Biomedical subjects

R Bortell

Publications and source records attributed to R Bortell.

41 records · Page 3Linked to original sources

PubMed1990

Coordinate occupancy of AP-1 sites in the vitamin D-responsive and CCAAT box elements by Fos-Jun in the osteocalcin gene: model for phenotype suppression of transcription.

Osteocalcin, a bone-specific protein and marker of the mature osteoblast, is expressed only in nonproliferating osteoblasts in a mineralizing extracellular matrix, while type I collagen is expressed in proliferating cells. The nuclear proteins encoded by the c-fos and c-jun protooncogenes are expressed during the proliferation period of osteoblast phenotype development. We present evidence that AP-1 (HeLa cell-activating protein 1) sites residing within two promoter elements of the osteocalcin gene bind the Fos-Jun protein complex: the osteocalcin box (OC box; nucleotides -99 to -76), which contains a CCAAT motif as a central element and influences tissue-specific basal levels of osteocalcin gene transcription, and the vitamin D-responsive element (VDRE; nucleotides -462 to -440), which mediates enhancement of osteocalcin gene transcription. Gel electrophoretic mobility-shift analysis demonstrated high AP-1 binding activity in proliferating osteoblasts and dramatic changes in this activity after the down-regulation of proliferation and the initiation of extracellular-matrix mineralization in primary cultures of normal diploid osteoblasts. Methylation interference analysis established at single nucleotide resolution that purified recombinant Fos and Jun proteins bind in a sequence-specific manner to the AP-1 sites within the VDRE and OC box. Similarly, an AP-1 motif within a putative VDRE of the alkaline phosphatase gene, which is also expressed after the completion of proliferation, binds the Fos-Jun complex. These results support a model in which coordinate occupancy of the AP-1 sites in the VDRE and OC box in proliferating osteoblasts may suppress both basal level and vitamin D-enhanced osteocalcin gene transcription as well as transcription of other genes associated with osteoblast differentiation--a phenomenon we describe as phenotype suppression. This model is further supported by binding of the Fos-Jun complex at an AP-1 site in the type alpha I collagen promoter that is contiguous with, but not overlapping, the VDRE. Such a sequence organization in the collagen VDRE motif is compatible with vitamin D modulation of collagen but not with osteocalcin and alkaline phosphatase expression in proliferating osteoblasts.

Animals↗

PubMed1988

Synthetic polyamine analogues as antineoplastics.

In this paper, we report on the synthesis and biological activity of a number of N-alkylated spermine compounds. The dialkylspermines N1,N12-dimethylspermine (DMSPM-2), N1,N12-diethylspermine (DESPM-3), and N1,N12-dipropylspermine (DPSPM-4) are all shown to inhibit the growth of L1210 cells in culture with IC50 values of less than 1 microM at 96 h. Furthermore, DESPM-3 is shown to be similarly active against Daudi and HL-60 cells in culture. A structure-activity relationship is shown to exist between the position at which spermine is alkylated and its antiproliferative properties. The activity of 10 microM DESPM-3 against L1210 cells was shown to be cytostatic, with greater than 90% cell viability by trypan blue exclusion, even after a 144-h exposure. When L1210 cells were treated with 10 microM DESPM-3 over a 144-h period, their size and mitochondrial DNA content were gradually but substantially diminished. However, flow cytometric measurements of the nuclear DNA content of these treated cells at 96 h indicated only slightly reduced S and G2 populations and significant changes only after 144 h. A cloning assay performed on the cells after 96 h of exposure to this drug (10 microM) indicated that the cells were not growing. Finally, when male DBA/2 mice, inoculated with L1210 leukemia cells, were treated with DESPM-3, their life span was increased in excess of 200% relative to untreated controls. Moreover, many long-term survivors were apparently tumor free at the end of the experiment (60 days).

Animals↗

PubMed1986

Nitrofurantoin inhibition of mouse liver mitochondrial respiration involving NAD-linked substrates.

