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Biomedical subjects

R J Phipps

Publications and source records attributed to R J Phipps.

At least 19 recordsLinked to original sources
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↗
PubMed1984

Control of mucoglycoprotein output from the rabbit nose.

A method for the collection of rabbit nasal washings to analyse outputs of mucous glycoproteins is described. The radiolabels sodium [35S]sulphate and [3H]glucose are bound to the glycoproteins. The release of bound 35S and 3H was enhanced by cervical sympathetic nerve stimulation. Adrenoceptor agonists (phenylephrine, dobutamine and salbutamol) given I.V. increased the output of 35S, and the last two drugs increased the output of 3H. The blocking effects of thymoxamine and propranolol on these responses are described. Pilocarpine (given I.V. or intranasally) produced large increases in 35S release; histamine had little effect. Irritants (ammonia and cigarette smoke) and diluted serum or plasma, given intranasally, produced large increases in 3H output, and sometimes enhanced 35S release. Radiolabelled nasal washings fractionated on Sepharose CL-4B gel chromatography columns formed two peaks, with most of the radioactivity in the high molecular weight (mucous glycoprotein) peak.

Adrenergic beta-Agonists↗
PubMed1984

A preparation for the study of secretory function of the human bronchus in vitro.

Bronchi, not involved in tumor, were removed from resected human lungs. They were mounted in Ussing chambers containing Krebs-Henseleit solution with radiolabelled precursors of mucus. Airway was examined by both light and electron microscopy. Tissues recently removed from resected lungs exhibited both intra- and extra-cellular oedema and hypoxic changes in mitochondria, but tight junctions between epithelial cells appeared intact, indicating an effective epithelial barrier. Tissues removed from Ussing chambers after up to 6 h showed little oedema and their mitochondria were normal. Their appearance had returned to that of specimens taken that biopsy and fixed immediately. Autoradiographs of specimens from Ussing chambers showed that the mucus-producing cells had concentrated the radiolabels . Mucus in gland ducts was also radiolabelled. Damaged areas of mucous membrane were rare and probably pre-operative. We conclude that resected bronchi, suspended in Ussing chambers, have a structure and secretory activity suitable for investigations of the control of secretion.

Autoradiography↗
PubMed1983

Antigen stimulates glycoprotein secretion and alters ion fluxes in sheep trachea.

We studied the effects of in vitro challenge with specific antigen (Ascaris suum antigen) on glycoprotein secretion and ion fluxes in tracheal tissues from allergic sheep. We mounted tissues in Perspex chambers and measured secretion of 35S- and 3H-labeled glycoproteins and fluxes of Cl- and Na+. In tissues from allergic sheep, A. suum antigen (25 micrograms protein X ml-1) increased glycoprotein secretion. A. suum antigen initially reversed net Cl- flux, causing net absorption of Cl- and of Na+. This was followed 15-30 min later by net secretion of Cl- and of Na+. Pretreatment of tissues with cromolyn (10(-4) M) greatly reduced the effects of A. suum antigen but did not abolish them. The cromolyn-resistant effects were nonspecific, because they were similar to those of in vitro challenges with nonspecific proteins, ovalbumin and ragweed in allergic sheep, and A. suum antigen in nonallergic sheep. We conclude that challenge with A. suum antigen results in mucus hypersecretion in airways of allergic sheep, by both specific and smaller nonspecific effects. Specific effects (cromolyn sensitive) are produced by mediators which are released from airway cells in response to A. suum challenge.

Animals↗
PubMed1982

Sympathomimetic drugs stimulate the output of secretory glycoproteins from human bronchi in vitro.

1. We describe a method for supporting pieces of human bronchi in Ussing chambers, for radiolabelling the contents of the secretory cells with 35S, and for collecting radiolabelled macromolecules secreted on to the luminal aspect of the tissue. This method has previously been used to study airway secretions in animals [R. J. Phipps, J. A. Nadel & B. Davis, American Review of Respiratory Disease, (1980) 121, 359-365]. Evidence is given that the radiolabelled molecules are secretory glycoproteins, probably mucus glycoproteins. 2. Phenylephrine, an alpha-adrenoceptor agonist, increased the rate at which the bronchi secreted radiolabelled glycoproteins. Thymoxamine, an alpha-adrenoceptor antagonist, blocked this effect but propranolol, a beta-adrenoceptor antagonist, did not. 3. Dobutamine, a beta-adrenoceptor agonist, increased the rate of secretion of radiolabelled glycoproteins. Propranolol blocked this but thymoxamine did not. 4. Salbutamol, a beta 2-adrenoceptor agonist, also increased the rate of secretion of radiolabelled glycoproteins. Propranolol blocked this effect. 5. We conclude that both alpha- and beta- adrenoceptor agonists increase the rate of glycoprotein secretion in human bronchi in vitro and that this almost certainly means that they increase the rate of mucus secretion.

Autoradiography↗