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Biomedical subjects

S Sassa

Publications and source records attributed to S Sassa.

At least 127 records · Page 7Linked to original sources
PubMed1988

Four species of cDNAs for cytochrome P450 isozymes immunorelated to P450C-M/F encode for members of P450IID subfamily, increasing the number of members within the subfamily.

A chicken antibody mono-specific to cytochrome P450C-M/F, which exists in untreated male and female rat liver and catalyses the 2- and 16 alpha-hydroxylation of estrogens (1), was used to screen a cDNA library of male Sprague-Dawley rat liver. Four cDNA clones which encoded P450 isozymes, CMF1a, CMF1b, CMF2 and CMF3, were isolated. CMF1a and CMF2 deduced consisted of 504 and 500 amino acid residues, respectively, while C-terminal 487 and 324 residues for CMF1b and CMF3, respectively, were deduced from the 5'-truncated cDNAs. The isozymes were more than 72% similar in amino acid sequences to each other and to rat P450db1, P450db2 (2), and to a mouse male specific C-P45016 alpha (3), suggesting that they belonged to a new P450 subfamily, P450IID. CMF1a and db1, and CMF2 and db2, respectively, were 99.2% and 99.0% similar in amino acid sequences, suggesting that they were virtually identical. CMF1a and CMF1b were different but 96.1% similar, and CMF3 was between 76% and 78% similar to other members of the rat P450IID family.

Amino Acid Sequence↗
PubMed1988

Regulation of 5-aminolevulinate synthase in mouse erythroleukemic cells is different from that in liver.

We have measured the transcriptional gene activity of 5-aminolevulinate synthase, the first enzyme of the heme biosynthetic pathway, together with corresponding mRNA and protein levels in mouse erythroleukemic cells induced to differentiate with dimethyl sulfoxide. When the heme biosynthetic pathway was blocked by succinylacetone there was a large increase in both 5-aminolevulinate synthase activity and protein levels, and this was reversed by the addition of exogenous hemin. Transcriptional activity of the 5-aminolevulinate synthase gene and mRNA levels were both significantly increased during differentiation of cells by dimethyl sulfoxide but were not markedly altered by succinylacetone or hemin treatment. The results demonstrate that levels of 5-aminolevulinate synthase in mouse erythroleukemic cells are regulated by a significant post-transcriptional mechanism possibly at the translational level. Evidence is also presented for a less significant post-transcriptional control by heme of mRNA levels for 5-aminolevulinate synthase. These results indicate that the regulation of 5-aminolevulinate synthase in differentiating erythroid cells is complex but differs from that in liver cells where heme controls the level of 5-aminolevulinate synthase by acting primarily to inhibit gene transcription.

5-Aminolevulinate Synthetase↗
PubMed1988

Effects of dimethyl sulphoxide on the synthesis of plasma proteins in the human hepatoma HepG2. Induction of an acute-phase-like reaction.

Effects of dimethyl sulphoxide (Me2SO) on the synthesis of plasma proteins by the human hepatoma cell line HepG2 were examined. Me2SO treatment resulted in decreased synthesis of albumin and alpha-fetoprotein, and in increased synthesis of haptoglobin. Plasma-protein profiles induced by Me2SO treatment were very similar to those seen in acute-phase reactions.

Acute-Phase Reaction↗
PubMed1988

Regulation of heme synthesis in HepG2 human hepatoma cells by dimethyl sulfoxide.

Dimethyl sulfoxide (DMSO) treatment of human HepG2 hepatoma cells increases the activity and the concentration of delta-aminolevulinic acid dehydratase (ALAD) to a comparable degree. Results of experiments with transcriptional inhibitors suggest that the increase in ALAD reflects de novo synthesis of the enzyme resulting from transcriptional activation. Commitment to increased ALAD activity in HepG2 cells is seen after 18 hr and complete by 48 hr. In contrast to the effects on ALAD, DMSO decreases the activities of porphobilinogen deaminase and uroporphyrinogen decarboxylase.

5-Aminolevulinate Synthetase↗
PubMed1988

Immunochemical detection of cytochrome P450C-M/F and NADPH-cytochrome P450 reductase in rat liver and kidney.

