Biomedical subjects

J A Olson

Publications and source records attributed to J A Olson.

At least 127 records · Page 7Linked to original sources

PubMed1990

Vitamin A status in preschool-age Indonesian children as assessed by the modified relative-dose-response assay.

The modified relative-dose-response (MRDR) assay has been validated in rats as a function of vitamin A status and tested in a group of American children. In this study the MRDR assay was applied to West Javan children who are at risk of being vitamin A deficient. Of 86 children enrolled, 75 were tested. In a time-course study involving 22 children aged 3.7-5.3 y, blood samples were taken at different times after doses of 0.35 mumol 3,4-didehydroretinyl acetate/kg body wt. Generally, the ratio of dehydroretinol to retinol (DR-R ratio) peaked between 4 and 8 h. Thereafter, in a survey of 53 children aged 0.6-4.8 y, single blood samples were drawn 5 h after the dehydroretinyl acetate dose. The DR-R ratio ranged from 0.0028 to 0.169. With a DR-R ratio of 0.03 as the cutoff value, 62% of the children were judged to be of marginal vitamin A status.

Anthropometry↗

PubMed1990

In situ enzyme-linked immunosorbent assay to quantitate in vitro development of Eimeria tenella.

An in situ enzyme-linked immunosorbent assay was developed to measure in vitro development of Eimeria tenella. The assay used a polyclonal, anti-merozoite serum produced by immunization with culture-derived, chromatographically purified merozoites. Although this antiserum cross-reacted with sporozoite-infected cultures (by indirect immunofluorescence and in situ enzyme-linked immunosorbent assay), it clearly distinguished the increase in antigen synthesized throughout intracellular growth. The assay can be used for high-throughput, anticoccidial drug screening, for which it gives quantitative results that are comparable to the published radiometric [( 3H]uracil incorporation) endpoint.

Animals↗

PubMed1990

Identification of a novel family of growth hormone-related proteins secreted by rat placenta.

Mid-to-late gestation rat placenta synthesizes a number of proteins related to prolactin, including rat placental lactogen II (rPL-II), rat prolactin-like protein A (rPLP-A) and rat prolactin-like protein B (rPLP-B). This study identifies a new family of proteins synthesized and secreted by gestation day 15 placental explants which exhibit amino acid homology to growth hormone precursors from several species. Placental explant medium was fractionated by ammonium sulfate precipitation and analyzed by two-dimensional SDS-polyacrylamide gel electrophoresis to isolate four distinct proteins with Mr values of 28,000, 23,000, 25,000 and 30,000 and pI values of 5.7, 5.7, 5.4 and 5.3, respectively. These proteins represent a major fraction of secretory proteins with Mr in the 20,000 to 30,000 range. Immunoblot analysis showed that none of the four proteins crossreacted with antipeptide antisera against rPL-II, rPLP-A, or rPLP-B. These proteins were electrophoretically transferred from two-dimensional SDS-polyacrylamide gels onto an Immobilon PVDF membrane and N-terminal amino acid microsequencing carried out with a gas phase sequencer. N-terminal sequences of 45, 37, 37 and 32 amino acid residues were identified for proteins 1, 2, 3 and 4, respectively. The four proteins exhibit 76% to 97% homology. Computer analysis further revealed a 28% identity in a 32 amino acid overlap which begins at residue 14 of the 28,000 Mr protein (protein 1) and at residue 31 of growth hormone precursors of rat, mouse and human. The 32 amino acid overlap is 78% homologous if conservative amino acid replacements are included.

Amino Acid Sequence↗

PubMed1990

Retinyl ester (vitamin A ester) and carotenoid composition in human liver.

