Reversal of doxorubicin, etoposide, vinblastine, and taxol resistance in multidrug resistant human sarcoma cells by a polymer of spermine

We have previously described the synthesis of a cytotoxic polymeric conjugate of spermine (Poly-SPM) which is able to inhibit the transport of polyamines (spermine, spermidine, and putrescine) into normal and malignant cells. Recent studies examining the toxicity of Poly-SPM in parental and multidrug resistant (MDR) cancer cells have revealed a cross-resistance in the MDR variant Dx5 to the toxic effects of the conjugate in the MDR-positive cells. There were also differences in spermine and putrescine uptake rates between parental and MDR-positive with the MDR-positive cells having a lower Vmax and a higher Km. The ability of this Poly-SPM to reverse MDR was examined in MDR variants (Dx5 cells) of the human sarcoma cell line MES-SA. The cells express high levels of the mdr1 gene product, P-glycoprotein, and are 25-to 60-fold resistant to doxorubicin (DOX), etoposide (VP-16), vinblastine (VBL), and taxol (TAX). Cytotoxicity was measured by the MTT [3-(4,5-dimethyldiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay. Poly-SPM (50 microM) lowered the drug concentration IC50 values in the Dx5 cells by 37-fold with VBL, 42-fold with DOX, 29-fold with VP-16, and 25-fold with TAX when compared to the control IC50 values without Poly-SPM. This reversal of resistance was concentration dependent, decreasing 17-fold with DOX, 6.1-fold with VBL, 19-fold with VP-16, and 5-fold with TAX when 25 microM Poly-SPM was used. No modulation was observed in the parental cell line MES-SA, which does not express the mdr1 gene. Poly-SPM had no influence on the IC50 of non-MDR chemotherapeutic agents such as cisplatin. The modulation studies correlated with the ability of Poly-SPM to reverse the cellular accumulation defect of [3H]-VBL and [3H]-TAX in the Dx5 but not MES-SA cells. Pretreatment of the Dx5 cell with alpha-difluoromethylornithine (DFMO at 2 and 5 microM) for 24 h increased the function of the MDR transporter to further decrease the cellular accumulation of VBL and TAX when compared to untreated cells. DFMO pretreatment is known to upregulate the polyamine transporter(s). These findings show that, in addition to inhibiting polyamine transport, Poly-SPM reverses MDR in Dx5 cells, suggesting a potential relationship between the polyamine influx transporter and the MDR efflux pump. This potential functional link between the polyamine influx transporter(s) and the MDR efflux transporter (P-glycoprotein) offers a novel approach to inhibiting this form of drug resistance.

Temperature-dependent regulation of Yersinia enterocolitica Class III flagellar genes

Temperature is a key environmental cue for Yersinia enterocolitica as well as for the two other closely related pathogens, Yersinia pestis and Yersinia pseudotuberculosis. Between the range of 30 degrees C and 37 degrees C, Y. enterocolitica phase-varies between motility and plasmid-encoded virulence gene expression. To determine how temperature regulates Y. enterocolitica motility, we have been dissecting the flagellar regulatory hierarchy to determine at which level motility is blocked by elevated temperature (37 degrees C). Here we report the cloning, DNA sequences, and regulation of the two main regulators of Class III flagellar genes, fliA (sigma F) and flgM (anti-sigma F), and a third gene, flgN, which we show is required for filament assembly. Identification of the Y. enterocolitica fliA and flgM genes was accomplished by functional complementation of both S. typhimurium and Y. enterocolitica mutations and by DNA sequence analysis. The Y. enterocolitica fliA gene, encoding the flagellar-specific sigma-factor, sigma F, maps immediately downstream of the three flagellin structural genes. The flgM and flgN genes, encoding anti-sigma F and a gene product required for filament assembly, respectively, map downstream of the invasin (inv) gene but are transcribed in the opposite (convergent) direction. By using Northern blot analyses we show that transcription of both fliA and flgM is immediately arrested when cells are exposed to 37 degrees C, coincident with the timing of virulence gene induction. Unlike S. typhimurium flgM mutants, Y. enterocolitica flgM mutants are fully virulent.