The localization and distribution of NADPH-cytochrome P450 reductase and cytochrome P450C-M/F were investigated immunohistochemically in the liver and the kidney of untreated rats employing both an unlabelled antibody peroxidase-antiperoxidase method and a peroxidase labelled primary antibody technique. In both immunohistochemical procedures, the reductase and P450C-M/F were detected in hepatocytes throughout the liver. In contrast, the reductase and P450C-M/F in the kidney were only detectable in the proximal tubule cells.

Animals↗
PubMed1988

Tin-protoporphyrin inhibits heme oxygenase and prevents the decline in hepatic heme and cytochrome P-450 contents produced in nude mice by tumor transplantation.

Heme and hemeprotein perturbations are present in nude mice bearing transplanted tumors. Hepatic microsomal heme oxygenase activity is increased 50-100% in tumor bearing nu/nu mice when compared with normal controls. This elevation in activity of the rate-limiting enzyme of heme degradation is associated with a 50% depletion of microsomal heme and cytochrome P-45 concentrations in liver. The synthetic heme analogue, Sn-protoporphyrin, a potent inhibitor of heme oxygenase, lowers the activity of heme oxygenase in tumor bearing animals to below control levels. This effect is associated with a normalization of hepatic heme and cytochrome P-450 contents. These findings might have implications for protecting normal cells during tumor growth and chemotherapy.

Animals↗
PubMed1988

Cytochrome P-450C-M/F, a new constitutive form of microsomal cytochrome P-450 in male and female rat liver with estrogen 2- and 16 alpha-hydroxylase activity.

A new cytochrome P-450 isozyme, P-450C-M/F, has been purified from untreated rat liver microsomes. The purified preparation was electrophoretically homogeneous and contained 12-15 nmol of P450/mg of protein and had a minimum molecular weight of 48,500. The NH2-terminal amino acid sequence of P-450C-M/F was different from that of other P-450's. Immunoblot analysis of microsomes demonstrated that P-450C-M/F was present in the liver of untreated male as well as female rats. Treatment of rats with phenobarbital, 3-methylcholanthrene, or beta-naphthoflavone did not induce P-450C-M/F. Cytochrome P-450C-M/F exhibited little activities of 7-ethoxycoumarin and 7-ethoxyresorufin O-deethylation or hydroxylation of arylhydrocarbon, testosterone, androstenedione, and progesterone. In contrast, it was highly active in N-demethylation of ethylmorphine and benzphetamine and in 2- and 16 alpha-hydroxylation of estrogens, particularly that of estradiol. These studies establish that cytochrome P-450C-M/F is constitutively present in both male and female rats and suggest that it may be involved in the oxidative metabolism of estradiol, particularly in the formation of estriol, the uterotropic metabolite of estradiol.

Amino Acid Sequence↗
PubMed1988

Aromatization and 19-hydroxylation of androgens by rat brain cytochrome P-450.

The oxidative metabolism of androgens in the rat brain includes aromatization preceded by the requisite 19-hydroxylation. We have examined the transformation of [19-C3H3]androstenedione and [4-14C]testosterone by the semipurified cytochrome P-450 fraction of the rat brain. [19-C3H3]Androstenedione generated tritiated water and formic acid in a ratio of 8 to 1 indicating that 19-hydroxylation in the brain far exceeds that necessary for aromatization. This was confirmed by the results of the 14C-testosterone incubation in which the 14C labeled 19-hydroxy and 19-oxo derivatives which were isolated exceeded the yield of 14C-estrogens by several fold. Thus the rat brain has the capacity to form in situ 19-hydroxylated androgens which are not available to it from the circulation.

Androgens↗
PubMed1988

Development of porphyria cutanea tarda after treatment with cyclophosphamide.

