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PubMed1994

A behavioral economic analysis of concurrently available money and cigarettes.

In economic terms, consumption of a reinforcer is determined by its price and the availability and price of other reinforcers. This study examined the effects of response-requirement (i.e., price) manipulations on the self-administration of two concurrently available reinforcers. Six cigarette smokers participated in 4-hr sessions in which money and puffs on a cigarette were concurrently available according to fixed-ratio schedules of reinforcement. Once stable responding was obtained with both reinforcers available at Fixed Ratio 100, the response requirement for one reinforcer was systematically varied (Fixed Ratio 1,000 and 2,500), while the other reinforcer remained scheduled at Fixed Ratio 100. Increasing the fixed-ratio size for a reinforcer decreased its consumption, with a greater decrease occurring for monetary reinforcement. This finding was quantified in economic terms as own-price elasticity, with elasticity coefficients greater for money than cigarettes. The effects of fixed-ratio size on response output also differed across the two reinforcers. Although greater responding occurred for money at Fixed Ratio 100, increases in fixed-ratio size (for money) decreased responding for money, whereas the same increase in fixed-ratio size (for puffs) increased responding for puffs. Finally, increasing the fixed-ratio size for one reinforcer had little effect on consumption of the other concurrently available reinforcer. This finding was quantified as cross-price elasticity, with elasticity coefficients near 0.0 for most subjects, indicating little or no reinforcer interaction. The results indicate that the reinforcing effects of cigarettes and money in the setting studied here differed, and that the effects produced by changing the price of one reinforcer did not interact with the consumption of the other concurrently available reinforcer.

Adolescent↗

PubMed1990

Subjective, social, and physical availability. I. Their interrelationships.

The alcohol availability literature suggests that physical conditions which restrict alcohol availability reduce rates of alcohol consumption. Smart (1980) argued that the availability construct should be expanded to include subjective and social components. It was hypothesized that people who perceived alcohol to be subjectively and socially available would consume more alcohol than those who did not and that physical availability would only indirectly affect consumption. These hypotheses were examined using data from a telephone survey. In Part I, the interrelationships between physical, subjective, and social availability are described. In Part II (this journal, Vol. 25, No. 9), the relationships between these variables and alcohol consumption are explored.

Adult↗

PubMed1992

Effect of processing on availability of essential amino acids in rice flour and cooked rice.

The availability of nitrogen, lysine and nine essential amino acids was determined in rice flour and cooked rice. Lysine availability was determined by the growth response method using regression analysis of body weight gain or moisture gain against lysine consumed from rice flour and cooked rice. The results show a good correlation between lysine consumed and weight gain or moisture gain (r = 0.86 + 0.8) for rats fed cooked rice and fair correlation for those fed rice flour. The results of lysine availability show that cooking increases availability by both ways of calculation. The availability of nitrogen and of essential amino acids was also determined by the balance trial method with rats. Results of balance trial show that cooking has no significant effect on essential amino acids availability. Data for weight gain, food efficiency and PER were significantly decreased by cooking.

Amino Acids, Essential↗

PubMed1978

[Measure of available and blocked lysine in industrial milks].

The classical methods to measure lysine availability give rise to some difficulties in milks due to the presence of deoxyketose-lysine (DOKL). Six methods, one of which measuring the blocked lysine, are studied. Amino acid chromatography gives a too high value of lysine when it is blocked as DOKL, the latter regenerating lysine during acid hydrolysis. The determined lysine does not correspond to the available one. Fluro-dinitro-benzene is not fully specific for free epsilon-NH2 of lysine and the reducing sugars present interfere during the reaction in converting "nitro" into "amino" groups. Guanidization is a specific reaction between the epsilon-NH2 of lysine and O-methyl-isourea with formation of homoarginine. The homarginine, calculated as lysine corresponds to the available lysine. Reduction with sodium borhydride converts the DOKL to a stable compound which, during acid hydrolysis, does not regenerate lysine and does not form furosine. The recovered lysine corresponds to the available one. Our "in vitro" digestion method with simultaneous dialysis enables the determination of available lysine, as the proteolytic enzymes used do not split up the DOKL binding. The liberated lysine corresponds to the available one. The blocked lysine is measured from furosine after acid hydrolysis. A formula, which makes up the level of furosine formation and for lysine regeneration from DOKL, is established.

Amino Acids↗

PubMed1982

Noninvasive assessment of portal-systemic shunting: evaluation of a method to investigate systemic availability of oral glyceryl trinitrate by digital plethysmography.