A novel polymeric spermine conjugate inhibits polyamine transport in pulmonary artery smooth muscle cells

The polyamines putrescine, spermidine and spermine (SPM) are low molecular weight organic cations that play essential intracellular regulatory roles in cell growth and differentiation. Whereas both de novo polyamine synthesis and transmembrane transport regulate cell polyamine contents, exploitation of pathways as pharmacologic targets has been limited by the lack of agents which specifically block polyamine transport. We now report the synthesis and biologic activity of novel polymeric glutaraldehyde conjugates of putrescine, spermidine and SPM which act at the cell membrane to inhibit polyamine uptake in cultured bovine pulmonary artery smooth muscle cells. Each conjugate caused dose-related inhibition of [14C]polyamine transport in pulmonary artery smooth muscle cells with the polymeric SPM conjugate being most effective in inhibiting the uptake of all three polyamines. Polymeric SPM failed to impair uptake of neutral or charged amino acids or to associate with pulmonary artery smooth muscle cells in a temperature-dependent manner. The polymeric SPM conjugate caused substantial decreases in cell polyamine contents which were associated with concentration-dependent cytotoxicity. Spectroscopic analyses of the polymeric SPM conjugate indicated that its molecular weight was 25 +/- 0.5 kDa, which is equivalent to approximately 90 monomeric--HN(CH2)3NH(CH2)4NH(CH2)3NH(CH2)5--units. These findings indicate that reduced polymeric glutaraldehyde conjugates of the polyamines may function as specific inhibitors of polyamine transport and thus provide a basis for examination of polyamine transport as a pharmacologic target in disorders characterized by dysregulated cell growth and differentiation.

HypB protein of Bradyrhizobium japonicum is a metal-binding GTPase capable of binding 18 divalent nickel ions per dimer

Bradyrhizobium japonicum hypB encodes a protein containing an extremely histidine-rich region (24 histidine residues within a 39-amino-acid stretch) and guanine nucleotide-binding domains. The product of the hypB gene was overexpressed in Escherichia coli and purified by Ni(2+)-charged metal chelate affinity chromatography (MCAC) in a single step. In SDS/PAGE, HypB migrated at 38 kDa--slightly larger than the calculated molecular mass (32.8 kDa). Purified HypB has GTPase activity with a kcat of 0.18 min-1 and a Km for GTP of 7 microM, and it has dGTPase activity as well. HypB exists as a dimer of molecular mass 78 kDa in native solution as determined by fast protein liquid chromatography on Superose 12. It binds 9.0 +/- 0.14 divalent nickel ions per monomer (18 Ni2+ per dimer) with a Kd of 2.3 microM; it also binds Zn2+, Cu2+, Co2+, Cd2+, and Mn2+. In-frame deletion of the histidine-rich region (deletion of 38 amino acids including 23 histidine residues) resulted in a truncated HypB that did not bind to the MCAC column, whereas in-frame deletion of 14 amino acids including 8 histidine residues within HypB resulted in a truncated HypB that still bound to the column. The results indicate that the histidine residues within the histidine-rich region of HypB are involved in metal binding.

Basic fibroblast growth factor alterations during development of monocrotaline-induced pulmonary hypertension in rats

The chemical signaling pathways which orchestrate lung cell responses in hypertensive pulmonary vascular disease are poorly understood. The present study examined temporal alterations in lung basic Fibroblast Growth Factor (bFGF) in a well characterized rat model of monocrotaline (MCT)-induced pulmonary hypertension. By immunohistochemical analysis, there were progressive increases in bFGF in airway, vascular and gas exchange regions of MCT-treated rat lungs. Increases in bFGF preceded the onset of right ventricular hypertrophy at day 21 after MCT administration. Enhanced bFGF immunostaining was observed as early as day 4 in focal areas of the parenchyma, and by day 14 there was enhanced bFGF staining in alveolar macrophages, neutrophils and alveolar septa, which persisted through day 21. In conducting airways, there was elevated bFGF immunostaining in the smooth muscle cell (SMC) layer by days 4 and 7 and in the ciliated epithelium and its basement membrane at days 14 and 21. Cells morphologically similar to Clara cells in the luminal surfaces of bronchioles stained intensely on days 14 and 21. In the nucleus and cytoplasm of medial SMCs within pulmonary arteries, there was a progressive increase in bFGF staining starting at day 4. Lung bFGF mRNA was increased slightly at days 1, 4 and 7, while lung bFGF protein, as judged by western blot analysis, was increased at days 14 and 21 compared to controls. The present results, considered in teh light of teh documented roles of bFGF in vascular cell migration, growth and synthesis of extracellular matrix components, suggest that bFGF may contribute to the structural remodeling processes underlying the development of chronic pulmonary hypertension in MCT-treated rats.

