Lanosterol 14-demethylase activity expressed in rat brain microsomes

The occurrence of sterol 14-demethylase in rat brain microsomes was confirmed. The brain microsomes from adult rats converted lanosterol into its 14-demethylated products, 4,4-dimethylcholesta-8, 24-dienol, and 4,4-dimethylcholesta-8,14,24-trienol, in the presence of NADPH and molecular oxygen. This metabolism of lanosterol was inhibited by carbon monoxide and ketoconazole, a potent inhibitor of sterol 14-demethylase P450 (P45014DM or CYP51). These facts indicated the occurrence of lanosterol 14-demethylation in rat brain microsomes and its dependency on P45014DM. A representative value of the lanosterol demethylase activity of the brain microsomes was 8.4 pmol/min/mg protein or 640 pmol/ min/nmol of total P450. The former was about one-thirteenth of the corresponding value observed with liver microsomes from the same rats, while the latter was 4-times higher than the corresponding value obtained with the liver microsomes. This fact suggested that the ratio of P45014DM to other P450 species was higher in brain than in liver. Lanosterol 14-demethylation is situated at the root of the sterol-biosynthetic branch of the mevalonic acid pathway. Therefore, the present finding enzymologically supports the existence of the sterol biosynthetic pathway in brain.

A novel donor splice site mutation in the glycogen debranching enzyme gene is associated with glycogen storage disease type III

Analysis of glycogen debranching enzyme (debrancher) cDNA from a patient with glycogen storage disease type III revealed a deletion of 124 base pairs. A donor splice site mutation (IVS G+1 to T) was identified in the patient's debrancher gene, which caused exon skipping of the upstream exon and resulted in a truncated enzyme due to premature termination. Mutational analysis of the patient's family showed that this point mutation was inherited from the father. Southern blot analysis of the patient's genomic DNA showed an additional, unique EcoRI fragment of 5.8 kb, which was inherited from the mother. These results suggested that the patient was a compound heterozygote for the donor splice site mutation, which is the first identified in the debrancher gene, and had a genetic defect relating to an aberrant 5.8-kb EcoRI fragment.

Sterol 14-demethylase P450 activity expressed in rat gonads: contribution to the formation of mammalian meiosis-activating sterol

Sterol 14-demethylase P450 (P45014DM)-dependent formation of 4,4-dimethylcholesta-8,14,24-trienol, that has been reported for a mammalian meiosis-activating sterol, in rat ovaries was confirmed. Transient elevation of ovarian P45014DM activity, that might be related to the female sexual cycle of rat, was observed. The P45014DM activity of immature ovaries was induced by pregnant mare's serum gonadotropin. These facts suggest the contribution of ovarian P45014DM to the gonadotropin-dependent formation of the meiosis-activating sterol, and provide a clue to understanding the mechanism how gonadotropins initiate the resumption of meiosis of mammalian oocytes. It was also found that rat testicular P45014DM participated in the production of 4,4-dimethylcholesta-8,24-dienol that was reported for another meiosis-activated sterol isolated from bull testes.

Sterol 14-demethylase P450 (P45014DM*) is one of the most ancient and conserved P450 species

To determine the orthology of sterol 14-demethylase (P45014DM), the only known P450 enzyme distributed widely in eukaryotes with a conserved metabolic role, the full-length amino acid sequences of rat and human P45014DMs were determined from the cloned cDNA sequences, and compared with those of the corresponding fungal proteins (CYP51). The amino acid identity value between given pairs of P45014DMs ranged from 93% (human/rat) to 39% (human or rat/Saccharomyces cerevisiae). All the P45014DMs formed a single cluster in a phylogenetic tree constructed from representative P450 protein sequences currently available. The nearest neighbors to the P45014DM cluster in the phylogenetic tree were CYP7 (cholesterol 7 alpha-hydroxylase) and CYP8 (prostacyclin synthase), and the divergence point of fungal and mammalian P45014DMs was clearly more recent than that of P45014DM and CYP7/CYP8. These lines of evidence show that fungal and mammalian P45014DMs are really orthologous. This is the first example of orthologous P450s occurring in distinct kingdoms. P45014DM may be an ancient P450 which arose before the divergence of major eukaryotic branches and has been conserved throughout evolution. The amino acid identity value (93%) between human and rat P45014DMs was comparable to those observed for some housekeeping enzymes. In addition, a processed pseudogene of P45014DM was found in a rat genomic DNA library, suggesting the expression of P45014DM in germ line cells. These facts suggest that P45014DM may be a housekeeping enzyme essential for the viability of mammals.