The systemic availability of oral glyceryl trinitrate may be a measure of the fraction of portal blood bypassing the hepatocytes through portal-systemic shunts. In order to test this hypothesis without the need for blood sampling, measurements of drug concentrations in plasma were replaced by assessments of pharmacologic effects by using digital plethysmography. Dose-response curves resulting from graded intravenous infusions of glyceryl trinitrate (8 and 25 microgram/min) were used as standard of comparison for the pharmacologic response resulting from an oral dose of 800 microgram. In 9 normal volunteers, systemic availability of oral glyceryl trinitrate was 2 +/- 4% SD. In 7 patients with end-to-side portacaval shunts it was 94 +/- 18%, in 3 patients with distal splenorenal shunts 57 +/- 11%, and in 10 patients with cirrhosis of the liver it varied between 15% and 85%. Systemic availability of glyceryl trinitrate was negatively correlated with the initial plasma disappearance rate of sulfobromophthalein (r = -0.72, p less than 0.01). No significant correlation was found with the galactose elimination capacity (r = -0.12, n = 17). The lack of systemic availability of glyceryl trinitrate in healthy volunteers together with an availability close to 100% after end-to-side shunts is compatible with a very high hepatic extraction of the test compound by the normal liver, and with the idea that the systemic availability of of oral glyceryl trinitrate comes close to representing portal-systemic shunting. The procedure is rapid, essentially noninvasive, and well tolerated by patients.

Administration, Oral↗

PubMed1989

Effect of addition of bovine milk and vegetable milks on the in vitro availability of iron from cereal meals.

Studies were carried out on the in vitro availability of iron from a standard cereal meal with and without the addition of bovine milk (BM), groundnut milk (GM) and soybean milk (SM). Further, availability of iron from these milks per se was also investigated. Estimation of the total iron content from BM, GM, and SM revealed that it was highest in case of SM followed by GM and BM. This trend was reversed for percent available iron which was highest for BM followed by GM and SM. The in vitro availability of iron from the cereal meal was low (3.7%). Addition of BM and GM enhanced the availability of iron from the standard meal whereas SM had no particular enhancing quality. The practical implications of the findings for iron nutrition in humans are discussed.

Animals↗

PubMed1987

An equation for the systemic availability of drugs undergoing simultaneous enterohepatic cycling, first-pass metabolism, and intestinal elimination.

A relationship between systemic availability and its determinants has been derived for a physiologically realistic model of drug disposition that includes enterohepatic cycling (EHC), gallbladder emptying (with an arbitrary time course), first-pass metabolism to noncycling metabolites, and fecal excretion. Systemic availability (F) has been shown to be determined by the fraction of the dose initially absorbed (f*a), the fraction of the drug excreted into the GI tract that is reabsorbed with each cycle (fa), the hepatic extraction ratio (E), and the fraction of extracted drug that is transported to the gallbladder for EHC (fg) according to the relationship F = f*a(1 - E)/(1 - fafgE) The implications of the above relationship are that (1) systemic availability is dependent on EHC, (2) values of F calculated to be greater than unity cannot be explained simply by the presence of EHC, (3) calculations of E based on the usual expression F = f*a(1 - E) are erroneous for drugs subject to EHC, and (4) a compound that has a high systemic availability and is subject to EHC is not necessarily inefficiently metabolized. The quantitative interrelationship of systemic availability and its determinants is illustrated using a contour plot. Slices through the surface are used to demonstrate that the presence of EHC changes the sensitivity of F to changes in E.

Animals↗

PubMed1986

Availability of lysine in meat meal, meat and bone meal and blood meal as determined by the slope-ratio assay with growing pigs, rats and chicks and by chemical techniques.

1. The availability of lysine in four meat meals (MMs), four meat and bone meals (MBMs) and two blood meals was determined using the slope-ratio assay with growing pigs, rats and chicks and with two chemical techniques. 2. The availability of lysine (proportion of total) in the eight MMs or MBMs ranged from 0.48 to 0.88 for pigs, from 0.49 to 0.88 for rats and from 0.68 to 0.88 for chicks. There was no apparent relation between the availability estimates for pigs, rats and chicks for the individual meals. 3. For the two blood meals, availability estimates were 1.03 and 1.13 for pigs, 0.81 and 0.80 for rats and 1.07 and 1.02 for chicks. 4. Values for the indirect and direct 1-fluoro-2,4-dinitrobenzene-'available'-lysine assays ranged from 0.77 to 0.88 and 0.78 to 0.93 respectively for the eight MMs and MBMs. There appeared to be no relation between these values and the pig estimates.