Monocrotaline alters type II pneumocyte morphology and polyamine regulation

Lungs from monocrotaline (MCT)-treated rats exhibit altered polyamine metabolism and content. One of the prominent morphological abnormalities in MCT-treated lungs is a decrease in population density of type II pneumocytes. Against this background, the present study tested the hypothesis that failure to maintain normal population density of type II pneumocytes is associated with MCT-induced derangements in polyamine biosynthesis and/or transmembrane polyamine transport. After a 24-hr treatment, cultured type II pneumocytes exhibited numerous vacuoles at the highest dose of 3.2 mM MCT but not at the lower dose of 1.6 mM MCT. Intracellular spermidine content was significantly reduced at the highest dose of MCT. Relative to controls, the abundance of mRNA for both ornithine decarboxylase, and S-adenosylmethionine decarboxylase, key regulatory enzymes in polyamine synthesis, was not altered. However, the activities of both of these enzymes were dramatically reduced. Increased mRNA for the catabolic polyamine enzyme, spermine/spermidine-N1-acetyltransferase (SAT), paralleled significant increases in SAT activity. MCT also caused a concentration-related inhibition of spermidine uptake in type II cells, characterized by a fourfold decrease in Vmax with little change in Km. These results show that MCT alters type II pneumocyte polyamine regulatory mechanisms and may help explain the decreased population density of type II pneumocytes in MCT-treated rats.

Role of ATP and sodium in polyamine transport in bovine pulmonary artery smooth cells

Increased polyamine transport may be a key mechanism driving elevations in lung cell polyamine content necessary for the development of chronic hypoxic pulmonary hypertension. Bovine pulmonary artery smooth muscle cells (PASMCs) in culture exhibit two carriers for polyamines, a non-selective one shared by the three polyamines, putrescine (PUT), spermidine (SPD), and spermine (SPM), and another that is selective for SPD and SPM. Hypoxia appears to up-regulate both carriers. In this study, we examined the role of ATP and the Na+ gradient in regulating polyamine transport in control PASMCs and in PASMCs with polyamine transport augmented by culture under hypoxic conditions (Po2: 15-30 torr). Inhibition of ATP synthesis with dinitrophenol+iodoacetate profoundly reduced polyamine uptake in both control and hypoxic PASMCs. Putrescine uptake was somewhat more sensitive to iso-osmotic replacement of extracellular Na+ with choline chloride or sucrose than were SPD or SPM in both hypoxic and standard cells, but under no conditions did Na+ replacement substantially alter polyamine uptake. Treatment of PASMCs with ouabain, a Na(+)-K+ ATPase inhibitor, or with gramicidin, a Na+ ionophore, minimally attenuated polyamine transport, whereas the Na+/K+ ionophore monensin increased polyamine uptake in standard, but not in hypoxic, cells. In general, the reduction in the extracellular Na+ content or ionophore-induced increases in Na+ permeability had a greater suppressive effect on polyamine transport in hypoxic cells than in standard cells, suggestive of the induction of Na(+)-dependent polyamine carriers by hypoxia. These observations indicate that the activities of the two putative polyamine transport pathways in standard PASMCs, as well as their up-regulation by hypoxia, require ATP synthesis. In addition, it appears that polyamine transport in PASMCs is composed of two components: one a prominent sodium-independent transporter and the other a relatively minor component that is sodium dependent. The latter may be activated by hypoxic exposure in combination with the induction of new polyamine carriers.

Eflornithine treatment in SHR: potential role of vascular polyamines and ornithine decarboxylase in hypertension

This study was performed to assess the potential role of polyamines in the alterations in vascular structure and function in spontaneously hypertensive rats (SHR). The effects of chronic administration of eflornithine (alpha-difluoromethylornithine; DFMO), a highly specific inhibitor of ornithine decarboxylase (the rate limiting enzyme in polyamine biosynthesis), on vascular polyamine contents, vascular structure and function, and blood pressure was studied. Male SHR (16-17 weeks of age) with an average systolic blood pressure (SBP) of 161 +/- 3 mmHg were used. The rats were divided into two groups and received either tap water or a 1% DFMO solution to drink for 6 weeks. SBP and body weight were recorded prior to and once-a-week during the experiment. Standard in vitro vascular reactivity studies on ring segments of aorta and tail artery were performed. Ring segment weight, arterial medial thickness, and vascular polyamine contents were also determined. Body weights were not significantly affected by the DFMO treatment. SBP in control SHR rose progressively to an average value of 185 +/- 5 mmHg by the sixth experimental week. Although DFMO treatment did not cause a significant decrease in SBP compared to pretreatment values, it did prevent a further increase in SBP. Aortic and tail artery responsiveness to norepinephrine and electrical stimulation, respectively, ring segment weight, arterial medial thickness, and vascular polyamine contents were all significantly less in SHR receiving the DFMO treatment. These data are the first to demonstrate the effectiveness of DFMO to lower polyamine contents in the vasculature of hypertensive SHR.(ABSTRACT TRUNCATED AT 250 WORDS)