Protein kinase C-dependent down-regulation of basic fibroblast growth factor (FGF-2) receptor by phorbol ester and epidermal growth factor in porcine granulosa cells

The regulation of the basic fibroblast growth factor (bFGF, or FGF-2) receptor on porcine granulosa cells was studied. Receptor levels before and after cell differentiation in vivo and in vitro did not show any significant changes. Dibutyryl cAMP and the protein kinase A (PKA) inhibitor H-8 had no effect on bFGF binding. These results suggest that PKA was not involved in the receptor expression. Treatment of the granulosa cells with phorbol 12-myristate 13-acetate (PMA), a protein kinase C (PKC) activator, progressively decreased the number of bFGF receptors to about 20% of their initial levels after 8 h, and this effect occurred in a concentration- and time-dependent manner. Similarly, synthetic diacylglycerol also inhibited bFGF binding. The highly specific PKC inhibitor GF109203X completely prevented the reduction of bFGF binding by PMA and diacylglycerol. Kinetic analyses of the turnover of cell surface bFGF receptors in the presence of cycloheximide showed that PMA accelerated loss of receptors from the cell surface, suggesting the enhanced receptor internalization by PMA resulting in the receptor reduction. PMA did not influence steady-state FGF receptor messenger RNA levels. PMA induced an increased PKC activity in the membrane fraction, and among PMA sensitive PKC alpha, beta II, delta and epsilon, only PKC alpha was readily detected by immunoblotting and translocated to the membrane fraction. PMA-pretreated cells showed negligible effect on c-fos messenger RNA induction in response to bFGF stimulation, indicating a functional reduction of receptors. When cells were incubated with epidermal growth factor, receptor levels were reduced, but this effect was not observed in the presence of GF109203X. These results suggest that the bFGF receptor in porcine granulosa cells is regulated by the PKC, not PKA, pathway in an isoenzyme-specific fashion and that its possible mechanism may involve regulation of receptor internalization.

Involvement of phospholipase D in ganglioside GQ1b-induced biphasic diacylglycerol production in human keratinocytes

Ganglioside IV3 (NeuAc)2, II3 (NeuAc)2-GgOse4Cer (GQ1b), which induces terminal differentiation in keratinocytes, was previously found to enhance the mass content of inositol 1,4,5-trisphosphate and intracellular calcium concentration ([Ca++]i), peaking at 30 seconds. In the present study, the biphasic accumulation of 1,2 diacylglycerol, i.e., the first transient and the second sustained phase, was observed in cultured human keratinocytes stimulated by GQ1b. On the other hand, II3 NeuAc-LacCer (GM3), which inhibits keratinocyte proliferation without inducing differentiation, did not cause diacylglycerol formation. Phosphatidylethanol, produced by transphosphatidylation and a potential marker for phospholipase D activity, was produced by the exposure to GQ1b in the presence of ethanol. The second sustained phase of diacylglycerol was repressed by ethanol, indicating that the diacylglycerol-formation pathway via phospholipase D followed by phosphatidic acid phosphohydrolase would in part account for the second diacylglycerol phase. Furthermore, this second phase of GQ1b-induced diacylglycerol generation was reduced by pretreatment with propranolol, an inhibitor of phosphatidic acid phosphohydrolase. In addition, the levels of [3H]choline, a direct metabolite of the phospholipase D pathway, were elevated within 1 min after GQ1b addition and then sustained for at least 20 min. Taken together, the results suggest that the phospholipase D pathway may contribute to the second phase of diacylglycerol formation, which might be involved in differentiation.

