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Biomedical subjects

G P Tryfiates

Publications and source records attributed to G P Tryfiates.

At least 19 recordsLinked to original sources
PubMed1996

Vitamin B6 and cancer: synthesis and occurrence of adenosine-N6-diethylthioether-N-pyridoximine-5'-phosphate, a circulating human tumor marker.

In the course of studies aimed at deciphering the metabolic transformations of [3,4-14C] and [3H]C6-pyridoxine hydrochloride by tumor-bearing rats and tumor cells in culture, biosynthesis of a novel labeled product was observed. Its production began with the onset of tumor growth and increased as cell proliferation increased. Chemical, enzymatic, precursor labeling, and analytical tests on the isolated product indicated this product as adenosine-N6-diethylthioether-N-pyridoximine-5'-phosphate (compound 1). In confirmation, the chemical synthesis and characterization of compound 1 are presented in this study. In addition, blood samples from 28 normal subjects, 28 cancer patients with different malignancies, and 39 patients with a variety of other than cancer ailments were screened for compound 1 on a blind basis using reverse phase ion-paired high-performance liquid chromatography. The results show that the level of the vitamin B6 conjugate in the circulation of control subjects, cancer patients in remission, and patients with other diseases was only minimal. Cancer patients with active disease had 3-4-fold higher levels (P < 0.00001). Our results also confirm previous findings regarding the structure of compound 1 and show its potential value as a circulating human tumor marker that could be successfully used for cancer detection.

Adenosine↗
PubMed1989

Biosynthesis of a novel form of vitamin B-6 by tumor cells.

Studies on the time-course utilization of radiolabeled pyridoxine in hepatoma-bearing rats led to the discovery of a novel vitamin B-6 product. It is present in a spectrum of tumor lines, but it is absent or occurs minimally in normal tissues. Hepatomas incorporate up to 20-30% of labeled pyridoxine into the novel species. Its structure was tentatively identified as adenosine-N6-methyl, propylthioether-N-pyridoximine-5'-phosphate. In the present study, 3B3 mouse-human hybridoma cells were incubated with radiolabeled precursor molecules, perchloric acid cell extracts were analyzed by high performance liquid chromatography (HPLC), and radioactivity in effluent fractions was measured. The results show that [G-3H]pyridoxine, [2,8-3H]adenosine, L-[35S]cysteine and L-[U-14C]serine are incorporated into the novel tumor product. These findings are interpreted to indicate that the correct structure of the novel product is adenosine-N6-diethylthioether-N'-pyridoximine-5'-phosphate. Further, these data demonstrate that tumor cells have evolved novel enzymatic steps for metabolism of vitamin B-6. The potential use of the novel metabolite as a marker for tumor genesis and establishment is especially significant, as the compound is peculiar to the neoplastic state.

Adenosine↗
PubMed1981

Effects of pyridoxine on serum protein expression in hepatoma-bearing rats.

The effect of pyridoxine depletion on the expression of serum protein species in control and Morris hepatoma No. 7777-bearing rats was studied with polyacrylamide gel electrophoresis (PAGE). A group of 20 Buffalo female rats was fed ad libitum a complete diet lacking pyridoxine, whereas a similar group was fed the same diet with pyridoxine. After a 22-day feeding period, 12 animals from each group were inoculated with hepatoma No. 7777 cells in the thigh muscles of both hind legs and allowed to grow for 25 days. Sera were obtained from all animals by heart puncture under light ether anesthesia, and protein species were resolved by PAGE. Eight and four protein bands in the haptoglobin and postalbumin regions, respectively, were resolved from control rat serum, whereas sera from depleted animals had eight and three bands, respectively. Protein expression was facilitated by the presence of hepatomas. Ten and six protein bands were seen in the haptoglobin and postalbumin regions, respectively, upon PAGE of sera from control tumor-bearing rats. A positive synergistic effect between pyridoxine lack and tumor presence was also found. Twelve and five bands were resolved in the haptoglobin and postalbumin regions, respectively, when sera from pyridoxine-depleted tumor-bearing rats were electrophoresed. These results showed that vitamin B6, in addition to its well-known coenzymatic function, exercised a type of control over protein expression, which may be positive or negative depending on the nutritional and health status of the animal.

Animals↗
PubMed1981

Vitamin B6 and cancer (review).

