Biomedical subjects

J W Olson

Publications and source records attributed to J W Olson.

At least 37 records · Page 2Linked to original sources

PubMed1997

The influence of maxillary sinus augmentation on the success of dental implants through second-stage surgery.

An interim evaluation of the status of 102 implants placed in 42 augmented sinuses in 27 patients involved in an alternate category of the Dental Implant Clinical Research Group's long-term, randomized, prospective clinical investigation is presented. Autogeneic, allogeneic, and alloplastic sinus grafts were used, individually or mixed. Through second-stage surgery, 101 implants were found to be integrated. The mean Periotest value at uncovering was -3.36, with a standard deviation of 4.19. The results suggest that root form implants placed in augmented sinuses are successful through second-stage surgery, regardless of the augmentation material or implant design used.

Adult↗

PubMed1997

Multiple polyamine regulatory pathways control compensatory cardiovascular hypertrophy in coarctation hypertension.

While a number of factors may initiate structural alterations within the cardiovascular system in response to hypertension, there are obligate cellular signaling mechanisms, such as the polyamines, through which they must operate. This study examined the effects of polyamine synthesis inhibition using eflornithine, a suicide inhibitor of ornithine decarboxylase on blood pressure, compensatory remodeling of the cardiovascular system, and cardiac and aortic polyamine contents using an aortic coarctation model in rats. Eflornithine treatment failed to reduce carotid arterial blood pressure and actually significantly elevated vascular pressure above and below the coarctation site by 14 days of hypertension. Eflornithine only transiently reduced aortic polyamine content of hypertensive rats while this agent reduced coarctation-induced aortic medial wall thickening and the synthesis/deposition of fibronectin and laminin in the hypertensive aorta. Increases in left ventricular mass and polyamine content were concomitantly reduced in hypertensive rats administered eflornithine. These results suggest that multiple polyamine regulatory pathways may maintain vascular polyamine content in response to aortic coarctation; however de novo polyamine synthesis is essential for select aspects of vascular remodeling, including matrix synthesis. Cardiac tissue, in contrast, may rely principally on de novo polyamine synthesis.

Animals↗

PubMed1996

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.

Antineoplastic Agents↗

PubMed1996

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.

Amino Acid Sequence↗

PubMed1996

Temporal alterations in basement membrane components in the pulmonary vasculature of the chronically hypoxic rat: impact of hypoxia and recovery.

The hypoxic model of pulmonary hypertension was used to examine temporal alterations in the deposition of the basement membrane (BM) and components of fibronectin, laminin, and Type IV collagen within vascular, airway, and gas exchange compartments of the lung. Because hypoxic pulmonary hypertension is a reversible model of hypertension, changes in fibronectin and laminin synthesis/deposition in the recovering lung were also examined. Long-term hypoxic exposure produced decreases in body weight, increased right ventricular and lung dry weights and elevations in pulmonary arterial pressure. Immunohistochemical analysis revealed consistent and progressive increases in the deposition of fibronectin and laminin, but not type IV collagen, in the subendothelial and medial BMs of large and small pulmonary arteries, but not in airways or lung parenchyma. These changes were observed by day 4 of hypoxia and were most prominent in the conducting vasculature. Northern analysis showed a biphasic pattern of alterations in steady-state levels of BM component mRNA in hypoxic rats with early reductions at days 4 and 7 followed by increases at day 12. Recovery from 12 days of hypoxia resulted in regression of pulmonary hypertension and right ventricular hypertrophy but not increased lung weight. Immunohistochemical analysis of fibronectin, laminin, and type IV collagen levels in the vasculature showed a temporal regression to levels that were not remarkably different from time-matched controls at day 30 of recovery. Northern analysis of lungs from hypoxic-recovery rats revealed increased steady-state levels of mRNA for fibronectin, laminin, and type IV collagen at all time points. These data indicate that long-term hypoxic exposure elicits marked alterations in the synthetic capacity and deposition of the important cell attachment BM glycoproteins fibronectin and laminin. In addition, recovery from hypoxia appears to be characterized by a lack of increased fibronectin and laminin levels in the conducting vasculature, suggesting a marked and rapid reorganization of the vascular BMs on both hypoxic exposure and recovery from hypoxia.

Animals↗

PubMed1996

Regulation of ornithine decarboxylase by hypoxia in pulmonary artery smooth muscle cells.