Involvement of protein kinase C in bradykinin-induced intracellular calcium increase in primary cultured human keratinocytes

Bradykinin (BK) is one of the key mediators of inflammation and a weak mitogen. We have previously demonstrated that BK induced the generation of inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) which caused Ca2+ mobilization in human keratinocytes. In this study, BK-induced Ca2+ responses were examined in primary cultured human keratinocytes by video imaging fluorescence microscopy using fura-2. Intracellular calcium concentration ([Ca2+]i) level increased to a peak within 30 s after BK addition and decreased gradually to the basal level. The existence of the broad shoulder in the [Ca2+]i profile was suggested to be due to the Ca2+ influx from the external medium, because this disappeared in the presence of 0.5 mM EGTA. Pretreatment with phorbol-12-myristate-13-acetate (PMA), a protein kinase C (PKC) activator, significantly resulted in reduction of the descending shoulder of BK-induced increase in [Ca2+]i. A 20-min pretreatment with PKC inhibitors, H-7 or staurosporine, reversed the decrease by PMA in the shoulder of BK-induced Ca2+ response. Furthermore, the BK-induced [45Ca] uptake was inhibited by EGTA and PMA. Ins(1,4,5)P3 generation induced by BK peaked at 20 s and returned to the basal level at 60 s. There were no significant differences in Ins(1,4,5)P3 levels at 20 and 60 s among the cells exposed to BK alone, BK with PMA pretreatment (20 min) and BK with PMA+H-7 pretreatment. These results suggest that the BK-induced Ca2+ influx, which was shown as shoulder, may be negatively modulated by PKC in primary cultured human keratinocytes.

Resected early gastric cancer--clinicopathological studies on 610 cases

A total of 610 cases of early gastric cancer were studied, retrospectively. Of these, 541 (88.7%) cases were single and 62 (10.1%) cases were multiple cancers. Lymph node metastasis occurred in 11.2% of the elevated, in 8.2% of the depressed and in 15.1% of the mixed type. There was no lymph node metastasis when a mucosal or submucosal cancer was less than 10 mm in diameter. By contrast, in the cases in which the preoperative diagnosis was suspected advanced cancer, the incidence of lymph node metastasis was high, at 33%. Therefore, when the preoperative diagnosis is advanced cancer, standard radical gastrectomy and/or extended radical gastrectomy should be selected even though they are found to be early gastric cancer. The age-corrected 5-year survival rate was 98.5% in the cases with no lymph node metastasis and 93.0% in the cases with lymph node metastasis (p > 0.05). The 5-year survival rate was 100% in mucosal cancer and 95.5% in submucosal cancer (p > 0.05).

Synthesis of 9E- and 9Z-locked retinoic acid analogs as ligands for RAR and RXR

New retinoic acid (RA) analogs 9E-locked-RA 3 and 9Z-locked-RA 4 were synthesized from dithiane 6 and beta-cyclocitral 13, respectively. Both analogs behaved as agonistic ligands for a mixture of retinoic acid receptor (RAR) and retinoid X receptor (RXR).

Effect of long-term methotrexate-induced neutropenia on experimental periodontal lesion in rats

The effects of long-term methotrexate (MTX)-induced neutropenia on the periodontal lesion in rats were investigated histologically, histometrically and bacteriologically. A nylon thread was inserted into the interdental gingiva between the 1st and 2nd right maxillary molars of the animals 3 weeks before an application of MTX. The animals were then divided into Groups A and B. Group B were injected intraperitoneally with 1.0 mg/kg of MTX 3 times per week for 9 weeks. Group A received saline as a control. Five animals were killed at the 1st, 3rd, 5th, 7th, and 9th week. In Group A, the neutrophils did not decrease during these 9 weeks. In Group B, however, the neutrophils decreased during the 3rd to 9th week. Whereas the experimental side of Group A showed only moderate alveolar bone resorption between the 7th and 9th week, [in Group B] a marked alveolar bone resorption occurred in Group B occurred in the same period. Alveolar bone loss in the experimental side of Group B was significantly greater (p < 0.01) than in Group A in the 7th to 9th weeks. The percentage of gram-negative rods increased in both control and experimental sides of Group at the 9th week. The results of the present study indicate that neutropenia is induced by a long-term application of MTX in rats and that alveolar bone destruction increases as time goes by in the area where a nylon thread was inserted.

