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R J Phipps

Publications and source records attributed to R J Phipps.

At least 19 recordsLinked to original sources
PubMed2006

Long-term risedronate treatment normalizes mineralization and continues to preserve trabecular architecture: sequential triple biopsy studies with micro-computed tomography.

The objective of the study was to assess the time course of changes in bone mineralization and architecture using sequential triple biopsies from women with postmenopausal osteoporosis (PMO) who received long-term treatment with risedronate. Transiliac biopsies were obtained from the same subjects (n = 7) at baseline and after 3 and 5 years of treatment with 5 mg daily risedronate. Mineralization was measured using 3-dimensional (3D) micro-computed tomography (CT) with synchrotron radiation and was compared to levels in healthy premenopausal women (n = 12). Compared to the untreated PMO women at baseline, the premenopausal women had higher average mineralization (Avg-MIN) and peak mineralization (Peak-MIN) by 5.8% (P = 0.003) and 8.0% (P = 0.003), respectively, and lower ratio of low to high-mineralized bone volume (BMR-V) and surface area (BMR-S) by 73.3% (P = 0.005) and 61.7% (P = 0.003), respectively. Relative to baseline, 3 years of risedronate treatment significantly increased Avg-MIN (4.9 +/- 1.1%, P = 0.016) and Peak-MIN (6.2 +/- 1.5%, P = 0.016), and significantly decreased BMR-V (-68.4 +/- 7.3%, P = 0.016) and BMR-S (-50.2 +/- 5.7%, P = 0.016) in the PMO women. The changes were maintained at the same level when treatment was continued up to 5 years. These results are consistent with the significant reduction of turnover observed after 3 years of treatment and which was similarly maintained through 5 years of treatment. Risedronate restored the degree of mineralization and the ratios of low- to high-mineralized bone to premenopausal levels after 3 years of treatment, suggesting that treatment reduced bone turnover in PMO women to healthy premenopausal levels. Conventional micro-CT analysis further demonstrated that bone volume (BV/TV) and trabecular architecture did not change from baseline up to 5 years of treatment, suggesting that risedronate provided long-term preservation of trabecular architecture in the PMO women. Overall, risedronate provided sustained benefits on mineralization and architecture, two key determinants of bone strength, over 5 years lending support for its long-term efficacy in fracture risk reduction.

Adult↗
PubMed2005

Novel insights into actions of bisphosphonates on bone: differences in interactions with hydroxyapatite.

Bisphosphonates are now the most widely used drugs for diseases associated with increased bone resorption, such as osteoporosis. Although bisphosphonates act directly on osteoclasts, and interfere with specific biochemical processes such as protein prenylation, their ability to adsorb to bone mineral also contributes to their potency and duration of action. The aim of the present study was to compare the binding affinities for hydroxyapatite (HAP) of 6 bisphosphonates currently used clinically and to determine the effects of these bisphosphonates on other mineral surface properties including zeta potential and interfacial tension. Affinity constants (K(L)) for the adsorption of bisphosphonates were calculated from kinetic studies on HAP crystal growth using a constant composition method at 37 degrees C and at physiological ionic strength (0.15 M). Under conditions likely to simulate bisphosphonate binding onto bone, there were significant differences in K(L) among the bisphosphonates for HAP growth (pH 7.4) with a rank order of zoledronate > alendronate > ibandronate > risedronate > etidronate > clodronate. The measurements of zeta potential show that the crystal surface is modified by the adsorption of bisphosphonates in a manner best explained by molecular charges related to the protonation of their side-chain moieties, with risedronate showing substantial differences from alendronate, ibandronate, and zoledronate. The studies of the solid/liquid interfacial properties show additional differences among the bisphosphonates that may influence their mechanisms for binding and inhibiting crystal growth and dissolution. The observed differences in kinetic binding affinities, HAP zeta potentials, and interfacial tension are likely to contribute to the biological properties of the various bisphosphonates. In particular, these binding properties may contribute to differences in uptake and persistence in bone and the reversibility of effects. These properties, therefore, have potential clinical implications that may be important in understanding differences among potent bisphosphonates, such as the apparently more prolonged duration of action of alendronate and zoledronate compared with the more readily reversible effects of etidronate and risedronate.