Surfactant disposition in rats with monocrotaline-induced pneumotoxicity

Monocrotaline (MCT)-treated rats exhibit airways and gas exchange abnormalities which precede development of sustained pulmonary hypertension (Lai et al., 1991). Because the density of type II pneumocytes is reduced in MCT-treated rat lungs (Wilson and Segall, 1990), decreased abundance or activity of type II pneumocyte-derived surfactant may contribute to pulmonary dysfunction. On the other hand, since the remaining type II pneumocytes undergo an apparent hypertrophic response, it is possible that they compensate for the reduction in population density by elaborating more surfactant or surfactant with enhanced surface activity. As an initial means of discriminating between these possibilities, the amount, surface activity, and synthesis rate of surfactant was examined in rats at 1, 2, and 3 weeks after MCT administration. The amounts of surfactant phospholipid and protein recovered in bronchoalveolar lavage fluid did not differ substantially between control and MCT-treated rats at any time post MCT administration. Similarly, neither the initial rate of surface tension reduction nor the maximum reduction in surface tension differed between surfactant preparations recovered from control and MCT-treated rats. The rate of surfactant synthesis in lung explants, as determined by incorporation of [3H]glycerol into phospholipid, also was not different between MCT-treated and control rats at any time after MCT administration. MCT treatment failed to alter the distribution of [3H]glycerol into surfactant phospholipid. Collectively, these data indicate that airways abnormalities in MCT-treated rats cannot be ascribed to a reduction in the abundance or the activity of surfactant. Furthermore, in light of previous studies indicating that the density of type II pneumocytes is reduced in MCT pneumotoxicity, the present findings suggest that surfactant regulatory pathways must undergo a compensatory response that preserves normal functional status.

Multiple polyamine transport pathways in cultured pulmonary artery smooth muscle cells: regulation by hypoxia

The polyamines putrescine (PUT), spermidine (SPD), and spermine (SPM) are a family of low molecular weight organic cations that play essential intracellular regulatory roles in cell growth and differentiation. Consistent with this important function, increases in cellular polyamine contents are necessary for a variety of physiologic and pathologic events in the lung, including development of hypertensive pulmonary vascular disease secondary to chronic alveolar hypoxia. In intact rat lungs, hypoxia depresses ornithine decarboxylase activity, the initial rate-limiting enzyme in de novo polyamine synthesis, and enhances uptake of PUT from the vascular compartment, thus suggesting that increased polyamine transport is the driving mechanism behind hypoxia-induced increases in lung polyamine contents. Cultured bovine pulmonary artery smooth muscle cells (PASMCs) also express a transport system for SPD that is augmented by culture under hypoxic conditions. Because there may be multiple uptake pathways that are relatively selective for specific polyamines, the present study determined whether cultured bovine PASMCs expressed discrete transporters for [14C]PUT, [14C]SPD, and [14C]SPM, and whether they were differentially regulated by hypoxia. [14C]PUT, [14C]SPD, and [14C]SPM transport was examined in PASMCs cultured under "standard" (culture medium PO2: > 100 torr), "normoxic" (culture medium PO2: 50 to 70 torr), or "hypoxic" (culture medium PO2: 18 to 30 torr) conditions. Uptake of all three [14C]polyamines in cells cultured under standard conditions was temperature- and concentration-dependent, exhibited saturation kinetics, and could be modeled by Michaelis-Menten kinetics. In hypoxic PASMCs, values of Vmax for PUT, SPD, and SPM uptake increased by 3-, 2-, and 2-fold, respectively, relative to cells cultured under normoxic or standard incubator conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Temporal alterations in specific basement membrane components in lungs from monocrotaline-treated rats

The present study utilized the monocrotaline (MCT) model of pulmonary hypertension in rats to examine temporal alterations in steady-state levels of basement membrane (BM) component mRNA and deposition of protein using Northern analysis and immunohistochemistry, respectively. MCT (60 mg/kg, subcutaneous) produced sustained increases in lung dry tissue mass by 7 days, right ventricular mass by 14 days, and pulmonary arterial pressure by 21 days after administration. mRNA levels specific for laminin (LM) were elevated as early as 1 day after MCT treatment, while mRNA for all BM components examined except type IV collagen were increased in lungs from MCT-treated rats by day 4. Differences in LM, perlecan (PN), and type IV collagen-specific mRNAs from lung tissue between MCT-treated and control rats disappeared by day 14. In contrast, fibronectin (FN) mRNA remained elevated in lung tissue from MCT-treated rats from day 4 onward. Increases in immunolocalizable FN and LM in the vasculature, and PN and type IV collagen in gas exchange areas, were observed 4 days after MCT treatment compared with controls. These changes generally became more pronounced by 21 days after MCT administration, at which time the parenchyma of MCT-treated rats also demonstrated increases in immunolocalizable FN, LM, and BM-chondroitin sulfate proteoglycan (BM-CSPG). The pulmonary vasculature additionally showed increases in type IV collagen, PN, and BM-CSPG in MCT-treated rats compared with controls by 21 days. These observations suggest that the accumulation of specific BM components in the pulmonary vasculature and parenchyma may contribute to the pathogenesis and maintenance of MCT-induced hypertensive pulmonary vascular disease.

