PubMed Health⌕ Search

Biomedical subjects

M K Haddox

Publications and source records attributed to M K Haddox.

At least 19 recordsLinked to original sources
PubMed1991

Reconstitution of isolated Ca(2+)-activated K+ channel proteins from basolateral membranes of rabbit colonocytes.

Using calmodulin-affinity chromatography, we have isolated a fraction of proteins from solubilized basolateral membranes of rabbit colonocytes which when reconstituted into planar phospholipid bilayers disclosed Ca(2+)-activated single K+ channel activities. The properties of the reconstituted channels are identical to those of native membrane vesicles incorporated into these bilayers with respect to their high selectivity for K+ over C-, high ("maxi") conductance, voltage gating, and inhibition by trifluoperazine. Two-dimensional sodium dodecyl sulfate gel electrophoresis of these proteins revealed three major protein species with molecular masses of 120, 60, and 35 kDa, which constituted 70, 10, and 20%, respectively, of the total protein. The results of other studies strongly suggest that the 35-kDa protein may be the Ca(2+)-activated K+ channel protein in these membranes.

Animals↗
PubMed1990

Phosphorylation of ornithine decarboxylase by casein kinase II from RAW264 cells.

Casein kinase II and ornithine decarboxylase were purified from a virally-transformed macrophage-like cell line, RAW264. The addition of casein kinase II to a reaction mixture containing [tau-32P]GTP, Mg++, and ornithine decarboxylase led to the phosphorylation of a 55,000 dalton protein band in the purified preparation of ornithine decarboxylase. Stoichiometric estimates indicated that casein kinase II incorporated 0.15 mole of phosphate per mole of ornithine decarboxylase, which was increased to 0.3 mole/per mole in the presence of spermine. The apparent Km and Vmax values for the casein kinase II-mediated phosphorylation of ornithine decarboxylase were 0.36 microM and 62.5 nmol/min./mg kinase. The addition of spermine to the reaction did not alter the Km but increased the Vmax to 100 nmol/min./mg kinase. The phosphorylation of ornithine decarboxylase by casein kinase II affected neither the rate of maximal ornithine decarboxylase activity nor the affinity of the enzyme for ornithine.

Amino Acids↗
PubMed1989

Mononuclear cell polyamine content associated with myeloid maturation in patients with leukemia during administration of polyamine inhibitors.

Fourteen patients with acute leukemia in relapse were treated with difluoromethylornithine (DFMO) alone or in combination with methylglyoxal-bis(guanylhydrazone) (MGBG) as part of Phase I studies. Five patients included in the trial exhibited morphologic evidence of cellular differentiation during the course of treatment. In one patient who exhibited no blasts and a normal white blood cell differential at the end of treatment the mononuclear cell content of all three polyamines declined after an initial increase in spermidine and spermine content. In the other patients in whom the cellular maturation was less pronounced the mononuclear cell polyamine levels remained stable or increased over the treatment time. No absolute difference was apparent between the cellular polyamine levels detected in patients at the times of the greatest increase in per cent circulating neutrophils as compared to the cellular levels present in patients whose circulating mononuclear cell number were increasing. Circulating mononuclear cell putrescine, spermidine, and spermine levels varied over two orders of magnitude from patient to patient and the range of values detected in each state completely overlapped those present in the other. It does not appear from the present study that there is a consistent human leukemic cell polyamine content at which cellular differentiation occurs.

Adolescent↗
PubMed1989

Immunolocalization of ornithine decarboxylase in rat heart atria.

Mammalian atrial myocytes secrete a potent natriuretic and diuretic factor, atrial natriuretic peptide (ANP), in response to volume expansion or elevations of right atrial pressure. ANP is synthesized in the atrial atrial myocytes and stored in cytoplasmic secretory granules. Ornithine decarboxylase (ODC) is the initial rate-limiting enzyme in the biosynthesis of polyamines, organic cations which are essential for various aspects of DNA, RNA and protein synthesis, structure, and function. The enzyme has been reported to be localized predominantly in the cytoplasm. A polyclonal antibody elicited against ODC was used to analyse the intracellular distribution of the enzyme protein within atrial myocytes at the ultrastructural level through the use of a post-embedding immunogold technique. In control animals, the density of gold particles associated with the atrial granules was seven to 30-fold higher than that detected in association with other subcellular structures. Administration of Isoproterenol increased atrial of Isoproterenol increased atrial ODC activity 18-fold and the density of the immunolabelling of the atrial myocytes five-fold. Statistically significant increases in the density of labelling after stimulation occurred in association with the atrial granules and the nucleus. After isoproterenol stimulation, 60% of the immunodetectable ODC protein in the atrial myocyte was found in association with the atrial granules. The atrial granules were demonstrated to contain ANP by immunocytochemical analysis of adjacent sections.