Bone Density Conservation Agents↗
PubMed2002

Effects of risedronate, alendronate, and etidronate on the viability and activity of rat bone marrow stromal cells in vitro.

The effects of risedronate, alendronate, and etidronate were assessed in calcifying fibroblastic colony-forming unit (CFU-f) cultures of rat bone marrow cells in vitro. Biphasic effects on the formation of bone-like colonies were observed. Treatment with high concentrations (10(-5)-10(-4)M) of alendronate and risedronate caused a total inhibition of colony formation whereas etidronate had relatively little effect. It was also found that intermediate concentrations (10(-6)M) of alendronate and risedronate decreased the formation of colonies displaying osteoblastic characteristics such as alkaline phosphatase expression, collagen accumulation, and calcification. At lower concentrations (10(-9)-10(-7)M), risedronate and alendronate increased the formation of fibroblastic colonies, suggesting a mild anabolic effect, however, the formation of colonies with osteoblastic properties was not affected. Treating the cells with a combination of bisphosphonate and 1 mM geranylgeraniol could to some extent abrogate the cytotoxic effects of alendronate or risedronate, suggesting the involvement of the mevalonate pathway. The colony-stimulating activity of these bisphosphonates was, however, unaffected.

Alendronate↗
PubMed2001

Nitrogen-containing bisphosphonates induce apoptosis of Caco-2 cells in vitro by inhibiting the mevalonate pathway: a model of bisphosphonate-induced gastrointestinal toxicity.

Bisphosphonates have become an important addition to the pharmacological armamentarium against postmenopausal osteoporosis. One of the major side effects of oral therapy with some nitrogen-containing bisphosphonates appears to be gastrointestinal (GI) intolerability, particularly esophageal irritation and ulceration. Because nitrogen-containing bisphosphonates can cause apoptosis in a variety of cell types in vitro, by inhibiting the mevalonate pathway, we hypothesized that the effect of these agents on the GI tract may be due to apoptosis or inhibition of growth of gut epithelial cells. A comparison between clodronate, etidronate, pamidronate, alendronate, and risedronate demonstrated that only the nitrogen-containing bisphosphonates were effective at inducing apoptosis or inhibiting proliferation of Caco-2 human epithelial cells in vitro, at concentrations of between 10 and 1000 micromol/L. The ability of nitrogen-containing bisphosphonates to cause apoptosis and inhibit Caco-2 cell proliferation was due to inhibition of the mevalonate pathway, because the addition of farnesol, oxidized low-density lipoprotein (LDL) cholesterol, or especially geranylgeraniol suppressed the effects. Furthermore, pamidronate, alendronate, and risedronate inhibited protein prenylation in Caco-2 cells, as determined by analysis of the processing of Rap1A, a prenylated small GTPase. These studies suggest that the effects of nitrogen-containing bisphosphonates observed in the GI tract may be due to inhibition of proliferation or apoptosis of gut epithelial cells, following loss of prenylated proteins and sterols.

Apoptosis↗
PubMed2000

Treatment with risedronate or alendronate prevents hind-limb immobilization-induced loss of bone density and strength in adult female rats.