Selectivity of isoprenoid-containing imidazole antifungal compounds for sterol 14-demethylase P450 (P450(14)DM) and 7-ethoxycoumarin O-deethylase P450 of rat liver microsomes

The imidazole antifungal compound AFK-108 (1-[2-(2,4-dichlorophenyl)-2-((2E)-3,7-dimethylocta-2,6- dienyloxy)ethyl]-1H-imidazole) has been shown to be a potent inhibitor for yeast lanosterol 14 alpha-demethylase (P450(14)DM), interacting specifically with the sterol side-chain recognition part of the substrate site through its geranyl moiety. AFK-108 acted as a potent inhibitor for rat liver P450(14)DM, while its farnesyl (AFK-110) and prenyl (AFK-122) homologues were weak inhibitors. This indicates that AFK-108 interacts with rat liver P450(14(DM in the same manner as with the yeast enzyme. However, the difference between the potency of AFK-108 and the homologues was greater in rat P450(14)DM than in the yeast enzyme. AFK-108 and its homologues partially inhibited 7-ethoxycoumarin O-deethylase activity of rat liver microsomes. The order of potency was AFK-122 > AFK-108 > AFK-110, indicating that some steric hindrance of the isoprenoid moiety might affect their potency. The inhibitory effect of AFK-108 for P450(14)DM was considerably higher than for 7-ethoxycoumarin O-deethylase P450, while the inhibition of AFK-110 and AFK-122 on these enzymes was of the same order of magnitude. These results suggest that azole compounds interacting with the side-chain recognition site of P450(14)DM may be good candidates as antifungal agents selective for fungal P450(14)DM.

Occurrence of a P450 showing high homology to yeast lanosterol 14-demethylase (P450(14DM)) in the rat liver

The rat liver cDNA library in lambda gt11 was screened with the antisera against rat liver lanosterol 14 alpha-demethylase (P450(14DM)), and one clone (pRT-9) was isolated. The open reading frame of pRT-9 cDNA showed high homology to yeast P450(14DM) (48.9% in nucleotides and 37.7% in amino acids). Homology of the heme-binding region of pRT-9 protein to that of yeast P450(14DM) was 80%. Three additional regions showing more than 60% homology were identified and one of them was assignable as the distal helix. These findings suggest that pRT-9 protein is P450(14DM) and P450(14DMs) of rat and yeast may be orthologous. This is the first evidence suggesting the occurrence of orthologous P450 in widely diverged species.

Radiation surface doses to patients and staff during positron emission tomography

In view of the complexities involved in estimating individual organ doses in positron emission tomography, the present study was undertaken to measure radiation surface doses in 23 patients undergoing PET studies using specially designed CaSO4: Tm TL dosimeters. In patients with brain disorders, the mean radiation surface doses to the chest and gonads were 0.52 mGy and 0.47 mGy, respectively. In patients with cardiac disorders, the mean surface doses to the forehead and gonadals were, respectively, 0.29 mGy and 0.41 mGy. It was possible to measure the radiation surface doses to all the intended sites in patients with liver malignancies, and maximum surface doses of 0.50 mGy and 0.49 mGy were recorded at the chest and gonadals, respectively. The measurement of radiation surface doses enables easy, quick, and reliable intercomparison of radiation load to patients and staff in various PET procedures.

Purification of chondroitin 6-sulfotransferase secreted from cultured chick embryo chondrocytes

Chondroitin 6-sulfotransferase, which transfers sulfate from 3'-phosphoadenylyl sulfate to position 6 of N-acetylgalactosamine in chondroitin, was purified 1,430-fold to apparent homogeneity with a 22% yield from the serum-free culture medium of chick embryo chondrocytes by affinity chromatography on heparin-Sepharose CL-6B, wheat germ agglutinin-agarose, and 3',5'-ADP-agarose. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the purified enzyme showed a single broad protein band with an apparent molecular weight of 75,000. Since the purified enzyme has an apparent molecular weight of 160,000 as judged by gel chromatography on Superose 12, the active form of chondroitin 6-sulfotransferase may be a dimer. The purified enzyme transferred sulfate to chondroitin, chondroitin sulfate, and corneal keratan sulfate. Chondroitin sulfate E from squid cartilage, dermatan, sulfate, and heparan sulfate hardly served as acceptors of the sulfotransferase. The sulfated product derived from keratan sulfate was degraded by keratanase but not by chondroitinase ABC.