Porphyria cutanea tarda, a metabolic disorder of heme biosynthesis, is characterized by cutaneous hyperpigmentation, facial hypertrichosis, dark urine, and a distinctive pattern of excess porphyrin production. Hepatic uroporphyrinogen decarboxylase activity is markedly reduced in patients with this disorder. Although porphyria cutanea tarda may be familial, it is more often sporadic in occurrence, and has been associated with excess alcohol ingestion, estrogen administration, iron overload, and several environmental hepatotoxins. It has also been associated on occasion with malignancy. We report a 46-yr-old woman with ovarian carcinoma who developed porphyria cutanea tarda while undergoing treatment with cisplatin and cyclophosphamide. The temporal course of the porphyrin abnormality suggested that cyclophosphamide was the pathogenic agent, and symptoms regressed after cessation of this drug with continued administration of cisplatin. The pathogenesis of the porphyria is not clear; however, cyclophosphamide is a substrate for cytochrome P450, and may produce metabolites that destroy this protein. The resulting increased turnover of heme might then result in overproduction of porphyrin precursors, resulting in the clinical syndrome. Studies of porphyrin metabolism in patients treated with cyclophosphamide may help to elucidate this possibility.

Cisplatin↗
PubMed1987

Partial purification of cytochrome P450 from rat brain and demonstration of estradiol hydroxylation.

Cytochrome P450 was partially purified from brain microsomes of untreated rats. A difference spectrum of the dithionite-reduced CO-complex of the purified P450 showed essentially the hemeprotein absorbing exclusively at 449 nm. The purified brain P450 was able to catalyze estradiol (E2) hydroxylation leading to the formation of 6 alpha- and 6 beta-hydroxy(OH)E2, 4-OHE2, estrone, 6-oxoE2, 2-OHE2, 15 alpha-OHE2 and estriol. These results demonstrate that rat brain P450 is active in estradiol hydroxylation.

Animals↗
PubMed1987

Proof that Sn-protoporphyrin inhibits the enzymatic catabolism of heme in vivo. Suppression of 14CO generation from radiolabeled endogenous and exogenous heme sources.

Sn-protoporphyrin (SnPP) suppresses generation of 14CO from hepatic heme labeled with delta-aminolevulinic acid (5-[14C]ALA) or from infused [14C]hemin in rats. SnPP administered 1 h before administration of 5-[14C]ALA virtually abolished the peak output of 14CO occurring 2-3 h after injection of this heme precursor, and during the succeeding 12 h reduced 14CO excretion by approximately 61% compared with controls. When [14C]hemin was infused, SnPP diminished 14CO excretion by approximately 50%. These findings, derived from experiments using radiolabeled endogenous and exogenous heme sources, establish conclusively that the synthetic metalloporphyrin SnPP inhibits the oxidative degradation of heme in the intact animal.

Aminolevulinic Acid↗
PubMed1987

Hepatoerythropoietic porphyria: clinical, biochemical, and enzymatic studies in a three-generation family lineage.

Hepatoerythropoietic porphyria is caused by a marked deficiency in the activity of uroporphyrinogen decarboxylase, an enzyme that is essential for heme biosynthesis. It has been hypothesized that uroporphyrinogen decarboxylase deficiency is inherited as a homozygous defect in the disease. This suggestion has been supported by reports of a deficiency of the enzyme in parents of patients with the disorder. Further confirmation would be provided by demonstrating a similar uroporphyrinogen decarboxylase deficiency in the offspring of such patients. This study follows the enzymatic defect throughout three generations of a family in which a second-generation male was shown to have hepatoerythropoietic porphyria. Detailed biochemical and enzymatic analyses revealed a moderate deficiency of uroporphyrinogen decarboxylase in both the proband's parents and in his three children, all of whom were asymptomatic. The mildness of the clinical symptoms in the proband correlated with a higher level of residual enzyme activity than that in previously described patients. We conclude that clinically manifested hepatoerythropoietic porphyria results from the homozygous inheritance of a defect in the uroporphyrinogen decarboxylase gene, that the severity of clinical symptoms is probably related to the level of residual enzyme activity, and that the genetic defect of uroporphyrinogen decarboxylase in hepatoerythropoietic porphyria can be heterogeneous.

Adult↗
PubMed1987

Drug metabolism by the human hepatoma cell, Hep G2.