Alterations of growth factor transcripts in rat lungs during development of monocrotaline-induced pulmonary hypertension

Although pathologic and hemodynamic changes in monocrotaline (MCT)-induced pulmonary hypertension have been studied extensively, relatively little is known about the inter- and intracellular signaling mechanisms underlying such alterations. As a first step to delineating signaling mechanisms governing adverse structural alterations in the hypertensive lungs, we examined changes in the steady-state levels of mRNAs encoding several growth factors including transforming growth factors (TGF), platelet-derived growth factors (PDGF), vascular endothelial cell growth factor (VEGF) and endothelin (ET) as a function of time in MCT-induced pulmonary hypertension in rats. These studies demonstrated a very diverse pattern of growth factor gene expression in response to MCT administration. In general, alterations in the steady-state levels of mRNAs encoding the growth factors preceded the onset of MCT-induced pulmonary hypertension. TGF-beta 1, -beta 2 and -beta 3 transcripts were seen to be elevated, whereas that of TGF-alpha and PDGF-A remained unchanged. Transcripts for PDGF-B and ET were increased in the early stages but declined to less than controls in the latter stages of MCT-induced hypertension. In contrast, levels of VEGF mRNA decreased to less than controls as the disease progressed. Viewed collectively, the diverse pattern of expression suggests that alterations in the levels of the growth factor transcripts may have a significant role in the development of pulmonary hypertensive disease and may be relevant to the pathological and structural changes in MCT-induced pulmonary hypertension.

Expression of polyamine transporter activity during B lymphocyte cell cycle progression

The movement of resting B cells into the early stages of the cell cycle is accompanied by elevations in cellular polyamine levels. Our previous results indicate that part of this increase is a consequence of enhanced levels of ornithine decarboxylase activity in activated B cells. However, the levels of ornithine decarboxylase wane within 30 h post-stimulation, suggesting that B cells may acquire polyamines from an alternative source. Results in the present communication indicate that B cells initiate the transport of extracellular polyamines as they enter the G1 stage of the cell cycle. This induction of polyamine transport activity is seen after the stimulation of B cell cycle progression by both PMA and ionomycin, as well as cognate help from activated Th cells. The transport activities are energy and temperature sensitive, and can be competitively inhibited by unlabeled ligands. The results of the competition studies are compatible with the presence of at least two types of transporters, a low affinity transporter for both putrescine and spermidine, and a higher affinity transporter selective for spermidine. The results are discussed in terms of biochemical events associated with Th cell-mediated, B cell activation.

Expression of polyamine transporter activity during B lymphocyte cell cycle progression

The movement of resting B cells into the early stages of the cell cycle is accompanied by elevations in cellular polyamine levels. Our previous results indicate that part of this increase is a consequence of enhanced levels of ornithine decarboxylase activity in activated B cells. However, the levels of ornithine decarboxylase wane within 30 h post-stimulation, suggesting that B cells may acquire polyamines from an alternative source. Results in the present communication indicate that B cells initiate the transport of extracellular polyamines as they enter the G1 stage of the cell cycle. This induction of polyamine transport activity is seen after the stimulation of B cell cycle progression by both PMA and ionomycin, as well as cognate help from activated Th cells. The transport activities are energy and temperature sensitive, and can be competitively inhibited by unlabeled ligands. The results of the competition studies are compatible with the presence of at least two types of transporters, a low affinity transporter for both putrescine and spermidine, and a higher affinity transporter selective for spermidine. The results are discussed in terms of biochemical events associated with Th cell-mediated, B cell activation.

Transcription-independent activation of ornithine decarboxylase activity by heparin in cloned cerebral endothelial cells

Heparin, a highly sulfated glycosaminoglycan, is known to be obligatory for long-term endothelial cell cultures; it potentiates the mitogenic activities of endothelial cell growth factors and prolongs the replicative life span of the cells. Here we have shown that besides its growth factor-supportive role, heparin exerts a specific action on cerebral capillary endothelial cells (cECs), unrelated to serum or growth factors, by increasing activity of ornithine decarboxylase (ODC; EC 4.1.1.17) in these cells. For our experiments we have used two different types of cloned cECs: type I cECs, grown in the presence of endothelial cell growth factor and heparin, and type II cECs, usually cultivated without growth factors. Heparin action on ODC activity was shown to be dose dependent within the range of 1-100 micrograms/ml. Increasing concentrations of or depletion of endothelial cell growth factor from type I cultures had no effect on ODC activity. The increase in enzyme activity was highest after 30 min to 1 h of heparin treatment. As evidenced by northern analysis, the heparin-mediated enhancement of ODC activity was not accompanied by changes of ODC mRNA levels. Studies of DNA replication revealed that in the absence of heparin-binding growth factors, heparin did not affect the proliferative activity of cloned cECs.