Surgical liver biopsy samples from seven diseased and five healthy human subjects, 3-33 years of age, were analyzed by reversed-phase high-pressure liquid chromatography for retinol (vitamin A alcohol), retinyl esters (vitamin A esters), and carotenoids. Total liver vitamin A values ranged from 7.8 to 2860 nmol/g liver (2.2 to 817 micrograms/g). As a percentage, liver retinol decreased with increasing liver reserves of vitamin A. Retinyl palmitate was the predominant vitamin A ester (57 to 83 mole%) in all samples, with retinyl stearate (5.5 to 11.4%), oleate (4.9 to 17.2%), and myristate plus palmitoleate (pair not resolved; 3.3 to 11.9%) next most common. Lesser amounts of retinyl linoleate, linolenate, and arachidonate were found. Normal livers had significant amounts of several carotenoids: lutein (0.2 to 16.2 nmol/g), lycopene (10.2 to 55.1 nmol/g), alpha-carotene (3.0 to 7.3 nmol/g), and beta carotene (5.8 to 25 nmol/g). Total carotenoid values ranged from 26.5 to 67 nmol/g in normal liver samples. There was no correlation between liver vitamin A and individual or total carotenoids in normal livers.

Adolescent↗

PubMed1990

Use of the modified relative dose response (MRDR) assay in rats and its application to humans for the measurement of vitamin A status.

After an appropriate dose of 3,4-didehydroretinol (vitamin A2, DR) is given orally in corn oil to retinol (R)-depleted rats, the ratio of plasma DR/R values at 3.5 h is inversely related to the liver concentration of vitamin A (Tanumihardjo & Olson, 1988). In the present study, a similar procedure, termed the modified relative dose response (MRDR) assay, was employed with rats containing a much broader range of liver reserves; ie, less than 2 to 107 nmol of vitamin A per g wet weight of liver (less than 1 to 30 micrograms/g). The DR/R ratio for 15 of 16 rats with liver reserves less than 17 nmol/g (less than 5 micrograms/g) was greater than 0.15, whereas the ratio was less than 0.15 for 7 of 8 rats with liver reserves greater than 17 nmol/g. This distribution provides sensitivity, specificity and positive predictive values of 94, 88 and 94 per cent, respectively. The DR/R ratios reached a maximal plateau in two other groups of rats between 3.5 and 8 h. At all times up to 24 h, mean DR/R ratios for vitamin A-depleted rats (45 +/- 6 nmoles of vitamin A/g liver) were approximately twice those for vitamin A-sufficient rats (230 +/- 40 nmoles of vitamin A/g liver). In three well-nourished adults, presumably with liver reserves of greater than 300 nmol/g wet weight liver (greater than 80 micrograms retinol equivalents/g), and in two young (1- and 3-years old) well-nourished children, maximal DR/R ratios were less than 0.023. In these cases, peak DR/R ratios were observed, with one possible exception, between 8 and 12 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗

PubMed1989

Chemical synthesis of all-trans-[11-3H]retinoyl beta-glucuronide and its metabolism in rats in vivo.

All-trans-[11-3H]retinoyl beta-glucuronide (RAG) was synthesized in a single step from all-trans-[11-3H]retinoyl fluoride, with a 24% yield. After its intraperitoneal injection into rats, RAG was detected in the blood, liver, intestine and kidney during the following 24 h period. Although the concentration of radiolabelled metabolites decreased with time, RAG predominated at nearly all times in nearly all tissues. Small amounts of retinoic acid (RA) were also universally present, together with unidentified polar metabolites and small amounts of non-polar esters of RA. The major excretion products of RAG in faeces and urine were RA and polar metabolites. Thus RAG, although converted in part to RA in vivo, persists as a major component in blood and tissues for at least 24 h. These observations support the concept that the retinoid beta-glucuronides might serve a physiologically significant role in the function of vitamin A.

Animals↗

PubMed1989

Vitamin A concentrations in liver determined by isotope dilution assay with tetradeuterated vitamin A and by biopsy in generally healthy adult humans.