Animal Feed↗

PubMed1986

Determination of digestible and available amino acids in meat meal using conventional and caecectomized cockerels or chick growth assays.

1. The present study was designed to compare true digestible amino acid values for meat meal with available amino acid values. True digestible values were determined with a 48 h excreta collection assay using conventional (CONV) and caecectomized (CEC) cockerels. Available values for lysine, methionine and cystine were estimated by chick growth assays. 2. True digestibilities of all sixteen measured amino acids (expressed as a proportion of the total) were lower for CEC than for CONV cockerels, with the average difference being approximately 0.10. 3. Chick growth assays based on total weight gain indicated that the availabilities of amino acids expressed as a proportion of the total amino acids in meat meal were: 0.70 for lysine, 0.75 for methionine and 0.48 for cystine. Partitioning weight gains to reflect only growth attributable to supplemental crystalline amino acid or meat meal intake consistently yielded higher availability values than when total weight gains were used. 4. True digestibility values determined with CEC cockerels were in better agreement with chick available values than were true digestibility values determined with CONV cockerels. 5. The amounts of amino acids present in the caeca of meat meal-fed CONV cockerels at 48 h after feeding were small when compared with those levels voided in the excreta and those levels consumed in the feed. 6. Multiple regression analyses of excreta and caecal amino acid profiles at 12 and 48 h after feeding suggested that significant amounts of non-digested dietary amino acids flowed into the caeca and were subsequently metabolized by the caecal microflora.

Amino Acids↗

PubMed1975

[Determination of metabolic availability of zinc and estimation of zinc requirements through changes in the activity of metallo-zinc enzymes].

Data on the zinc requirements of animals vary widely with the type of diet or kind of zinc compound considered, as they are dependent on the kind of definition and estimation of mineral requirements used which, in turn, are based on the analytical content of the mineral in the diet. Actually, requirements for a particular trace element are the same for any diet provided differences in the rate of absorption and metabolic availability of the element are taken into consideration. A suggestion is made in the present paper to utilize changes in the activity of different metallo-zinc enzymes as a method for determining the degree of metabolic availability of zinc. Within the framework of a repletion trial young male rats were fed a semisynthetic casein diet containing 1.2 ppm of zinc for a 14-day period of zinc depletion followed by a 15-day repletion period during which the rats received a diet containing 4.5 ppm or 12 ppm of zinc. In this trial the pattern of activity of the alkaline phosphatase in serum and in the femoral bones was studied and the level of pancreatic carboxypeptidase A and B was estimated. The data thus obtained were compared with those of pair-fed control animals and control animals fed a libitum. (96 ppm of dietary zinc). The results of the present trial show the metabolic availability of zinc can be determined by measuring the level of activity of these metallo-zinc enzymes. A suitable model was established. Moreover, attempts have been made to show in which way the zinc demands of growing, full-grown, pregnant and lactating animals may be estimated by measuring changes in the degree of activity of these metallo-zinc enzymes. A definition is, in this case, given by that amount of zinc which allows for an optimum activity of the different metallo-zinc enzymes. Such data are applicable only to a particular diet or are valid only for a particular zinc compound. Principally, it is much better to relate the Zn requirements of the animal to the level of absorbable and metabolically available zinc. The present model has been suggested to provide a possibility for measuring the metabolic availability of zinc in the body.

Alkaline Phosphatase↗

PubMed1981

Availability of vitamin B6 and pantothenate in an average American diet in man.

The availability of vitamin B6 and pantothenate in an average American diet was assessed healthy male volunteers. The subjects received two types of diets, both nutritionally equivalent to the average American diet: period 1 (35 days), semipurified formula diet (low in both vitamins) with daily supplements of 1.1 mg pyridoxine and 8.2 mg pantothenate; period 2 (35 days), natural food sources, providing 2.3 mg vitamin B6 and 11.5 mg pantothenate/day; period 3 (21 days), formula diet, providing 2.7 mg pyridoxine and 8.2 mg pantothenate/day. Daily protein intake was 96 g throughout the study. Vitamins in food and urine samples were determined microbiologically and plasma pyridoxal phosphate by a tyrosine apodecarboxylase radioassay method. Compared to the availability of the pure vitamins as 100%, the availability of vitamin B6 ranged from 61 to 81% with a mean of 71% using plasma pyridoxal phosphate data, and ranged from 73 to 92% with a mean of 79% according to urinary vitamin B6 data. Availability of pantothenate ranged from 40 to 61% with a mean of 50%, according to urinary pantothenate data. The average American diet used in our study contained 1.7 and 5.8 mg/day of available vitamin B6 and pantothenate, respectively.