Surface lysine and tyrosine residues are required for interaction of the major herpes simplex virus type 1 DNA-binding protein with single-stranded DNA

Modification of the herpes simplex virus type 1 major DNA-binding protein (ICP8) with reagents and conditions specific for arginine, lysine, and tyrosine residues indicates that surface lysine and tyrosine residues are required for the interaction of this protein with single-stranded DNA. Modification of either of these two amino acids resulted in a loss and/or modification of binding activity as judged by nitrocellulose filter assays and gel shift. Modification specific for arginine residues did not affect binding within the limits of the assays used. Finally, quenching of the intrinsic tryptophan fluorescence of ICP8 in the presence of single-stranded DNA either suggests involvement of this amino acid in the binding reaction or reflects a conformational change in the protein upon binding.

Polyamine transport and ornithine decarboxylase activity in hypoxic pulmonary artery smooth muscle cells

Hypoxia causes remodeling of the pulmonary circulation that is dependent on increases in lungs polyamine contents. Mechanisms by which polyamines are regulated in hypoxic lung cells are unknown, but ornithine decarboxylase (ODC) activity, the initial enzyme in de novo biosynthesis, is depressed and polyamine transport is augmented in lungs from hypoxic rats (R.-T. Shiao et al. 1990. Am. J. Physiol. 259:L351-L358). To determine if hypoxia directly influences polyamine regulatory mechanisms in pulmonary vascular cells, we examined [14C]spermidine (SPD) transport and ODC activity in bovine main pulmonary artery smooth muscle cells (PASMCs) cultured under standard (culture medium Po2: greater than 100 mm Hg), "normoxic" (culture medium Po2: 50 to 70 mm Hg), or "hypoxic" (culture medium Po2: 18 to 30 mm Hg) conditions. Uptake of [14C]SPD in cells cultured under standard conditions was temperature- and concentration-dependent, exhibited saturation kinetics, and was abolished by metabolic inhibition. Modeling of transport according to Michaelis-Menten kinetics revealed that [14C]SPD uptake in cells cultured under standard conditions was characterized by Km and Vmax values of 0.78 microM and 4.5 pmol/min/10(6) cells, respectively. In comparison to cells cultured under standard conditions, Km was unaffected by culture under normoxic or hypoxic conditions while Vmax was increased to 18 pmol/min/10(6) cells in normoxic cells and to 33 pmol/min/10(6) cells in preparations cultured under hypoxic conditions. Inhibition of ODC with alpha-difluoromethylornithine (DFMO) also induced SPD transport, as evidenced by an increase in the Vmax to 65 pmol/min/10(6) cells. Both hypoxia- and DFMO-induced increases in [14C]SPD transport were suppressed by cycloheximide and actinomycin D, thus highlighting the importance of protein and RNA synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Polyamines, vascular smooth muscle, and deoxycorticosterone acetate-salt hypertension

This study was performed to determine if an alteration in vascular polyamine contents is associated with the development of deoxycorticosterone acetate-salt hypertension. The effects of chronic administration of alpha-difluoromethylornithine, a specific irreversible inhibitor of ornithine decarboxylase and thus polyamine biosynthesis, on vascular polyamine contents, structure, and function as well as the development of hypertension was studied. Control and deoxycorticosterone acetate-salt rats received either tap water or a drinking solution containing alpha-difluoromethylornithine for 6 weeks, during which period systolic blood pressures were recorded. Vascular reactivity studies were performed on rings of aorta and tail artery. Medial thickness, vessel weight, and vascular polyamine contents were also assessed in these arteries. alpha-difluoromethylornithine treatment had no significant effect on either systolic blood pressure or vascular structure, function, and polyamine contents of control animals. The elevation in blood pressure and the increase in medial thickness, ring weight, and vascular polyamine contents as well as altered vascular reactivity observed in deoxycorticosterone acetate-salt rats was significantly attenuated by alpha-difluoromethylornithine treatment. These results are the first to demonstrate that vascular polyamine contents are elevated in the deoxycorticosterone acetate-salt rat and that chronic alpha-difluoromethylornithine treatment prevents the rise in vascular polyamines as well as the elevation in blood pressure and attendant changes in the vasculature. Thus, the increase in vascular polyamines may comprise a critical link between the initiating stimuli and the alterations in vascular structure and function implicated in the pathogenesis of deoxycorticosterone acetate-salt hypertension.