The polyamines are a family of low-molecular-weight organic cations that play essential intracellular regulatory roles in cell growth and differentiation. Elevations in cellular polyamine contents necessary for most physiological and pathological events in the lung appear to be driven by increase de novo synthesis. In contrast, increases in lung cell polyamines required for hypoxic pulmonary vascular disease can be attributed to augmented transmembrane polyamine transport which may, in turn, be the result of hypoxia-related decreases in the activity of the initial and generally rate-limiting enzyme in de novo polyamine synthesis, ornithine decarboxylase (ODC). To begin to define the unusual mechanism whereby hypoxia governs polyamine regulatory pathways, the present study examined the impact of varying severity and durations of hypoxic exposure on ODC activity and mRNA content in cultured bovine main pulmonary artery smooth muscle cells (PASMC). The effect of hypoxia on the activity of another rate-limiting enzyme in polyamine synthesis, S-adenosylmethionine decarboxylase (AdoMet-DC), also was examined. Hypoxia caused time-dependent decreases in ODC and AdoMet-DC activities that were related to the severity of hypoxic exposure. Similarly, ODC mRNA content also was depressed by hypoxic exposure. The relationship between the decline in ODC activity and mRNA content was roughly linear. To determine whether hypoxia impairs ODC mRNA stability, two different inhibitors of transcription and Northern analyses were used to follow the decay in ODC mRNA abundance in hypoxic and normoxic PASMC. Densitometric scanning of Northern analysis indicated that ODC mRNA stability did not differ between hypoxic and normoxic PASMC. These results suggest that the reduction in ODC activity provoked by hypoxia in cultured bovine PASMC can be ascribed in part to a diminished transcriptional rate rather than to alterations in mRNA stability.

Adenosylmethionine Decarboxylase↗

PubMed1996

The potential of a novel polyamine transport inhibitor in cancer chemotherapy.

The polyamines, putrescine (PUT), spermidine (SPD) and spermine (SPM), are a family of low molecular weight organic cations that are essential for cell growth, differentiation and neoplastic transformation. The marked compensatory increase in extracellular polyamine influx may be a reason for the unsatisfactory clinical chemotherapeutic effect of polyamine synthesis blockers like difluoromethylornithine (DFMO). In this study, a polymeric conjugate of SPM (poly-SPM) that blocks the import of polyamines into mammalian cells was used to test the potential therapeutic exploitation of the polyamine transport system in anticancer therapy. Our results indicate that a temperature-dependent polyamine transport system is expressed in two human cancer cell lines, MES-SA uterine sarcoma cells, K562 leukemic cells and their respective multiple drug resistance (MDR) positive counterparts, Dx5 and K562/R7 cells. The V(max) values for 14C-PUT and 14C-SPD uptake were significantly higher in MES-SA than in Dx5 cells, whereas the respective Km values were significantly lower. Addition of 20 microM poly-SPM reduced both the uptake of 14C-polyamines and the cellular polyamine contents in both cancer cell lines. In addition, the poly-SPM conjugate evoked a concentration-dependent cytotoxicity in MES-SA and K562 cells and their MDR-positive variants. Presence of aminoguanidine, an amine oxidase blocker, failed to alter the IC50 values generated with poly-SPM, which indicates that this polymer is not a substrate for amine oxidase. Moreover, coadministration of 25 microM SPD reversed the cytotoxic effect exerted by poly-SPM on both the MES-SA and Dx5 cells as reflected by an increase in their IC50 values. Relative to parental cells, the MDR-positive variants exhibited a lower 14C-polyamine uptake rate and were more resistant to the cytotoxic effect of poly-SPM. Pretreatment with 1 mM DFMO for 24 hr significantly increased polyamine transport, but failed to reduce intracellular SPM contents or exert a cytotoxic effect in both cancer cell lines. On other hand, the combination of DFMO and poly-SPM produced a greater depletion of polyamine content accompanied by a higher cytotoxicity than either agent alone. These results provide the first direct evidence that pharmacologic interruption of polyamine uptake may be an effective approach to cancer therapy. In addition, it appears that expression of MDR influences polyamine transport and renders cells more resistant to the cytotoxic effects of SPM polymer.

Antineoplastic Agents↗

PubMed1995

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.

Amino Acid Sequence↗

PubMed1995

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.

Animals↗

PubMed1995

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.

Animals↗

PubMed1994

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.

Adenosine Triphosphate↗

PubMed1994

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.

Animals↗

PubMed1994

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.

Acetyltransferases↗

PubMed1994

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)

Animals↗

PubMed1994

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)

Animals↗

PubMed1993

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.

Animals↗

PubMed1993

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.

Animals↗

PubMed1993

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.

Animals↗