The human liver-derived cell line, Hep G2, has aryl hydrocarbon hydroxylase and 7-ethoxycoumarin o-de-ethylase activities. Partial purification of cytochrome P-450 from Hep G2 cells provided spectral evidence of this hemeprotein in the purified fraction. These results suggest that Hep G2 cells will be useful for the study of cytochrome P-450 and the regulation of mixed function oxidase activities in liver cells of human origin.

7-Alkoxycoumarin O-Dealkylase↗
PubMed1987

[Effects of ACTH or hCG on corticosterone and progesterone secretion from adrenal glands of the rats at various ages].

Effects of ACTH or hCG on the secretion of corticosterone (CB) and progesterone (PRG) from adrenal glands of the female rats at various ages were studied. In in vitro experiment, adrenal gland cells were isolated from fetal, neonatal, immature and adult rats by the method described by us before and were incubated in MEM. We chose to designate the hormones in the medium as hormone secretion. In in vivo experiment, hormones in the serum were determined. In vitro experiment, in which ACTH was added to the medium, indicated that CB was low in the media containing the cells from fetal and neonatal glands compared to those from immature and adult. PRG was elevated by ACTH addition at all of the ages. hCG addition had no effects on both CB and PRG in the media of immature and adult rats. In vivo experiment, in which ACTH was injected s.c., indicated that the response of serum PRG was slightly earlier than the CB response and peaked with a subsequent decline in immature rats. The results suggest that adrenal gland responds to ACTH from fetal age and secrets PRG, but little of CB in fetal age.

Adrenal Glands↗
PubMed1987

Analysis of porphyrins and enzymes in porphyrin synthesis in Taenia solium cysticercus from man and pig.

Porphyrins and activities of heme biosynthetic enzymes in Taenia solium cysticerci from porcine and human hosts, were examined in order to clarify the possible step where heme synthesis is interrupted. Porphyrins in the vesicular fluid of the parasite were predominantly coproporphyrin, followed by penta-carboxylated porphyrin, which together accounted for 90% of the accumulated porphyrins. Coproporphyrin and penta-carboxylated porphyrin were both type I and III isomers. Small amounts of protoporphyrin and uroporphyrin, and trace amounts of tri-, hexa- and hepta-carboxylated porphyrins were also detected. Fluorescence and phosphorescence spectra and lifetime studies revealed that at least 75% of the porphyrins were bound to metal, probably Zn, while the rest was free. Reverse phase high performance liquid chromatography monitored at an excitation wavelength of 417 nm and at an emission wavelength of 585 nm demonstrated that approximately 90% of these porphyrins were Zn-coproporphyrin. A fluorescence excitation peak at 283 nm with an emission peak at 585 nm and 625 nm indicated that some of the porphyrins were associated with proteins in the vesicular fluid of the parasite. Low levels of delta-aminolevulinic acid dehydratase, porphobilinogen deaminase and uroporphyrinogen decarboxylase activities, and heme concentrations were found in the extract of the parasite walls and scolex, but not in the vesicular fluid. The porphyrin accumulation pattern in this parasite can best be explained by postulating a deficiency of coproporphyrinogen oxidase activity, similar to that in human patients with hereditary coproporphyria. A parasite dissected from a human host was considerably less porphyric than those from pigs, but the pattern of accumulated porphyrins was quite similar in both. In view of their porphyrin contents, T. solium cysticerci could be light sensitive.

Animals↗
PubMed1987

Porphyria cutanea tarda associated with the acquired immune deficiency syndrome.

Three male subjects with cutaneous symptoms and biochemical signs typical of porphyria cutanea tarda (PCT) developed acquired immune deficiency syndrome (AIDS). All three were in a classic high risk group for the latter disease and developed a typical progressive illness. Two patients succumbed to opportunistic infections; the third is alive but critically ill. The symptomatic prodrome of AIDS developed concurrently with or followed the onset of symptoms of PCT in all three individuals. PCT and AIDS are both uncommon disorders; their association in three patients is thus of inherent clinical interest. If this association is not coincidental, it raises the possibility that the occurrence of photosensitivity, skin lesions, and evidence of biochemical changes characteristic of PCT may, in certain patients at risk for AIDS, presage the subsequent full clinical expression of the latter disease.

Acquired Immunodeficiency Syndrome↗