Animals↗
PubMed1989

Mucosal ornithine decarboxylase in the small intestine: localization and stimulation.

In most tissues increases in ornithine decarboxylase (ODC) are associated with growth. Refeeding fasted rats. a potent stimulus for mucosal growth, strongly increases ODC in both small and large intestinal mucosa. In the small bowel, almost all of this increase occurs in the mature villus cells rather than the proliferative crypt cells. Nevertheless, inhibition of ODC with difluoromethylornithine blocks the growth response. Using a highly specific, polyclonal antiserum to ODC, we have determined that in the fasted rat ODC is localized almost exclusively to the villus cells. Using antiserum dilution techniques, we have shown that, within 2 h, refeeding increases the amount of immunoreactive ODC in both villus and crypt cells. Furthermore, the trophic hormone gastrin also increases ODC, but only in the crypt cells. Epidermal growth factor increased ODC to a greater extent than gastrin, but stimulation was more general, including both crypt and villus cells. Perfusing an isolated segment of small bowel in situ with glycine for 2 h also increased immunoreactive ODC but only in the villus cells. Thus in the small intestine the effect of refeeding on ODC activity appears to be mediated by different types of stimuli: luminal nutrients increase enzyme levels in the absorbing villus cells, while trophic peptides stimulate ODC synthesis in the proliferative crypt cells.

Animals↗
PubMed1989

Characterization of casein kinase II from a virally transformed macrophage-like cell line, RAW264.

Casein kinase II from a virally-transformed macrophage cell line (RAW264) was purified by a sequential DEAE, Procion Red, phosvitin-Sepharose and heparin-Sepharose chromatography. With [tau-32P]GTP as a phosphate donor and casein as a substrate, the kinase was stimulated by polyamines and inhibited by heparin. The purified kinase had a specific activity of 1137 nmol/min/mg protein and exhibited three major protein bands of 40 K, 35 K, and 25 K. Under non-denaturing conditions in 50 mM Tris-50 mM NaCl the enzyme was eluted as a single peak with molecular weight of 110 K. Incubation of kinase in the presence of [tau-32P]GTP and Mg2+ resulted in phosphorylation of the 25 K protein band of the enzyme. In the presence of [tau-32P]GTP and Mg2+ the kinase was able to phosphorylate 55 K protein band in purified ornithine decarboxylase preparation from RAW264 cells and the rat-type II regulatory subunit of the cyclic AMP-dependent protein kinase.

Animals↗
PubMed1988

Alterations in bone marrow and blood mononuclear cell polyamine and methylglyoxal bis(guanylhydrazone) levels: phase I evaluation of alpha-difluoromethylornithine and methylglyoxal bis(guanylhydrazone) treatment of human hematological malignancies.

Nine patients with hematological malignancies were treated with difluoromethylornithine and methylglyoxal bis(guanylhydrazone). The number of circulating blast cells decreased in all of the patients treated with DFMO and MGBG for longer than 1 wk. Morphological evidence of myeloid maturation was evident in four patients with leukemia and the circulating M Protein decreased in one patient with multiple myeloma. The polyamine content of the mononuclear cells in both the peripheral blood and bone marrow was transiently increased after the initial MGBG dose. During administration of DFMO decreases were achieved in the peripheral blood mononuclear cell putrescine levels in 7 patients, spermidine levels in 5 patients, and spermine levels in 4 patients. Alterations in bone marrow mononuclear cell polyamine levels were similar to those which occurred in the peripheral cells. An average of 9 days of DFMO treatment was required to lower mononuclear cell polyamine levels. Three of the 4 evaluable patients receiving multiple MGBG doses had an increased mononuclear cell content of MGBG after DFMO pretreatment. Enhancement of cellular MGBG levels was not directly correlated to the degree of cellular polyamine depletion.

Adult↗
PubMed1988

Alterations in human circulating and bone marrow mononuclear cell polyamine levels in hematologic malignancies as a consequence of difluoromethylornithine administration.