Immobilization leads to rapid loss of bone mass and mechanical competence, and long-term immobilization or repeated periods of short-term immobilization can have serious skeletal consequences and may lead to increased fracture liability. The aim of the present preclinical study was, therefore, to assess whether two antiresorptive agents, risedronate (Ris) or alendronate (Aln), would be capable of preventing immobilization-induced loss of bone mass and strength in rats. The study was designed as a dose-response study, and the site-specific effects of immobilization and of treatment are described. Four-month-old virgin female Sprague-Dawley rats were divided into eight groups with 12 animals in each group: (1) immobilized (Imm) control; (2) normal control; (3) Imm + Ris 0.1 mg/kg body weight/day (b.w./day); (4) Imm + Ris 0.2 mg/kg b.w./day; (5) Imm + Ris 1.0 mg/kg b.w./day; (6) Imm + Aln 0.2 mg/kg b.w./day; (7) Imm + Aln 1.0 mg/kg b.w./day; and (8) Imm + Aln 2.0 mg/kg b.w. /day. In groups 1 and 3-8, the right hind leg was immobilized with an elastic bandage. The study period was 28 days. The effects of unilateral hind-limb immobilization and of treatment were determined by dual-energy X-ray absorptiometry (DEXA) measurements on tibiae and by biomechanical testing of femora at three different sites: diaphysis; femoral neck; and distal metaphysis. Bilateral measurements were performed (on the immobilized and nonimmobilized legs). Immobilization induced a significant loss of bone mineral density (BMD) at the proximal tibial metaphysis, but no change at the mid-diaphysis. Furthermore, immobilization induced a loss of bone strength at the two femoral metaphyses, but no change was seen in three-point bending of the diaphysis. Both risedronate and alendronate treatment showed a dose-dependent protection against the immobilization-induced loss of bone density and strength at the metaphyses. We conclude that, in rats, short-term hind-limb immobilization affects only the metaphyses and that no changes are seen in the diaphysis. Both risedronate and alendronate can prevent immobilization-induced bone loss at the metaphyses. The present study confirms the importance of examining several skeletal sites when testing the efficacy of therapeutic agents.

Alendronate↗
PubMed2000

Gastric damage in the rat with nitrogen-containing bisphosphonates depends on pH.

BACKGROUND: The use of nitrogen-containing bisphosphonates (N-BPs) has been reported to be associated with gastrointestinal intolerance. The fasted, indomethacin-treated rat provides a model for assessing the gastrointestinal effects of these compounds. AIMS: The aims of this study were to elucidate the effect of pH on N-BP-induced gastric damage, and to evaluate the structure-activity relationship between N-BP anti-resorptive and gastric effects. METHODS: Fasted rats were dosed concomitantly with indomethacin (40 mg/kg, subcutaneously) and an N-BP (pamidronate, alendronate, or risedronate at 150 or 300 mg/kg, orally), with the N-BP dosing solutions adjusted to pH 2, 4 or 7. The aminopentane and aminohexane N-BPs (150, 225 or 300 mg/kg, orally) were only tested at pH 4 only. RESULTS: Nitrogen-containing bisphosphonate-induced gastric damage was pH-dependent, with increased damage at increasing pH. CONCLUSIONS: Gastric damage potential did not correlate with bone anti-resorptive effects, and the more potent anti-resorptive N-BPs were not necessarily more damaging to the stomach.

Administration, Oral↗
PubMed1997

Nonclinical model for assessing gastric effects of bisphosphonates.

Gastrointestinal intolerance has been associated with amino bisphosphonate therapy in the clinic. The objective of this study was to develop a model for assessing bisphosphonate-induced gastric damage that may aid in the development of future bisphosphonate therapies. Rats were dosed concomitantly with indomethacin (40 mg/kg, subcutaneously) and an amino or pyridinyl bisphosphonate (orally at. 150, 225 or 300 mg/kg). The bisphosphonates studied were pamidronate and alendronate (primary amino bisphosphonates) and risedronate and NE-97221 (pyridinyl bisphosphonates). Macroscopically, alendronate induced significantly (P < 0.05) more antral damage (both lesion length and number) than pamidronate and risedronate at 225 and 300 mg/kg, and more than NE-97221 at 300 mg/kg. NE-97221 induced significantly more antral damage (lesion length) than risedronate at 225 mg/kg and a greater number of lesions compared to pamidronate and risedronate at 225 and 300 mg/kg. The model was validated histologically, and macroscopic findings correlated with histologic evidence of antral mucosal necrosis and inflammatory infiltration of the lamina propria. The calcium chelators EGTA and EDTA did not induce gastric damage in this model when dosed according to the same protocol as the nitrogen-containing bisphosphonates. This suggests that calcium chelation does not account for the gastric effects in this model. The fasted, indomethacin-treated rat provides a novel nonclinical model to assess gastric effects of bisphosphonates, which may aid in the development of future bisphosphonate therapies. These data suggest that when expressed on an actual or anticipated clinical dose basis for osteoporosis (pamidronate, 150 mg; alendronate, 5-10 mg; risedronate and NE-97221, 5 mg), primary amino bisphosphonates may have a greater potential for inducing gastric damage than do pyridinyl bisphosphonates.