The vitamin A status in 11 generally healthy surgical patients was estimated by measuring the dilution of a 45-mg oral dose of tetradeuterated retinyl acetate (99% pure). After purification of retinol by high-performance liquid chromatography, the ratio of 2H4-retinol:1H-retinol in plasma was measured by gas chromatography-mass spectrometry. On the basis of the observed ratios of [2H4]retinol:[1H]retinol over 19-47 d, the total body reserves and liver concentrations of vitamin A were calculated. Liver biopsy samples taken at surgery were directly analyzed for vitamin A. The correlation coefficient between calculated and measured liver vitamin A concentrations for 10 of the subjects was 0.88, and the Spearman's rank correlation coefficient was 0.95 (p less than 0.002). Thus, total body reserves of vitamin A in humans can be estimated validly in the marginal and satisfactory ranges by a benign, relatively noninvasive procedure.

Adult↗

PubMed1989

Characterization of retinyl beta-glucuronide in human blood.

Retinyl beta-glucuronide has been identified as a normal endogenous component of human blood, as have retinoyl beta-glucuronide and retinoic acid. The mean serum concentration of retinyl beta-glucuronide in adult volunteers (n = 6) was 6.8 +/- 4.0 nmol/L (means +/- SD) with a range from 1 to 11 nmol/L. Purified serum retinyl beta-glucuronide was characterized by the mass spectrum of its methylated trimethylsilyl derivative, by its hydrolysis by beta-glucuronidase, and by its chromatographic behavior in high-performance liquid chromatography systems. During a single day, concentrations of retinyl beta-glucuronide, retinoyl beta-glucuronide, and retinoic acid varied approximately two-fold.

Adult↗

PubMed1989

Provitamin A function of carotenoids: the conversion of beta-carotene into vitamin A.

Two pathways have been suggested for the conversion of carotenoids to vitamin A in mammals, central cleavage and excentric cleavage. An enzyme, beta-carotenoid-15,15'-dioxygenase (EC 1.13.11.21), has been partly purified from the intestines of several species and has been identified in several other organs and species. The enzyme, which converts beta-carotene into two molecules of retinal in good yield, requires molecular oxygen and is inhibited by sulfhydryl-binding and iron-binding reagents. Most provitamin A carotenoids, including the beta-apo-carotenals, are cleaved to retinal by this enzyme. Its maximal activity in the rabbit is approximately 200 times that required to meet nutritional needs but is less than 50% of that expected to produce signs of vitamin A toxicity. Excentric cleavage unquestionably occurs in plants and some microorganisms and might occur in mammals. Thus far, however, carotenoid dioxygenase with excentric bond specificity has been identified in mammals, the yield of beta-apo-carotenals from beta-carotene in vivo and in vitro is very low, and beta-apo-carotenals are formed nonbiologically from beta-carotene. To remain viable as an alternative pathway of vitamin A formation from carotenoids in mammals, the excentric cleavage hypothesis clearly requires unambiguous direct supporting evidence.

Animals↗

PubMed1989

Biological actions of carotenoids.

Of approximately 600 naturally occurring characterized carotenoids, fewer than 10% serve as precursors of vitamin A in mammals. Apart from vitamin A formation, carotenoids show unique physicochemical properties and interesting biological effects. The inverse association between the ingestion of carotenoid-containing fruits and vegetables and the risk of certain forms of cancer has attracted significant attention. In considering the effects of carotenoids in mammals, a distinction should clearly be made among functions, actions and associations. Furthermore, carotenoids might well be classified in relation to defined biological actions, and not just in relation to nutritional activity.

Animals↗

PubMed1989

Upper limits of vitamin A in infant formulas, with some comments on vitamin K.

Current Food and Drug Administration (FDA)-approved levels of adequacy and of upper limits in infant formulas for vitamin A are 250 and 750 IU per 100 kcal, respectively. The level of adequacy is generous relative to need. Because vitamin A toxicity has been noted in infants at intakes of 2,100 IU per 100 kcal, an upper limit might well be selected in the range of 750-1,000 IU per 100 kcal for healthy infants. Some children and adults, however, are intolerant of relatively low intakes. The current FDA-approved adequacy level for vitamin K is 4 micrograms per 100 kcal, which also is generous relative to need. An upper limit has not previously been set. Neither single intramuscular doses of phylloquinone that are 100 times the RDA (RDI) for infants nor diets that contain 10-20 times the RDA (RDI) for adults show any adverse effects. Some allergic reactions to injected vitamin K have been reported, however, and menadione, even in low doses, shows significant toxicity in neonates. Thus, although toxicity to phylloquinone is unlikely, it has been suggested that the upper limit of phylloquinone in infant formulas be set at 20 micrograms per 100 kcal, primarily to discourage nutritionally unwarranted supplementation.