The effect of administering increasing intravenous doses of difluoromethylornithine on human tumor cell polyamine levels was determined in patients with hematologic malignancies. Difluoromethylornithine from 5.5. to 64 gm/m2 per day was administered to nine patients with refractory acute leukemia or multiple myeloma. Putrescine, spermidine, and spermine levels were determined on a daily basis in the circulating mononuclear cells and on a weekly basis in the mononuclear cells of the bone marrow. Tumor cell putrescine levels declined in 5 patients, spermidine levels declined in 4 patients, and spermine levels declined in 3 patients. Alterations in the polyamine levels of the bone marrow mononuclear cells paralleled those occurring in the peripheral blood mononuclear cells in the patients with leukemia. Seven to ten days of DFMO treatment were required for mononuclear cell polyamine levels to decrease. The higher drug doses were not significantly more effective than the lower doses in bringing about a decline in tumor cell polyamine levels, either with respect to treatment time required for onset of response or with respect to the ultimate extent of response.

Adolescent↗
PubMed1988

Gastric mucosal ornithine decarboxylase: localization and stimulation by gastrin.

Gastrin injection and refeeding fasted rats are effective trophic stimuli for the oxyntic gland mucosa of the stomach. Neither stimulus increases detectable ornithine decarboxylase (ODC) activity in the tissue. Difluoromethylornithine (DFMO), a potent inhibitor of ODC, blocks the mucosal growth response, indicating that ODC activity is necessary for growth. Elevated levels of spermidine and spermine are detectable in the mucosa after gastrin administration. Using a highly specific, polyclonal antiserum to ODC, we determined that the enzyme is present in oxyntic gland mucosa confined to a narrow band of cells at the base of the gastric pits and openings of the glands. In antral mucosa, ODC is present throughout the lower 20% of the mucosa, which consists of the necks and pyloric glands. Using antiserum dilution techniques, we show that gastrin administration increases immunoreactive ODC in the oxyntic gland area but not in the antral mucosa, where it has no trophic effect. Elevated cellular content of ODC is apparent within 2 h after injection of gastrin, peaks at 4 h, and declines to basal levels by 12 h. Gastrin-stimulated increase in ODC is confined to the narrow band of cells in which low levels of the enzyme protein were detected in control animals. The decarboxylating activity detectable in oxyntic gland mucosal extracts is not inhibited by administration of DFMO or cycloheximide, each of which inhibits ODC activity in other tissues. Addition of unlabeled lysine to the decarboxylation assay reaction of oxyntic gland mucosa extract inhibits the decarboxylation of radiolabeled ornithine substrate. Thus it is likely that the stomach possesses nonspecific decarboxylase activity, which accounts for most of the measured activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Characteristics of cyclic AMP enhancement of retinoic acid induction of increased transglutaminase activity in HL60 cells.

When the human myeloid leukemia cell line (HL60) is induced to differentiate with retinoic acid (RA), there is a concentration-dependent increase in transglutaminase (TGase) activity which peaks on day 5. While dibutyryl 3',5'-cyclic adenosine monophosphate (db-cAMP) alone produced only a slight increase in TGase activity in HL60 cells, the concomitant addition of db-cAMP (100 microM) with RA (10(-12)-10(-4) M) potentiates RA induction of TGase activity. Maximal increases in TGase activity (2- to 10-fold) were observed with 10(-4)-10(-7) M RA and when db-cAMP was present from 24 to 48 h after the addition of RA. The cyclic nucleotide enhancement was dose-dependent from 10 to 100 microM of cAMP. Less marked increases were observed with 8-bromo-cAMP and with the phosphodiesterase inhibitor theophylline. Although the simultaneous addition of PGE1 or PGE2 (10(-8)-10(-6) M) produced no enhancement of RA-induced TGase activity, adding PGE1 or PGE2 24 or 48 h following RA treatments produced an enhancement of TGase activity. The phosphodiesterase inhibitor potentiated the increases produced by db-cAMP and the prostaglandins. Dibutyryl cAMP enhanced the ability of RA to induce the cells to reduce nitroblue tetrazolium (NBT), a functional measure of differentiation, at lower concentrations of RA and with shorter treatment durations. cAMP potentiates RA-induced TGase activity in HL60 cells and the combination appears to be associated with enhanced RA-induced differentiation.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1988

Polyamines increase in human peripheral blood and bone marrow mononuclear cells following administration of methylglyoxal bis(guanylhydrazone).