Alendronate↗
PubMed1990

Identification and characterization of B2 bradykinin receptors in sheep nasal turbinate membranes.

Because bradykinin (BK) has been implicated as a mediator of upper respiratory tract symptomatology, specific 3H-BK binding was investigated in membrane homogenates prepared from sheep nasal turbinate tissue in order to identify and characterize the BK receptor subtype(s) present. 3H-BK saturation and Scatchard analyses revealed a single, high affinity, saturable site (KD of 0.098 nM) with a density of 0.44 pmol/g wet weight tissue. Competition experiments using B1 and B2 receptor agents revealed a B2-BK receptor pharmacology; the B2 agents BK, Lys-BK, NPC-567, [D-Phe7]-BK and [Thi,5,8 D-Phe7]-BK displayed nM affinity while the B1 agents [des-Arg9]-BK and [Leu,8 des-Arg9]-BK competed in the uM range. The absolute and rank order of affinities in this tissue paralleled that found in the guinea pig ileum. No specific binding was found using the putative B1 receptor radioligand 3H-[des-Arg9]-BK. Specific B2-BK receptor binding was not effected by the addition of non-hydrolyzable guanine or adenine nucleotides. These data confirm the presence of B2-BK receptors in this tissue and provide support for a role of BK in nasal function.

Animals↗
PubMed1990

Nasal absorption of interferon: enhancement by surfactant agents.

The effect of spraying the nasal mucosa with an aerosol of recombinant human interferon-alpha (IFN-alpha 2a) was studied in an animal model, the sheep, because cultures of sheep cells were found to be responsive to the antiviral activity of this IFN. Binding assays with 125I-labeled IFN-alpha 2a detected very few receptors in sheep nasal mucosa, but a membrane fraction prepared from this mucosa had abundant high-affinity receptors. Nasal mucosa homogenates were prepared from the turbinates of sheep that had been sprayed with IFN-alpha 2a aerosols, and the 2',5'-oligoadenylate (2-5A) activity induced in response was measured. To try to enhance the permeability of the mucosa, surfactant agents were added to the IFN and aerosols generated. There were measurable levels of 2-5A synthetase after aerosols with added sodium deoxycholate or, better, polyoxyethylene 9-lauryl ether. This latter surfactant was well tolerated in previous studies with intranasally administered insulin. The level of 2-5A synthetase induced was related to the dose of IFN, and the increased activity persisted up to 72 h after an IFN aerosol. These studies suggest that surfactant agents may make IFN aerosols much more effective for the prophylaxis of respiratory virus infections.

2',5'-Oligoadenylate Synthetase↗
PubMed1990

Effect of ozone on the postnatal development of lamb mucociliary apparatus.

We determined whether exposure to O3 early in the postnatal period impairs the normal development of the mucociliary apparatus in lambs and whether such changes lead to prolonged abnormalities in mucociliary function. Lambs were exposed to air (controls) or to 1 ppm O3 for 4 h/day for 5 days during the 1st wk of life. Tracheal mucus velocity (TMV), a marker of lung mucociliary clearance, was measured in vivo at birth (0 wk) and up to 24 wk later, and tracheal secretory function was measured (in vitro) and the morphology of the tracheal mucosa was determined at 0 and 2 wk in both groups. In the control group, TMV increased 94% from 0 to 2 wk (P less than 0.05), continued to increase until reaching a plateau at 8 wk, and then remained constant from 8 to 24 wk. In contrast, O3-exposed lambs showed a 24% decrease in TMV from 0 to 2 wk (P less than 0.05 vs. control), and throughout the remaining time TMV remained below (P less than 0.05) that observed in control lambs. O3 exposure partially prevented the age-dependent decrease in basal secretion of tracheal macromolecules normally observed between 0 and 2 wk. These changes in secretory function were associated with a significant increase in tissue conductance (37%, P less than 0.05 vs. 0 wk), predominantly the result of active chloride secretion. The functional changes induced by O3 were associated with a retardation of the normal morphological development of the tracheal epithelium.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Developmental changes in the tracheal mucociliary system in neonatal sheep.