Vitamin B6 is required for normal growth and development, in general. The effect(s) of the vitamin on tumor growth, particularly of Morris hepatomas, and on metabolic function (i.e. enzyme activity) are herewith reviewed. Evidence is presented on the biochemical relationship(s) of pyridoxal 5'-phosphate with thymidylate synthetase and its inactivation by fluorodeoxyuridylate as well as of the therapeutic effects of direct treatment in situ with the antivitamin complexing agent L-penicillamine.

Animals↗
PubMed1981

Control of tumor growth by pyridoxine restriction or treatment with an antivitamin agent.

The growth of 9A and 7316A Morris hepatomas was studied in pyridoxine (PN)-depleted and in pair-fed control Buffalo rats. Rat groups were fed the respective diets for 3 weeks, inoculated with 9A and 7316A tumor cells in both hind leg muscles, and killed after 21 and 41 days respectively. Another group was fed ad lib the PN-sufficient diet and similarly inoculated with 7777 hepatoma cells. In this instance tumors were let grow maximally to the extent that rats were practically unable to move and feed themselves. At this time ten animals were treated with L-penicillamine every other day for 9 days, leaving five (untreated) rats as controls. Rats pair-fed the PN-sufficient diet developed significantly heavier 9A and 7316A hepatomas with P less than or equal to 0.005 and P less than 0.001 significance levels, respectively. Treatment with the antivitamin agent extended significantly animal life span. Six rats lived for 8 days, three for 12, and one for 18 days. Four of the untreated rats died within 3 days, the fifth on the 8th day. These results demonstrate that PN restriction causes significant reduction in tumor weight and its in situ inactivation in vivo significantly extends the life of the tumor bearing animals.

Animals↗
PubMed1980

Activation and protection from 5-fluorodeoxyuridylate inactivation of mammalian thymidylate synthetase by pyridoxal 5'-phosphate.

Rat liver thymidylate synthetase was partially purified by a combination of (NH4)2SO4 precipitation and Sephadex chromatography. Incubation of these partially purified enzyme preparations with pyridoxal phosphate resulted in as much as a 12-fold increase in enzyme activity. In addition, incubation of partially purified thymidylate synthetase preparations with 5.0 X 10(-5) M pyridoxal phosphate protected the enzyme from 5-fluorodeoxyuridylate inhibition to the extent that 78% of the control activity was retained at 5-fluorodeoxyuridylate concentrations as high as 5.0 X 10(-5) M. These findings are discussed in terms of the reported inhibition of tumour growth in the absence of dietary vitamin B6.

Animals↗
PubMed1978

Expression of hormonally induced tyrosine aminotransferase in host liver and Morris hepatoma No. 7777 during cofactor depletion.

Cytoplasmic tyrosine aminotransferase (L-tyrosine: 2-oxoglutarate aminotransferase, EC2.6.1.5) was partially purified from host liver and Morris hepatoma No. 7777 grown in pyridoxine depleted rats. The animals were sacrificed six hours following the intraperitoneal administration of hydrocortisone hemisuccinate. Enzyme preparations were subsequently resolved by electrophoresis on polyacrylamide gels. Enzyme activity was detected histochemically in situ on the gels. Six and at least three enzymatically active protein peaks were detected in host liver and the hepatoma, respectively, by this method.

Animals↗
PubMed1977

Effect of cofactor depletion on liver tyrosine aminotransferase expression.

Hepatic tyrosine aminotransferase (L-tyrosine: 2-oxoglutarate aminotransferase, EC 2.6.1.5) was partially purified from pyridoxine depleted and control rats and subsequently resolved by electrophoresis on polyacrylamide gels. Enzyme activity was detected histochemically in situ on the gel. Six enzymatically active forms were detected. Cofactor depletion effected further resolution of the enzyme into seven active forms as revealed by the bifurcation of the major active peak.

Animals↗
PubMed1976

Metabolism of pyridoxine in the liver of vitamin B-6-deficient rats.