The major herpes simplex virus type-1 DNA-binding protein is a zinc metalloprotein

The primary amino acid sequence of the major herpes simplex virus type 1 (HSV-1)-infected cell polypeptide 8 (ICP8) deduced from the DNA sequence of the unique long open reading frame 29 (UL29 ORF) contains a potential metal-binding domain of the form Cys-X2-5-Cys-X2-15-A-X2-4-A where A may be either histidine or cysteine and X is any amino acid. The putative metal-binding sequence in ICP8 encompasses residues 499-512 as follows: C-N-L-C-T-F-D-T-R-H-A-C-V-H-. Atomic absorption analysis of several preparations of ICP8 indicates the presence of 1 mol of zinc/mol of protein. The zinc is resistant to removal by dialysis against concentrations of EDTA which deplete zinc from alcohol dehydrogenase. The bound zinc can be removed by reaction with the reversible sulfhydryl reagent p-hydroxymercurimethylsulfonate and the zinc-depleted protein transiently retains DNA binding activity. Digestion of both native and zinc-depleted ICP8 with V8 protease indicates that the bound zinc is required for the structural integrity of the protein.

Lifetime toxicity/carcinogenicity studies of FD & C red no. 40 (allura red) in mice

FD & C Red No. 40 (allura red) was fed to Charles River HaM/ICR (CD-1) (study A) and CD-1 outbred (study B) mice as a dietary admixture in two separate lifetime toxicity/carcinogenicity studies. Each study included an in utero exposure phase during which the colouring was fed at dietary concentrations of 0.0, 0.37, 1.39 or 5.19% throughout the mating, gestation and lactation periods. After random selection, the lifetime exposure phase was initiated using the same dietary concentrations with 50 mice/sex/group in study A and 100 mice/sex/group in study B. Exposure was for 104 wk in study A and 109 wk in study B. No compound-related adverse effects were observed. The no-observable-adverse-effect level in these studies was 5.19%; approximately 7300 and 8300 mg/kg body weight/day for male and female mice, respectively.

The development of competence in resting B cells. The induction of cyclic AMP and ornithine decarboxylase activity after direct contact between B and T helper cells

In the present communication, an experimental approach is utilized that facilitates the study of biochemical processes induced in B cells after their interaction with Th cells. In this approach, Th cell clones are stimulated for 18 h upon anti-CD3-coated plates, fixed with paraformaldehyde, and added at a 2 to 3:1 ratio to small, resting B cells (isolated from Percoll gradients). Th cells not stimulated on anti-CD3-coated plates, but fixed with paraformaldehyde, serve as controls for these experiments. The activated, fixed Th cells induce a transient, sixfold increase in B cell levels of cAMP, as well as an increase in B cell expression of ornithine decarboxylase (ODC) activity. This enzyme initiates the synthesis of polyamines and has been shown to be increased as cells enter the growth phase. In addition, previous studies have shown that the cellular levels of ODC activity are controlled by a multi-tiered regulatory cascade. To examine this aspect, polyclonally stimulated B cells were studied. Such cells demonstrated a gradual increase in ODC mRNA levels that peaked between 6 and 15 h and can be partially explained by a three- to fourfold increase in mRNA stability but not by changes in the enzyme affinity for substrate. The increase in ODC mRNA occurs in the absence of protein synthesis, suggesting that the ODC gene is a member of the immediate/early gene family. Finally, the early increase in ODC mRNA was enhanced in cells in which cAMP levels were artificially elevated, suggesting the possibility that the cAMP-dependent signaling pathway participates during the regulation of this gene expression. The significance of these experimental results concerning the process of B cell activation is discussed.

The development of competence in resting B cells. The induction of cyclic AMP and ornithine decarboxylase activity after direct contact between B and T helper cells

In the present communication, an experimental approach is utilized that facilitates the study of biochemical processes induced in B cells after their interaction with Th cells. In this approach, Th cell clones are stimulated for 18 h upon anti-CD3-coated plates, fixed with paraformaldehyde, and added at a 2 to 3:1 ratio to small, resting B cells (isolated from Percoll gradients). Th cells not stimulated on anti-CD3-coated plates, but fixed with paraformaldehyde, serve as controls for these experiments. The activated, fixed Th cells induce a transient, sixfold increase in B cell levels of cAMP, as well as an increase in B cell expression of ornithine decarboxylase (ODC) activity. This enzyme initiates the synthesis of polyamines and has been shown to be increased as cells enter the growth phase. In addition, previous studies have shown that the cellular levels of ODC activity are controlled by a multi-tiered regulatory cascade. To examine this aspect, polyclonally stimulated B cells were studied. Such cells demonstrated a gradual increase in ODC mRNA levels that peaked between 6 and 15 h and can be partially explained by a three- to fourfold increase in mRNA stability but not by changes in the enzyme affinity for substrate. The increase in ODC mRNA occurs in the absence of protein synthesis, suggesting that the ODC gene is a member of the immediate/early gene family. Finally, the early increase in ODC mRNA was enhanced in cells in which cAMP levels were artificially elevated, suggesting the possibility that the cAMP-dependent signaling pathway participates during the regulation of this gene expression. The significance of these experimental results concerning the process of B cell activation is discussed.

