration of beta-carotene capsules. The frequency of MNC did not change significantly in the group receiving a placebo and in snuff users who received no treatment over the 10-week trial period. The size and morphological appearance of the typical snuff-related, whitish, wrinkled patches of the mucosa where the tobacco was kept was not affected by the 10-week treatment with beta-carotene. Similarly, no reduction was observed in the frequency of anucleated, exfoliated mucosa cells. Beta-carotene appears to be an efficient inhibitor of MNC in the oral mucosa of snuff users who do not suffer from any vitamin A deficiency and who have "normal" levels of retinol.

Beta-carotene levels in exfoliated mucosa cells of population groups at low and elevated risk for oral cancer.

Beta-carotene was estimated in exfoliated oral mucosa cells in groups of individuals at various risks for oral cancer. Approximately 4 X 10(6) exfoliated cells were collected from each subject by brushing the oral mucosa. Cell pellets were hydrolyzed with pronase and then with KOH/methanol. Beta-carotene was extracted with hexane, separated by reverse-phase HPLC, and detected at 450 nm. Mean beta-carotene levels in exfoliated cells were 0.08 ng/10(6) cells for 56 heavy consumers of alcoholic beverages (150 g or more per week), 1.36 ng/10(6) cells for 28 Seventh Day Adventists (all abstainers from alcohol, tobacco and meat consumption), 1.39 ng/10(6) cells for 55 lacto-vegetarians of the International Society for Krishna Consciousness (ISKC) (abstainers from alcohol and tobacco), and 1.08 ng/10(6) cells for 61 representatives of a "Western" life-style pattern (64% consumed the equivalent of at least one bottle of wine or 7 bottles of beer per week, and all were non-smokers). If the heavy alcohol consumers (males) are matched to non-drinking males of comparable age, the mean beta-carotene values are 0.08 ng versus 1.24 ng/10(6) cells. The possible involvement of the low levels of beta-carotene in the mucosa of heavy alcohol drinkers in increased sensitivity towards the carcinogenic and genotoxic activity of cigarette smoking plus alcohol ingestion is discussed.

The effect of dietary factors on nitrosoproline levels in human urine.

The effect of dietary components on the levels of nitrosoproline ( NPRO ) excreted over a 24 h period in the urine was examined in volunteers ingesting known amounts of various food products. The ingestion of nitrite-preserved meats (85-170 g per meal), including canned, rolled or Yunnan ham, cured pork, luncheon meat, and various Chinese and European-style sausages, led to urinary NPRO excretion levels ranging from 2.5 to 78.5 micrograms/24 h, whereas the consumption of non-preserved meat and fish products, including chicken, herring, salmon, shrimp, ground beef (hamburger), pork chops and beef liver, led to relatively low NPRO excretion levels, ranging from 0.0 to 0.8 micrograms/24 h. The urinary NPRO levels of 22 vegetarians and 14 lacto-vegetarians averaged 0.8 and 1.4 micrograms/24 h, respectively. A change from a nitrite-preserved meat diet to a vegetarian diet was accompanied by an approximately six-fold reduction in urinary NPRO levels; however, these remained above control levels for at least 3 days following the dietary change. The relatively high NPRO levels following the ingestion of nitrite-preserved meats could not be reduced by nitrite-trapping chemicals, including ascorbic acid, ferulic acid, caffeic acid, or phenolic-containing mixtures such as coffee and tea, which were effective in suppressing endogenous NPRO formation following the intake of nitrate and proline. The high urinary NPRO levels after ingestion of preserved meat products appear to be due to the consumption of preformed NPRO . An understanding of the relative contribution of preformed and endogenously formed nitrosamines appears to be essential when designing dietary intervention programmes.

Remission of oral leukoplakias and micronuclei in tobacco/betel quid chewers treated with beta-carotene and with beta-carotene plus vitamin A.

Fishermen from Kerala (India) who chewed tobacco-containing betel quids daily (17.2 +/- 9.6 quids per day) and had well-developed oral leukoplakias with elevated frequencies of micronucleated cells participated in a short-term intervention trial. Beta-carotene (180 mg/week) (Group I), beta-carotene (180 mg/week) plus vitamin A (100,000 IU/week) (Group II), and placebo (Group III) capsules were given twice weekly for 6 months under strict supervision. The remission of oral leukoplakias, the inhibition of new leukoplakias, and the reduction of micronucleated oral mucosal cells were recorded at the 3rd and 6th months of the trial period. After 3 months, the frequency of micronucleated cells was significantly reduced in Group I (from 4.09% to 1.1% in areas of leukoplakia, and from 4.1% to 1.0% in the normal mucosa). At this time, remission of oral leukoplakias did not differ significantly from that observed in the placebo group. After 6 months of treatment, remission of leukoplakias in Group I (14.8%) and Group II (27.5%) differed significantly from that seen in Group III (3.0%). The development of new leukoplakias during the 6-month period was strongly inhibited in Group II (7.8%), and to a lesser degree in Group I (14.8%), as compared to Group III (21.2%). During the trial period, all participants continued to chew tobacco-containing betel quids in their accustomed manner. Thus, remission and inhibition of new oral leukoplakias and reduction of micronucleated mucosal cells occurred in the groups receiving beta-carotene and beta-carotene plus vitamin A during the continuous presence of carcinogens derived from tobacco and areca nut.