Female↗

PubMed1989

The effect of dietary fatty acid composition on liver retinyl ester (vitamin A ester) composition in the rat.

The dependence of liver retinyl ester (vitamin A ester) composition on dietary fatty acid composition was studied in rats. Weanling male Sprague-Dawley rats were fed purified test diets containing 8% of one of 10 test triglycerides (either tributyrin, tricaproin, tricaprylin, tricaprin, trilaurin, trimyristin, tripalmitin, tristearin, triolein, trilinolein) or corn oil (a mixed triglyceride) for 23 d after an initial 1-wk stabilization period. Essential fatty acids were provided by safflower oil (8 g/kg diet). Total liver fatty acid composition showed the expected responses to dietary fatty acid intake; short-chain and medium-chain fatty acids were readily elongated to palmitate and stearate, and palmitate and stearate were readily desaturated. Consumption of oleate or linoleate (as their triglycerides) markedly enriched their concentrations in liver lipids. The proportions of palmitate were generally greater in liver retinyl esters than in total liver fatty acids, and the proportions of oleate were less. However, retinyl ester composition was significantly affected by dietary triglyceride, particularly by diets providing long-chain fatty acids. Total liver vitamin A levels were depressed in the group fed trilinolein.

Animals↗

PubMed1989

Biological actions of carotenoids.

Of 600 carotenoids from natural sources that have been characterized, fewer than 10% serve as precursors of vitamin A. Many dietary carotenoids, both with and without provitamin A activity, are found in the blood and tissues of humans. beta-Carotene, the most nutritionally active carotenoid, comprises 15-30% of total serum carotenoids. Vitamin A is formed primarily by the oxygen-dependent central cleavage of beta-carotene and other provitamin A carotenoids. Several carotenoids show enhancement of the immune response, inhibition of mutagenesis, reduction of induced nuclear damage, and protection from various neoplastic events in cells, tissues, and whole animals. Carotenoids also protect against photo-induced tissue damage. Some carotenoids, including beta-carotene, quench highly reactive singlet oxygen under certain conditions and can block free radical-mediated reactions. In epidemiological studies, the intake of carotenoid-rich fruits and vegetables has been correlated with protection from some forms of cancer, particularly lung cancer. Similarly, serum beta-carotene levels have been associated with a decreased chance of developing lung cancer. It must be stressed, however, that these epidemiological associations do not show cause and effect. In this regard, long-term intervention trials with beta-carotene supplements are in progress. Whatever the results of these trials, carotenoids clearly show biological actions in animals distinct from their function as precursors of vitamin A.

Animals↗

PubMed1988

13-cis-retinoic acid stimulates in vitro mannose 6-phosphate hydrolysis and inhibits retinol esterification and benzo[a]pyrene hydroxylation by rat-liver microsomes.

13-cis-Retinoic acid, a drug used at high doses in the treatment of recalcitrant acne, increased the permeability of rat-liver microsomal membranes to mannose 6-phosphate in vitro, as indicated by an increase in mannose-6-phosphatase activity. At the same concentrations, four other amphiphiles, including all-trans-retinoic acid, were much less effective. 13-cis-Retinoic acid also inhibited retinol esterification and benzo[a]pyrene hydroxylation in microsome preparations in vitro. Although the molecular mechanism and the reversibility of these effects have not yet been studied, the interaction of 13-cis-retinoic acid with cell membranes may well be involved in both its therapeutic and toxic manifestations.

Animals↗

PubMed1988

Synthesis and metabolism of all-trans-[11-3H]retinyl beta-glucuronide in rats in vivo.

