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At least 1,099 records · Page 61Linked to original sources
PubMed1984

Beta-hydroxyaspartic acid in vitamin K-dependent plasma proteins from scorbutic and warfarin-treated guinea pigs.

beta- Hydroxyaspartic acid is a rare amino acid, present in all vitamin K-dependent plasma proteins except prothrombin, and is formed by a post-translational hydroxylation of aspartic acid. We have now investigated whether this hydroxylation, like that of proline in collagen, is vitamin C-dependent. The vitamin K-dependent plasma proteins were isolated from normal and scorbutic guinea pig plasma by barium citrate adsorption and the beta- hydroxyaspartic acid content was determined. Compared with normal animals, scorbutic animals showed no significant reduction of beta- hydroxyaspartic acid content. In warfarin-treated animals there was a decreased content of both beta- hydroxyaspartic acid and gamma-carboxyglutamic acid in the barium citrate adsorbed fraction. It was concluded that the post-translational hydroxylation of aspartic acid is unlikely to be vitamin C-dependent.

1-Carboxyglutamic Acid↗
PubMed1977

Some current aspects of environmental fluoride.

This review presents a Total Environment evaluation of current inorganic fluoride intake by human populations. Inorganic fluoride is a persistant bioaccumulator, and the ever-increasing use (and release) of fluoride compounds in the environment should be of long-term concern in population sub-groups who are most susceptible, and therefore, most "at risk". One of these sub-groups consists of people with impaired kidney function, including subjects with nephorphatic diabetes. The diabetes factor is of particular relevance, not only because the incidence of diabetes has increased by 6%/yr during the period 1965-1975, but also because subjects with nephropathic diabetes can exhibit a polydipsia-polyurea syndrome that results in increased intake of fluoride, along with greater-than-normal retention of a given fluoride dosage. People with inadequate dietary intakes (particularly of Ca and/or Vitamin C) are also likely to be more "at risk" as a consequence of low-dose long-term fluoride ingestion. Evidence is presented, showing that there has been an escalation in dialy fluoride intake via the total human food-and-beverage chain, with the likelihood that this escalation will continue in the future. Recent observations, relating to an increasing incidence of chronic fluoride intoxication among humans, is also emphasized.

Ascorbic Acid Deficiency↗
PubMed1979

Differential regulation of the formation of prostaglandins and related substances from arachidonic acid and from dihomogammalinolenic acid. II. Effects of vitamin C.

Vitamin C over the concentration range 10 to 100 microgram/ml (5.7-57 x 10-5 M) caused a dose dependent and highly significant enhancement of conversion of 14C-dihomogammalinolenic acid (DGLA) to prostaglandin (PG) E1 and to thromboxane (Tx) B1 by human platelets. Vitamin C had no effect on conversion of 14C-arachidonic acid to PGE2 and TxB2. The concentration range is relevant to physiology: in some cells which concentrate the vitamin, such as polymorphonbuclear leucocytes and the adrenal cortex, vitamin C concentrations may be substantially higher than 100 microgram/ml. Vitamin C can therefore selectively enhance the formation of cyclo-oxygenase generated products from DGLA without changing formation of those from AA. This effect can account for a number of the known actions of vitamin C including its effect on the immune system. The implications of this finding are discussed.

8,11,14-Eicosatrienoic Acid↗
PubMed1983

A relationship between ascorbic acid and threonic acid in guinea-pigs.

Threonic acid is a major breakdown product of ascorbic acid used as a food additive. When administered orally to guinea-pigs (100 mg/kg body weight) for periods of 4 or 28 days, it produced a significant fall in the ascorbic acid concentration of certain organs but was without effect on other physiological and biochemical characteristics. The lifespan of scorbutic guinea-pigs was significantly reduced by dietary threonic acid (100 mg/kg body weight). The results indicate that threonic acid may modify the metabolism of ascorbic acid in guinea-pigs.

Animals↗
PubMed1992

Studies on endogenous formation of N-nitroso compounds in the guinea pig supplemented with proline or thioproline and sodium nitrate.

The endogenous formation of N-nitrosoproline (NPRO) and N-nitrosothioproline (NTPRO, N-nitrosothiazolidine-4-carboxylic acid) was studied by monitoring their excretion in the urine of guinea pigs given oral doses of 10 mg proline or thioproline after supplementation with 34 mg (0.4 mmol) sodium nitrate. In order to estimate the conversion of nitrate to nitrite, the animals were also supplemented with 3.5 mg (0.05 mmol) sodium nitrite instead of sodium nitrate. In animals fed commercial diets, the excretion of NPRO and NTPRO under supplementation with sodium nitrate was 2.0 micrograms and 28.7 micrograms/animal/day, respectively, whereas the excretion under supplementation with sodium nitrite was 0.7 micrograms and 13.3 micrograms/animal/day, respectively. The higher excretion of NTPRO than NPRO in each case shows that thioproline is more effective for nitrite trapping than proline. The animals supplemented with nitrate excreted more than twice the amounts of NPRO or NTPRO than those supplemented with nitrite. It is assumed, therefore, that more than 0.1 mmol nitrate is reduced to nitrite and takes part in the endogenous nitrosation of the guinea pig. When various concentrations of L-ascorbic acid (AsA), known to inhibit the formation of N-nitroso compounds, were also administered orally to animals immediately after supplementation with sodium nitrate, the NPRO excretion decreased with increasing AsA concentration. These data indicate that the guinea pig, which is unable to synthesize AsA as well as humans, may be an appropriate animal model for evaluation of the endogenous nitrosation ability of humans ingesting nitrate.

Animals↗
PubMed1988

Assessment of L-ascorbic acid requirement for prolonged survival in ODS rats and their susceptibility to urinary bladder carcinogenesis by N-butyl-N-(4-hydroxybutyl)nitrosamine.

Assessment of L-ascorbic acid requirement for prolonged survival in ODS (genotype: od/od) rats and their susceptibility to urinary bladder carcinogenesis by N-butyl-N-(4-hydroxybutyl)-nitrosamine (BBN) were examined. In ODS rats without L-ascorbic acid synthesizing ability, the 50 ppm dietary total ascorbic acid (TAA) was insufficient to survive for 4 weeks, the 250 ppm dietary TAA was sufficient to survive for 36 weeks. In examination of BBN treatment, ODS rats--although showing a lower availability of TAA than the heterozygotes (+/od) and normal (+/+) rats with L-ascorbic acid synthesizing ability--were equally susceptible to bladder carcinogenesis.

Animals↗