Adult↗

PubMed1979

A rat bioassay for measuring the comparative availability of carbohydrates and its application to legume foods, pure carbohydrates and polyols.

An assay was developed to evaluate the bioavailability of dietary carbohydrate by slope-ratio analysis of weight gain and plasma ketones of rats fed a carbohydrate-free diet supplemented with glucose as a standard and selected food items, pure carbohydrates and polyols. The diet was based on 35% food grade oleic acid, 12% casein protein supplemented with methionine (0.3%) and arginine (0.2%), 7.5% soybean oil, 37% cellulose, minerals and vitamins. Glucose, as the reference standard, or test materials were incorporated in the diet by replacing equi-energetic amounts of oleic acid and adjusting cellulose to equalize total weight. Optimal levels of protein (casein) and triglyceride (soybean oil) in the basal diet were defined as those levels above which additional protein or fat would serve only to provide endogenous glucose from their glucogenic amino acids and glycerol constituents. A standard dose-response curve was obtained by feeding diets containing 0%, 1% and 2% glucose. Similar dose response curves were obtained by feeding test materials. Under these experimental conditions, additional glucose or additional protein were growth stimulating and casein had approximately 50% of the value of an equal weight of glucose, which was consistent with its content of glucogenic amino acids. The specific carbohydrate value of a food was estimated in the assay by subtracting the calculated glucogenic value of its digestible protein from the total response. The apparent availability of the carbohydrates (i.e., nitrogen-free extract) in soybean meal, lima bean (Phaseolus lumatus), and chick pea (Cicer arietinum) were 35, 70, and 80%, respectively, as available as glucose. Galactose, a 1:1 mixture of galactose + glucose, fractose and starch were as available as glucose. Lactose, ribose, sorbitol, and xylitol were 50 to 65% as available as glucose while mannitol and inulin were not available to a significant extent. Possible metabolic bases for these differences are discussed.

Amino Acids↗

PubMed1981

Apparent and true availability of amino acids from common feed ingredients for channel catfish.

The apparent and true amino acid availability values for corn, wheat middlings, rice bran, rice mill feed, soybean meal, peanut meal, cottonseed meal, meat and bone meal, and two different samples of menhaden fish meal were determined in adult channel catfish. Although there was reasonable agreement between protein digestibility values and average amino acid availability values, individual amino acid availabilities were variable within and among the various feed ingredients tested. Therefore, we recommended that amino acid availability values should be used for more accurate catfish feed formulation. In addition, it appears that the use of true amino acid availability values should be used for feed ingredients of relatively low protein content.

Amino Acids↗

PubMed1992

Fluoride availability in human saliva after dentifrice use: correlation with anticaries effects in rats.

Studies were conducted to determine fluoride availability in saliva after dentifrice use and to relate this parameter to cariostatic efficacy in rat caries experiments. Three dentifrices--two commercial formulations (Colgate Winterfresh Gel and Crest Dentifrice with Na-Sr-polyacrylate) and an Experimental dentifrice--were compared with respect to salivary fluoride availability. All of the dentifrices tested contained 1100 ppm F as sodium fluoride. It was observed that the Experimental dentifrice and Crest dentifrice with Sr-polyacrylate exhibited low salivary fluoride availability relative to the Colgate Winterfresh Gel. Salivary fluoride availability was assessed by means of two parameters: (a) the fluoride concentration in the dentifrice saliva slurry expectorated after brushing, and (b) the area under the curve of salivary F concentration vs. time for up to two hours after dentifrice use. In two rat caries experiments, it was observed that both the Experimental dentifrice and the Sr-polyacrylate dentifrice provided less cariostatic efficacy than the clinically validated Positive Control (Colgate Winterfesh Gel). Analysis of these data provides further evidence in support of the concept that fluoride availability in saliva following dentifrice use is an important parameter related to anticaries efficacy.

Acrylic Resins↗

PubMed1985

Biologically available iodine in goitrogenic diets.