Ventilatory dysfunction precedes pulmonary vascular changes in monocrotaline-treated rats

Rats with established monocrotaline (MCT)-induced pulmonary hypertension also exhibit a profound increase in lung resistance (RL) and a decrease in lung compliance. Because airway/lung dysfunction could precede and influence the evolution of MCT-induced pulmonary vascular disease, it is important to establish the temporal relationship between development of pulmonary hypertension and altered ventilatory function in MCT-treated rats. To resolve this issue, we segregated 47 young Sprague-Dawley rats into four groups: control (n = 13), MCT1 (n = 9), MCT2 (n = 11), and MCT3 (n = 14). Each MCT rat received a single subcutaneous injection of MCT (60 mg/kg) 1 MCT1), 2 (MCT2), or 3 (MCT3) wk before the functional study. At 1 wk after MCT, significant increases in RL and alveolar wall thickness were observed, as was a significant decrease in carbon monoxide diffusing capacity (DLCO). Medial thickness of pulmonary arteries (50-100 microns OD) and right ventricular hypertrophy were not observed until 2 and 3 wk post-MCT, respectively. Coincident with the right ventricular hypertrophy at 3 wk post-MCT were decreased DLCO and increased alveolar wall thickness and lung dry weight. Pressure-volume curves of air-filled and saline-filled lungs showed marked rightward shifts during the 1st and 2nd wk after MCT administration and then decreased at the 3rd wk. These data suggest that MCT-induced alterations in airway/lung function preceded those of pulmonary vasculature and, therefore, implicate airway/lung dysfunctions as potentially contributing to the later development of pulmonary vascular abnormalities.

Mechanisms of lung polyamine accumulation in chronic hypoxic pulmonary hypertension

Chronic hypoxia causes polyamine-dependent hypertensive pulmonary vascular remodeling (J. E. Atkinson. J. W. Olson, R. J. Altierre, and M. N. Gillespie, J. Appl. Physiol. 62: 1562-1568, 1987), but mechanisms by which lung polyamine contents are elevated have not been established. This study measured polyamine contents, biosynthetic activities, and transport in lungs of rats exposed to hypobaric hypoxia (simulated altitude: 4,570 m) for 4-14 days. Hypoxia increased lung contents of spermidine and spermine within 40 h and of putrescine within 4 days. These changes preceded hypoxia-induced increases in pulmonary arterial pressure and development of right ventricular hypertrophy. Additional experiments determined whether increased lung polyamine contents could be ascribed to elevated activity of ornithine decarboxylase (ODC), the rate-limiting enzyme in conversion of ornithine to putrescine. Lung ODC activity did not differ from controls at 40 h posthypoxia and was reduced below control levels from 4-14 days of exposure. Putrescine transport kinetics were assessed in isolated, salt solution-perfused lungs. Apparent Km for putrescine uptake was increased from 10.4 microM in control lungs to 16.9 microM in lungs from rats maintained for 7 days in an hypoxic environment. Maximal velocity (Vmax) of lung putrescine transport was increased from 1.67 nmol.g-1.min-1 in controls to 2.65 in hypoxic lungs. Putrescine efflux also was altered by hypoxic exposure; T1/2 for loss of diamine from a slowly effluxing pool was increased from 60.6 min in controls to 91.5 min in hypoxic lungs.(ABSTRACT TRUNCATED AT 250 WORDS)

A Veterans Administration Cooperative Study of biphasic calcium phosphate ceramic in periodontal osseous defects

One hundred thirty-seven V.A. patients were randomized to one of three treatment groups to evaluate the efficacy of biphasic calcium phosphate (BCP) ceramic in the treatment of periodontal osseous defects. This material was tested against both autogenous bone implant and open flap curettage procedures. Baseline probing attachment level, Navy plaque index, and gingival index were recorded for all patients. These parameters were monitored for 3 years. At the end of this period, 101 patients had completed the study. Although the plaque and gingival indices steadily increased with time, there were no statistically significant differences among the treatment groups. Patients in the ceramic group had a gain in attachment level of 1.0 mm; those in the curettage group, 0.9 mm; and 0.4 mm for those in the bone implant group. Although the BCP patients had a greater gain, the difference was not statistically significant. In this veteran population, not only did BCP patients fail to outperform those in the control groups, all three treatment groups were similarly ineffective.