In our study, nitrofurantoin (NF) and nitrofurazone (NZ) inhibited respiration of isolated mouse (C57B/6J, adult, male) liver mitochondria. Other aromatic nitro compounds, nitroimidazole, metronidazole, and p-nitrobenzoic acid, did not have any significant effect. The primary site of activity for NF was complex I NADH-ubiquinone oxidoreductase mediated respiration, since only complex I substrates, glutamate, beta-hydroxybutyrate, and alpha-ketoglutarate-mediated respiration were decreased. Respiration supported by succinate, a complex II substrate, was not affected by any of the compounds. NF at a concentration of 50 microM decreased state 3 and dinitrophenol-uncoupled respiration to 28 +/- 1 and 25 +/- 5% of control, respectively, of mitochondria oxidizing glutamate. Studies with mitoplasts oxidizing glutamate showed that NF inhibited both state 3 and 4 respiration. The inhibition of state 3 was prevented by the simultaneous addition of superoxide dismutase (240 micrograms/ml) and catalase (200 micrograms/ml). These results suggest that the mitochondrion, in particular complex I of the electron transport system, is a target for NF toxicity. The effect on respiration may be mediated by NF redox cycling and the generation of reactive oxygen intermediates resulting in the interference of electron flow.

Animals↗

PubMed1983

Acute experimentally induced aflatoxicosis in the weanling pony.

Nineteen weanling ponies and 1 adult pony were given a single oral dose of aflatoxin B1 (AFB1). Dosages were: 0, 0.5, 1, 2, 4, 5, 6, and 7.4 mg of AFB1/kg of body weight. Vital signs were monitored, and whole blood and serum collected for analysis of serum enzymes, prothrombin time, blood cell counts, and serum urea nitrogen. Ponies that died were examined for gross lesions, and tissues were collected for histopathologic examination and analysis of AFB1 and AFM1 residues. Two of the 4 ponies given the 2 mg/kg dose and all ponies given the larger dosages died within 76 hours. Clinical signs included increased rectal temperature, faster heart and respiratory rates, abdominal straining, bloody feces, and tetanic convulsions. At necropsy, ponies that died of acute aflatoxicosis showed visceral petechiae and hepatic focal lesions. Histopathologic changes included severe hepatic necrosis, vacuolation, and bile duct hyperplasia. Aflatoxins B1 and M1 were recovered from liver, kidney, skeletal muscle, and gastrointestinal contents. One other pony given the 2 mg/kg dose died 32 days after dosing, and 1 control pony died after 70 days. Continuous elevations in prothrombin time and serum aspartate aminotransferase, alanine aminotransferase, and gamma-glutamyl transpeptidase levels were observed in ponies dosed at 4 mg/kg or more. Significant (P less than 0.05) elevations in these values, which peaked 2 to 3 days after dosing, were seen in ponies given the 2 mg/kg dose. This group also had significant increases over controls in PCV and hemoglobin concentration 5 days after dosing.

Acute Disease↗

PubMed1980

Plasma concentration of iditol dehydrogenase (sorbitol dehydrogenase) in ponies treated with aflatoxin B1.

Twelve clinically normal Shetland ponies were allocated to one of four treatment groups. Aflatoxin B1 was administered at the dosage level of 2 mg/kg of body weight to group A, 1 mg/kg to group B, and 0.5 mg/kg to group C; a placebo was given to group D (controls). Plasma samples were assayed at 4-hour intervals for iditol dehydrogenase (ID) (sorbitol dehydrogenase) concentrations as an indicator of hepatic damage. One of the ponies in group A died 68 hours after dosing; another pony in group A died 76 hours after dosing. All other animals survived the experiment. The means of peak ID values were as follows: group A, 1514.0 IU/l (P < 0.05); group B, 192.6 IU/L (P < 0.05); group C, 8.5 IU/L (P < 0.05); and group D (controls), 2.7 IU/L. A square root transformation analysis of the postdosing response of ID values in relation to time demonstrated that the mean of group A became significantly higher (P < 0.05) than did the mean of the control group at 5 to 6 hours. The mean of group B at 12 to 16 hours and the mean of group C at 20 to 24 hours also were significantly higher (P < 0.05) than was the mean of the control group.

Administration, Oral↗