Eight different sources of low-iodine diet (LID) were tested in mice over 14 years. The available iodine in each diet was measured by isotopic equilibration. Commercially prepared Remington diets contained 6.8 to 69.3 ng available iodine/g, and the results were usually different from shipment to shipment. Some samples produced greatly enlarged thyroids. The Remington diets from two sources were occasionally low in iodine but produced little thyroid enlargement. Between 1977 and 1980 only one shipment of Remington diet was found to contain less than 10 ng available I/g, and it resulted in large goiters. Since 1980 other compositions of LID have been used, but they caused additional abnormalities during breeding or chronic feeding. A low-iodine wheat diet produced goiter in mice more readily than in rats. In the course of testing for unavailable forms of dietary iodine, it was found that only 34.2% of thyroxine iodine was available to the thyroid iodine pool of mice. It is concluded that unidentified nutritional deficiency or dietary contaminants can alter the goitrogenic response to restricted iodine intake. Furthermore, at least one natural form of potential dietary iodine is incompletely available to mice.

Animals↗

PubMed1984

Available biotin content of various feed ingredients.

The availability to the chick of the microbiologically determined biotin in various feed ingredients was assayed using a standard curve methodology. The chicks were grown up to 28 days of age. Ingredients of the standard diet were partially replaced by the test ingredient. Each test mixture was also supplemented with 200 micrograms biotin/kg and fed to a control group. The percentage of growth of the test chicks compared with the controls proved to be a suitable parameter for the assessment of biotin availability. Availability of biotin was expressed in percentage of the biotin determined microbiologically. In the tested cereals availability was distinctly low, whereas in some other feed ingredients the availability was reduced less.

Animal Feed↗

PubMed1992

Effect of overcooked soybean meal on chicken performance and amino acid availability.

Studies were conducted to evaluate the effect of overcooked soybean meals (SBM) on chick growth and amino acid availability. The SBM were custom-prepared at a commercial processing plant by changing the conditions of a desolventizer-toaster (DT) unit. Six progressively overcooked meals (designated SBM1 to 6 with SBM1 as normal, and SBM6 overcooked) were produced by increasing temperature by up to 50% and extending retention time by up to 75% above normal. The meals measured .05, .03, .01, .09, .00, and .00 delta pH of urease activity; 6.10, 5.01, 4.62, 4.83, 2.32, and 1.78 mg/g SBM of trypsin inhibitor activity; 92, 89, 91, 88, 81, and 81% of protein solubility in .2% KOH; and 46, 43, 41, 40, 23, and 19% of protein solubility in .1 M borate at 40 C, respectively. Glucose content in the hydrolysate of the soluble carbohydrate extract did not differ among the meals, indicating no differences in the degradation of sucrose, raffinose, and stachyose with increasing heat treatment. In a chick growth experiment with a methionine-adequate, low-protein diet, chicks fed SBM1 showed significantly greater weight gain than chicks fed SBM3, 5, or 6. The SBM1, 2, 5, and 6 were chosen for a study of amino acid availability. No differences were observed in amino acid content. There were significant differences in apparent amino acid availability to growing chicks, but not in true amino acid availability by adult roosters among the four meals. The results suggest that the temperature or the retention time of a DT unit may be increased by 50% over the usual operating conditions without reducing amino acid availability from SBM.

Amino Acids↗

PubMedDate not supplied

Available amino acid score for evaluating protein quality of foods.

Amino acid scores corrected for true digestibility of individual amino acids (as determined by rat balance method) were termed "available amino acid scores" in the present investigation. Available amino acid scores were calculated for 7 protein sources and their 10 supplementary or complementary mixtures which have been tested in collaborative amino acid and rat growth assays for evaluating protein quality. The available amino acid scores were as follows: casein + methionine (100); egg white (100); rapeseed protein concentrate, RPC (94); casein (93); beef (89); soya assay protein, SAP (62); pea flour (61); whole wheat flour, WW (38); SAP + methionine (88); pea flour + methionine (72); WW + lysine (67); WW + casein (84); WW + egg white (79); WW + RPC (65); WW + beef (77); WW + SAP (70); and WW + pea flour (75). These scores were similar to the collaborative relative NPR values; the differences were less than 10 units (2-9 units) in most cases. The positive correlation (r = 0.92) between available amino acid scores and relative net protein ratio (RNPR, a rat growth method) values was highly significant (P less than 0.01) and the origin of the regression line (y = 0.92x + 1.88) was not significantly different from zero. Amino acid bioavailability has previously been a problem, preventing widespread acceptance of amino acid score. Available amino acid score solves this problem.

Amino Acids↗