Recombinant human granulocyte colony-stimulating factor accelerates regeneration after T-2 toxin-induced hemopoietic injury and lessens lethality in mice

The effects of rhG-CSF on T-2-induced leukopenia and lethal toxicity in mice were investigated. First, T-2 was administered by gavage to adult male mice at a dose of 3 mg/kg b.w. daily for 7 days, and rhG-CSF was given i.p. in daily dose of 10 or 30 micrograms/kg b.w./day, beginning on the 2nd day, for 5 days. The peripheral WBC of mice receiving T-2 alone was decreased to one fourth of control counts, and bone marrow (BM) cell counts were also markedly diminished. The administration of rhG-CSF prevented those T-2-induced depressions. Histologically, the delation of the hematopoietic cells from BM and spleen of mice given T-2 was remarkably counteracted by administration of rhG-CSF. In the other experiment, rhG-CSF was injected i.p. for 5 days beginning on the next day of the 7-day T-2 administration. The recovery of WBC and BM cell counts was hastened by rhG-CSF reaching the control level in 6 days, and differential leukocyte analysis revealed an increase of neutrophils. Furthermore, simultaneous administration of rhG-CSF depressed the T-2-induced lethal toxicity, dose-dependently. The results revealed that rhG-CSF possesses a potent ability to protect T-2-induced leukopenia and lethality in mice, and it could be as an antidote against T-2 and related trichothecene-induced acute intoxication.

Activities of some regulatory enzymes of carbohydrate metabolism in the liver of rats fed a histidine-excess diet

1. Glycogen is accumulated in the liver of rats given a histidine-excess diet. 2. In order to know the regulatory point, the activities of eight hepatic key enzymes in the carbohydrate metabolism were measured after feeding either a basal or a histidine-excess diet for 0, 3 and 7 days. 3. The active glycogen synthase level was about 2.6- and 3.0-fold higher after feeding for 3 and 7 days, respectively, but the total activity of this enzyme was not affected after feeding for 3 days and was increased after feeding for 7 days. 4. The active glycogen phosphorylase, glucose 6-phosphatase and pyruvate kinase activities were significantly decreased, and fructose 1,6-bisphosphatase activity was increased on a histidine-excess diet for 3 days. 5. Thus, of these enzymatic changes, mainly the enhancement of active glycogen synthase might lead to the substantial accumulation of hepatic glycogen. 6. The in vivo incorporation of radioactive glucose into liver glycogen was stimulated in rats given a histidine-excess diet.

Inhibition by a novel azole antifungal agent with a geranyl group on lanosterol 14 alpha-demethylase of yeast

AFK-108 (1-[2-(2,4-dichlorophenyl)-2-((2E)-3,7-dimethylocta-2,6- dienyloxy)ethyl]-1H-imidazole) is a new imidazole derivative characterized by a geranyl substituent showing strong antifungal activity. Azole antifungal agents are known to be potent inhibitors of lanosterol 14 alpha-demethylase (P450(14)DM) of fungi. The role of the geranyl group of AFK-108 on interaction of AFK-108 with the target was studied by using Saccharomyces cerevisiae P450(14)DM as the model enzyme. AFK-108 and some of its derivatives bound to oxidized P450(14)DM with one-to-one stoichiometry and inhibited the demethylase activity. AFK-108 derivatives having the longer farnesyl or the shorter prenyl group showed lower affinity than AFK-108 for the enzyme. AFK-108 caused 100% inhibition at the equivalent concentration to P450(14)DM in the reaction mixture (0.07 microM), while the farnesyl derivative inhibited the activity by 60% at the same concentration. AFK-108 interfered with the binding of CO to the ferrous P450(14)DM. However, the interfering effect of the prenyl derivative was lower than that of AFK-108. Another AFK-108 derivative having the saturated 3,7-dimethyloctyl group was also a weaker inhibitor than AFK-108. These experiments suggest that the geranyl group of AFK-108 interacts with the substrate binding site of P450(14)DM that recognises the side chain of the substrate. AFK-108 is the first example of an azole derivative interacting with the side chain recognising region of the substrate binding site of P450(14)DM.