The metabolism of [6-3H]pyridoxine - HCl was investigated in the liver of vitamin B-6-deficient rats. Rats were made vitamin B-6 deficient by feeding ad libitum for 42 days a diet lacking pyridoxine but otherwise optimal. Animals were each injected intraperitoneally with 33 muCi of [6-3H] pyridoxine - HCl and killed at different time intervals afterwards up to 7 days. Radioactively labeled hepatic B-6 compounds were extracted with acid and chromatographically separated on Dowex-X8 (H+) columns and the percent radioactivity for each vitamin compound was then calculated. Maximal uptake in control and deficient animals was observed 30 and 60 min, respectively, after administration of label. Radioactivity was not retained by the control animals but decreased steadily in a linear fashion after 30 min, reaching a low level after 3 h. On the other hand, vitamin deficient animals accumulated almost twice as much radioactivity in their liver as the controls and retained it through 7 days. In vitamin B-6 deficient animals 93% of the injected radioactivity was metabolized within 2 min at which time pyridoxine 5'-P and pyridoxal 5'-P reached 36 and 44% levels, respectively. Pyridoxine 5'-P dropped to minimal values (3%) within 15 min and remained unchanged for 7 days while pyridoxal 5'-P reached a peak (79%) level at 15 min and then began to drop linearly reaching a plateau (29%) at 5 days. Further, as the level of pyridoxal 5-P was falling, pyridoxamine 5'-P was linearly synthesized reaching a platuau low level (3%). The specific activity level of pyridoxal kinase decreased 3.2 times and that of pyridoxine 5'-phosphate oxidase increased 1.5 times in the state of deficiency. The results presented show that metabolism of [3H]pyridoxine in deficiency is characterized by (a) a delayed, two-fold increase in label uptake as well as an extended label retention period, (b) a rapid pyridoxal 5'-P synthesis, and (c) a continuous synthesis (and accumulation) of pyridoxamine 5'-P which is not utilized or further metabolized.

Aging↗
PubMed1976

Effect of pyridoxine on the growth of Morris hepatoma No. 7288Ctc and enzyme activity.

The effect(s) of lack of dietary pyridoxine (PX) on the growth of Morris hepatoma no. 7288Ctc was studied. Buffalo strain female rats were fed a diet lacking PX. Pair-fed controls were fed the same diet with PX added. Animals were inoculated with no. 7288Ctc hepatoma cells at 21 days and were sacrificed 16 days later. Host livers and tumors were removed, weights recorded and the activity of tyrosine aminotransferase (TAT; L-tyrosine: 2-oxoglutarate aminotransferase, EC 2.6.1.5) was determined in both host liver and hepatoma. The average weight of 30 hepatomas grown in pair-fed control rats was 11.61 +/- 1.5 g while the average weight of the same number of hepatomas grown in animals fed the PX free diet was 4.73 +/- 0.7 g (P less than 0.001). Further TAT specific activity levels were 39% and 32% higher in host livers and tumors from deficient animals, respectively. The results show that availability of dietary pyridoxine stimulates the growth of this hepatoma and, in addition, exercises a type of control over the expression of TAT activity.

Animals↗
PubMed1976

Expression of hormonally induced tyrosine transaminase in normal, host liver and three Morris hepatomas.

Cytoplasmic tyrosine transaminase (L-tyrosine: 2-oxoglutarate aminotransferase, EC 2.6.1.5) was partially purified from normal, host liver and three Morris hepatomas and subsequently resolved by electrophoresis on polyacrylamide gels. Enzyme activity was detected histochemically in situ on the gels. Seven enzymatically active forms were detected in normal liver. The presence of growing hepatomas altered significantly the expression of this enzyme. Only one, two and four activity peaks were detected in the host liver of animals with highly (most liver-like), well and poorly (least liver-like) differentiated hepatomas, respectively. Similarly, only one, four and six peaks were detected, respectively, in highly, well and poor differentiated hepatomas.

Animals↗
PubMed1975

The effect of retinol and retinoic acid on physiological and biochemical changes in retinol-deficient rats.

1. The effects of retinol and retinoic acid supplementation of retinol-deficient rats were studied for a variety of metabolic processes shown to be affected by retinol-deficiency. 2. Retinol-deficient rats were found to have decreased body-weight, liver and testes weights, a degeneration of testicular germinal cells, an increased incorporation of labelled choline into liver and testes phospholipids, an increased protein synthetic activity (in vitro) of liver ribosomes, an increased transfer-RNA methyltransferase activity in liver and a decreased activity in testes, an increased DNA content of testicular nuclei, and a decreased uptake of [3-H]thymidine by testicular nuclear DNA. 3. In retinol-deficient rats supplemented for 8 weeks with retinol these changes were reversed, measurements returning to control levels. 4. In retinol-deficient rats supplemented for 8 weeks with retinoic acid all changes were reversed except those in the testes. 5. Testicular signs of retinol deficiency appeared to be delayed when retinoic acid was added to the retinol-deficient diet of weanling rats. This suggests a sparing action of retinoic acid on the rat's utilization of retinol. 6. Suggestions are offered as to why retinoic acid will support growth and development but not spermatogenesis in the rat.

Animals↗