Eight patients who had refractory leukemia and 1 patient with refractory multiple myeloma were treated with the polyamine biosynthesis inhibitors methylgloxal bis(guanylhydrazone) (MGBG) and difluoromethylornithine (DFMO). After the first dose of MGBG there was an increase in polyamine content in the mononuclear cells of both the peripheral blood and the bone marrow despite the administration of DFMO in all patients with leukemia. Putrescine levels increased in the mononuclear cells of all patients, cellular spermidine levels increased in 4 and cellular spermine levels increased in 5 patients. The cellular polyamine levels remained elevated above the pretreatment levels for up to 1 week in some patients. Subsequent treatment with MGBG, administered after 1-2 weeks of DFMO treatment, also promoted increases in mononuclear cell polyamine concentrations. Since enhanced tumor cell uptake of MGBG after DFMO priming is hypothesized to be dependent on a decrease in cellular polyamine levels, the increase in cellular polyamines after MGBG has important implications for the scheduling of this drug combination. From these observations, withholding MGBG until DFMO treatment has produced a decrease in tumor cell polyamine concentrations would be the schedule most likely to enhance the uptake of MGBG.

Adult↗
PubMed1988

Prostaglandin-mediated trophic effects on the rat duodenum: the role of polyamines.

Ornithine decarboxylase (ODC) is the initial rate-limiting enzyme in polyamine biosynthesis. The relationship between ODC and polyamines and the trophic effect of prostaglandin in the rat gastrointestinal tract are unknown. In these studies we determined whether inhibition of ODC activity and subsequent polyamine biosynthesis with the specific enzyme inhibitor difluoromethyornithine (DFMO) would attenuate prostaglandin-mediated trophic effects in the rat duodenum. Significant increases in duodenal mucosal wet weight, RNA, DNA, and protein were found following treatment with 16,16-dimethyl-PGE2 (1 mg/kg) for 1 week. This trophic response was significantly reduced (P less than 0.01) in the duodenum of rats treated concomitantly with DFMO. In addition, this prostenoid significantly increased (4X) duodenal ODC levels, 2 hr following acute administration. These results suggest that polyamines are required for the prostaglandin-stimulated growth of the rat duodenal mucosa.

16,16-Dimethylprostaglandin E2↗
PubMed1987

Difluoromethylornithine enhances the uptake of methylglyoxal-bis(guanylhydrazone) prior to inhibiting leukemic cell proliferation.

Difluoromethylornithine (DFMO) is a nonreversible inhibitor of ornithine decarboxylase (ODC), the initial rate-limiting enzyme in the polyamine biosynthetic pathway. When HL60 leukemic cells were incubated in the presence of concentrations of DFMO from 0.05 mM to 5 mM, there was a concentration-dependent inhibition of ODC activity apparent within 24 h. Likewise, cellular polyamine levels were reduced by the presence of DFMO in a concentration-dependent manner after 4 days. The growth of cells incubated with 0.5 mM or greater was inhibited after 3-4 cell doublings. When the concentration of DFMO was less than 0.5 mM, growth was not inhibited. Methylglyoxal-bis(guanylhydrazone) (MGBG) uptake was enhanced in cells treated with concentrations of 0.05-0.5 mM DFMO, but not enhanced in cells treated with DFMO concentrations of 1 mM or greater. DFMO-induced cellular polyamine depletion does enhance MGBG uptake into HL60 cells, but treatment with high concentrations of DFMO, which deplete polyamines to the extent that growth is inhibited, negate this effect.

Cell Division↗
PubMed1986

Immunocytochemical localization of ornithine decarboxylase in cultured murine cells.

Antiserum elicited to ornithine decarboxylase (ODC) purified from murine RAW 264 macrophage-like cells has been employed to localize ODC in cultured murine cells. The antiserum immunoprecipitated 100% of the ODC activity from the cultured cells. The specificity of the antiserum was demonstrated by the immunoprecipitation from 35S-methionine metabolically-labeled cell extracts of a single protein which migrated upon SDS-gel electrophoresis coincident with authentic ODC. Indirect immunofluorescence experiments were performed on paraformaldehyde-fixed RAW 264 cells and JB6 epidermal cells using the rabbit anti-ODC antiserum and FITC-conjugated goat anti-rabbit IgG. Little immunofluorescence was apparent in non-stimulated cells. Intense immunofluorescence was detectable in stimulated cells at times of peak cellular ODC activity. Antigenically-reactive ODC was localized diffusely in the cytoplasm and was absent in the nuclei of RAW 264 cells, whereas in the JB6 cells the immunodetectable enzyme protein was localized in a punctate pattern in both the cytoplasm and nucleoplasm and was absent in the nucleolus. The appearance and disappearance of immunoreactive ODC in both cell types after stimulation was consistent with the alterations in ODC activity.