The effect of a histidine-excess diet on cholesterol synthesis and degradation in rats

Feeding a diet high in excess histidine (5% L-histidine) resulted in hypercholesterolemia and enlargement of the liver in rats. To clarify the mechanism of the hypercholesterolemia, cholesterol synthesis and degradation were followed. We found that hepatic 3-hydroxy-3-methylglutaryl-coenzyme A reductase activity in histidine-excess diet rats was significantly higher than in rats fed a basal diet. Incorporation of [3H] water into cholesterol of liver slices from rats fed the histidine-excess diet was higher than incorporation into liver slices from rats fed the basal diet (expressed per liver per 100 g body weight). In vivo incorporation of [3H] water into hepatic cholesterol was also higher, but the incorporation into cholesterol of the small intestine was lower in histidine-fed rats than in rats fed the basal diet (expressed per liver per 100 g body weight). Hepatic cholesterol 7 alpha-hydroxylase activity was similar in both groups. The data suggest that the hypercholesterolemia caused by histidine-excess diet appears to be due to the stimulation of cholesterol synthesis in the liver.

[Biological effects of exposure to high frequency electromagnetics on rabbits and guinea pigs]

To investigate the biological effects of exposure to feeble high frequency electromagnetism, skin surface temperature, blood vessel (arterioles and venules) diameter were examined, using infrared thermography, a laser doppler flowmeter, and a video microscope, respectively, in the ear of rabbits. After exposing the ear of rabbits to high frequency electromagnetism value of 9 MHz for 15 minutes, continued rising of local temperature was demonstrated. Though dilatation of arterioles was not seen. In addition, venules tended to dilate and blood flow also to increase, and microcirculation was accelerated at the site where electromagnetism was exposed. Hazardous effects of long term exposures of high frequency electromagnetism (9 MHz for 30 days, 8 hours/day) on guinea pigs were not observed in their behavior, food consumption, body and organ weights, hematological and biochemical values, macroscopic and microscopic findings on autopsy.

Structural analysis of the interaction between the side-chain of substrates and the active site of lanosterol 14 alpha-demethylase (P-450(14)DM) of yeast

The role of the side-chain of lanosterol in the enzyme-substrate interaction of yeast P-450(14)DM (lanosterol 14 alpha-demethylase) was analyzed with lanosterol derivatives having functional groups on the side-chain. Purified P-450(14)DM from Saccharomyces cerevisiae catalyzed 14 alpha-demethylation of 26-hydroxylanosterol and 25-hydroxy-24,25-dihydrolanosterol with a lower activity than lanosterol and 24,25-dihydrolanosterol. This enzyme demethylated the (Z)-24-ethylidene-24,25-dihydrolanosterol with a low rate, but did not metabolize the E-isomer. The apparent Km of 26-hydroxylanosterol was 10.8 microM, which was higher than that of lanosterol, but lower than that of 24,25-dihydrolanosterol. On the other hand, competition experiments suggested that the affinity of 25-hydroxy-24,25-dihydrolanosterol and (Z)-24-ethylidene-24,25-dihydrolanosterol for P-450(14)DM was significantly lower than that of 24,25-dihydrolanosterol. Integration of the present results with the preceding ones (Aoyama, Y., Yoshida, Y., Sonoda, Y. and Sato, Y. (1991) Biochim. Biophys. Acta, 1081, 262-266 and Aoyama, Y. and Yoshida, Y. (1991) Biochem. Biophys. Res. Commun., 178, 1064-1071) suggests that yeast P-450(14)DM recognizes two parts of the side-chain, the structure around C-24 and the terminal fork consisting of C-25, C-26 and C-27.