We studied the postnatal development of the tracheal epithelium and mucociliary system in neonatal sheep. Secretion of macromolecules (radiolabeled with 35SO4 and [3H]-threonine), unidirectional fluxes of Cl-, Na+, and water (measured with radioactive tracers), and ciliary beat frequency (CBF) were measured in tracheal tissues in vitro. Tracheal mucus transport velocity (TMV) was measured in vivo. Sheep were studied at 0, 2, 4, 8, and greater than 24 (adult) wk after birth. In newborn sheep trachea, secretion of macromolecules was significantly elevated (cf. adults), and there was basal net secretion of Cl- under short-circuit and open-circuit conditions. This induced open-circuit secretion of Na+. Secretion of macromolecules decreased rapidly by 2 wk (by 40-50%) and was not different from adult values by 4 wk. Active Na+ absorption developed rapidly, and from 2 wk onward it predominated under open-circuit conditions, inducing net Cl- absorption. These changes in secretory function were associated with an age-related increase in TMV, whereas inherent tracheal CBF was unchanged. In sheep, therefore, the newborn's trachea has elevated secretion of macromolecules and secretes Cl- and liquid under basal conditions. Normal secretory function (a reduction in secretion of macromolecules coupled with net absorption of ions and presumably of liquid also) approaches adult function by 2-4 wk of age.

Animals↗
PubMed1987

Bacterial pneumonia stimulates macromolecule secretion and ion and water fluxes in sheep trachea.

In vivo instillation of Pasteurella haemolytica (greater than or equal to 10(7) colony-forming units/kg) into a lobar bronchus of sheep produced bacterial pneumonia by 7 days postinoculation. Infection was verified bacteriologically and histologically. Macromolecule secretion and ion and water fluxes were subsequently measured in tracheal tissues in vitro and were compared with values from sham-infected sheep. Macromolecules were radiolabeled with 35SO4 and [3H]threonine, and we measured the secretion of macromolecule-bound radiolabel onto the mucosa. Unidirectional fluxes of Cl-, Na+, and water were measured with radioactive tracers under open-circuit and short-circuit conditions. Lung infection increased basal secretion of bound 35SO4 (by 189%) and bound [3H]-threonine (by 110%). It significantly increased net Na+ absorption under open- and short-circuit conditions and induced open-circuit net absorption of Cl- and water (16 +/- 29 microliters X cm-2 X h-1). These changes were associated with specific recruitment of neutrophils and elevated levels of arachidonate metabolites (thromboxane B2 and leukotriene B4) in the airways. Thus the bacterial pneumonia-induced changes in tracheal mucus secretion may be the result of airway inflammation.

Animals↗
PubMed1986

Mucus-glycoproteins (mucins) of the cat trachea: characterisation and control of secretion.

Glycoproteins produced by the tracheae of anaesthetized cats were radiolabelled biosynthetically by a pulse administration of Na2 35SO4 and [3H]glucose into the tracheal lumen. Subsequently, radiolabelled secretions were washed from the tracheal lumen. Repeated doses of pilocarpine and then ammonia vapour were given to stimulate secretion. Pilocarpine-stimulated glycoproteins, which came mainly from the submucosal glands, were particularly enriched with 35S. Ammonia-stimulated secretions, which probably came mostly from the microvillous border of the surface epithelium, contained mainly 3H radioactivity but little 35S. Two negatively-charged glycoproteins of different molecular size were identified in the secretions: the larger component was excluded on Sepharose CL-4B and it had a higher 3H 35S ratio than the smaller component which was retarded on Sepharose CL-4B. The relative amount of the smaller component decreased progressively with repeated pilocarpine stimulation and it was not detected in secretions induced by ammonia. Pilocarpine stimulation caused little alteration in carbohydrate composition of the secreted glycoproteins. In response to ammonia, glycoproteins were secreted with a high sialic acid content but quantitatively they represented a small amount of material compared with that induced by pilocarpine. These findings suggest that tracheal glycoproteins from different epithelial-cell sources have distinctive chemical compositions and that their secretions may be independently regulated. The 35S-rich high-molecular-weight glycoproteins from the submucosal glands were of the mucin-type but those derived from the microvillus border may represent a different class of airway glycoproteins from typical epithelial mucins.