All-trans-[11-3H]retinyl beta-glucuronide (all-trans-[11-3H]ROG) was synthesized from [3H]retinol by an improved synthetic procedure. After its intraperitoneal injection into rats, ROG is initially found as the predominant labelled component in the serum, but then is distributed to the liver, intestine, kidney and other organs of the body. Esters of vitamin A, which constituted the major metabolite of ROG, were detected in the liver as well as in other tissues. Of the labelled vitamin A esters derived from tritiated ROG in the liver and intestine, about 50% contained 5,6-epoxyretinol, which was characterized by its chromatographic behaviour, formation of an acetyl ester and lack of reactivity with diazomethane. Thus ROG, although converted to retinol in vivo, might also act physiologically in an intact form.

Animals↗

PubMed1988

Rapid, simultaneous determination of isomers of retinal, retinal oxime and retinol by high-performance liquid chromatography.

Thirteen geometric isomers of retinol, retinal and retinal oxime were resolved in a single chromatographic run on two 250 X 4 mm 5-micron LiChrosorb Si 60 columns in series, using 11.2% ethyl acetate, 1.4% 1-octanol and 2% dioxane in hexane as the mobile phase. All the 11-cis and all-trans isomers of retinol and retinal oxime were completely resolved from each other and from the 9-cis and 13-cis isomers. This chromatographic procedure should be particularly useful for quantifying geometric isomers of retinoids in methylene chloride-hydroxylamine extracts of biological samples such as ocular tissues.

Animals↗

PubMed1988

Hydrolysis of cis and trans isomers of retinyl palmitate by retinyl ester hydrolase of pig liver.

Relative retinyl ester hydrolase activities of pig liver homogenates (n = 4) toward 9,13-cis-, 13-cis-, 9-cis-, and all-trans-retinyl palmitate were 6.8 +/- 0.5 (SE), 5.7 +/- 0.5, 2.4 +/- 0.1, and 1, respectively. The range of apparent Km values for the four isomers was 142 to 268 microM, and the pH optima were 8-9 in all cases. Peak activities of retinyl ester hydrolase activities in pig liver cytosol toward 13-cis- and all-trans-retinyl palmitate were found in the 20 to 40% and in the 60 to 80% saturated ammonium sulfate (AS) fractions, respectively. By use of size-exclusion chromatography in 2 M KCl, hydrolase activity eluted at volumes corresponding to greater than 2000, 180, and 15 kDa from the 20-40% AS fraction, and at 180 kDa from the 60-80% AS fraction. On the basis of molecular size, different substrate specificities, detergent effects, and susceptibilities to inhibition by phenylmethylsulfonyl fluoride, we conclude that at least three distinct retinyl ester hydrolases are present in pig liver cytosol.

Ammonium Sulfate↗

PubMed1988

A direct microassay for serum retinol (vitamin A alcohol) by using size-exclusion high-pressure liquid chromatography with fluorescence detection.

Serum retinol (bound to plasma retinol-binding protein, RBP) can be determined by direct injection of as little as 20 microliter of serum or plasma by using size-exclusion high-pressure liquid chromatography (SE-HPLC) with fluorescence detection. Toyo Soda TSK G-3000SW columns (0.75 X 7.5-cm guard column plus 0.75 X 30-cm analytical column) were eluted with 0.2 M NaCl/0.01 M phosphate buffer (pH 6.8) at 1 ml/min, with detection at 280 nm for protein elution. Fluorescence of the retinol-RBP complex was monitored with excitation at 334 nm (interference filter) and emission at 425 nm (long-pass filter). The retinol-RBP complex eluted as two peaks, the holo-RBP-transthyretin complex (apparent molecular weight 70,000) and holo-RBP (apparent molecular weight 9000). Identities of these peaks were established by immunodiffusion assay of the proteins and by extraction and analysis of retinol. Nonideal interactions with the column packing seem to be responsible for the low apparent molecular weight of holo-RBP. The first peak predominated when large volumes of serum (100 to 250 microliters) were injected, and the second when small volumes (5 to 50 microliters) were analyzed. The integrated area of the two fluorescence peaks due to retinol bound to RBP was proportional to the volume of a serum sample injected over the range 5 to 250 microliters.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