Animals↗
PubMed1986

Effect of refeeding on polyamine biosynthesis in isolated enterocytes.

Ornithine decarboxylase (ODC) activity has been found to be preferentially associated with small intestinal villus cells rather than crypt cells in the rat. In the present study, ODC, S-adenosylmethionine decarboxylase (SAMDC), and polyamines were measured in isolated enterocytes to determine which cell populations increased polyamine biosynthetic activity after refeeding. Two hours following refeeding, significant increases in ODC were observed in villus tip (10 times) and midvillus (20 times) enterocytes. No increase in ODC activity was found in isolated crypt cells. A similar pattern was observed for SAMDC. Enzyme activity increased in villus tip (2 times) and midvillus (27 times) cells but not in crypt enterocytes. Putrescine contents were increased following refeeding in midvillus enterocytes (P less than 0.05) and in crypt cells (P less than 0.05). The accumulation of putrescine in midvillus cells occurs via ODC-induced biosynthesis, whereas in crypt enterocytes it may be due to putrescine uptake. The lack of induction of ODC and SAMDC in crypt enterocytes following acute refeeding suggests these enzymes are apparently not involved in the initiation of cell proliferation known to occur under this condition.

Adenosylmethionine Decarboxylase↗
PubMed1985

Bacterial lipopolysaccharide induction of ornithine decarboxylase in the macrophage-like cell line RAW264: requirement of an inducible soluble factor.

Ornithine decarboxylase (ODC, EC 4.1.1.17) activity is induced in the RAW264 macrophage-like cell line by bacterial lipopolysaccharide (LPS). As little as 0.1 ng/ml LPS promoted an increase in ODC activity, while maximal ODC activity (30-fold above control) was induced with 1.0 microgram/ml LPS. An increase in ODC activity was detectable within 90 min of LPS addition. The LPS-induced increase in ODC activity was prevented by inhibitors of protein and RNA synthesis. The induction of the enzyme by LPS was not dependent on prostaglandin production. However, PGE2 (1 microgram/ml) and 8-bromo-cyclic AMP (1 mM), neither of which had an effect on ODC activity when added alone, each acted synergistically to enhance the LPS induction of ODC activity. Enzyme induction was not associated with an alteration in Km for ornithine, which remained constant at 0.04 mM. The extent of the increase in ODC in response to LPS increased with increasing cellular density. This relationship was dependent not on absolute cell density of the monolayer but on the cell number in relation to medium volume, and this dependence could be extrapolated to the origin. Addition of conditioned media from LPS-stimulated but not unstimulated cultures enhanced the ODC increase in sparsely plated cultures in response to a maximal concentration of LPS. The addition of polymyxin B, a reagent that blocks the effects of LPS, including the increase in ODC activity, did not totally inhibit the conditioned medium stimulation. This data indicates that two signals, LPS and a LPS-induced mediator, are involved in the induction of ODC activity in RAW264 cells.

Animals↗
PubMed1985

Localization of ornithine decarboxylase in rat testicular cells and epididymal spermatozoa.

We have employed a monospecific, polyclonal antibody to ornithine decarboxylase (ODC) for the immunocytochemical localization of ODC in freshly isolated testicular cells, epididymal spermatozoa, and cultured Sertoli cells. Antigenically detectable material was present in the cytoplasm of all cell types tested and was highly concentrated in the acrosomal vesicle of round spermatids and in the acrosome region of epididymal spermatozoa. The specific enzymatic activity of ODC, as measured biochemically, was much higher in the interstitial cells than in the other testicular cell types, and no ODC activity was detected in the epididymal spermatozoa or in the Sertoli cells after 5 days in culture. These studies showed that, while all testicular cell types studied contained ODC-like immunoreactive molecules, only testicular germ cells and interstitial cells exhibited detectable ODC activity.

Animals↗