Alcian Blue↗
PubMed1986

Effects of 0.5 ppm ozone on glycoprotein secretion, ion and water fluxes in sheep trachea.

We studied the effects of ozone (O3) exposure on airway mucus secretion. Sheep were exposed in vivo to 0.5 ppm O3, 4 h/day for 2 days (acute, n = 6), 6 wks (chronic, n = 6) or 6 wks + 1 wk recovery (chronic + recovery, n = 6). Secretion of glycoproteins (radiolabeled with 35SO4 and [3H]threonine), and transepithelial fluxes of Cl-, Na+ and water were subsequently measured in tracheal tissues in vitro, and were compared with values from control, unexposed sheep (n = 8). Acute O3 exposure increased basal secretion of sulfated glycoproteins (P less than 0.05), but had no effect on ion fluxes. Chronic exposure reduced basal glycoprotein secretion, but increased net Cl- secretion. Under open-circuit conditions, chronic exposure also induced net water secretion (P less than 0.05). With 7 days recovery, basal glycoprotein secretion (predominantly sulfated) was greatly increased above control, while the increased net secretion of Cl- and of water persisted (P less than 0.05). Histology of the airways indicated that acute exposure induced moderate hypertrophy of submucosal glands in the lower trachea (P less than 0.05), while chronic exposure (with and without recovery) induced a large hypertrophy of submucosal glands in both upper and lower trachea (P less than 0.05). Without recovery, however, the gland cells were devoid of secretory material, whereas with recovery they were full of secretory material. This suggests that the decreased glycoprotein secretion with chronic exposure alone resulted from incomplete replenishment of intracellular stores after 6 wks of stimulation. We conclude that both short- and long-term O3 exposure causes airway-mucus hypersecretion.

Animals↗
PubMed1984

Control of nasal vasculature and airflow resistance in the dog.

Nasal vascular and airflow resistances have been measured in dogs, simultaneously on both sides separately. Vascular resistance was measured either by constant flow perfusion of the terminal branch of the maxillary artery (which supplies, via the sphenopalatine artery, the nasal septum, most of the turbinates and the nasal sinuses) or by measuring blood flow through this artery, maintained by the dog's own blood pressure. Airflow resistance was assessed by inserting balloon-tipped endotracheal catheters into the back of each nasal cavity via the nasopharynx, and measuring transnasal pressure at constant airflow through each side of the nose simultaneously. Preliminary experiments indicated that there was 5-10% collateral anastomosis between the two sides. Close-arterial injection of drugs showed different patterns of response. Adrenaline, phenylephrine, chlorpheniramine and low doses of prostaglandin F2 alpha increased vascular resistance and lowered airway resistance. Salbutamol, methacholine and histamine lowered vascular resistance and increased airway resistance. Dobutamine decreased airway resistance with a small increase in vascular resistance. Prostaglandins E1, E2 and F2 alpha (high dose) decreased both vascular and airway resistances. Substance P, eledoisin-related peptide and vasoactive intestinal polypeptide lowered vascular resistance with little change in airway resistance. The results are interpreted in terms of possible drug actions on precapillary resistance vessels, sinusoids and venules, and arteriovenous anastomoses. It is concluded that nasal airway resistance cannot be correlated with vascular resistance or blood flow, since the latter has a complex and ill-defined relationship with nasal vascular blood volume.

Adrenergic Agonists↗