Biomedical subjects

E R Walker

Publications and source records attributed to E R Walker.

At least 19 recordsLinked to original sources

PubMed1993

Disturbed gastric emptying in the short bowel syndrome. Evidence for a 'colonic brake'.

Gastric emptying of liquid (orange juice containing technetium-99m (99mTc) labelled antimony sulphide colloid) and solid (570 kcal pancake containing 0.5 mm resin microspheres labelled with Indium-111 (111-In)) was measured in seven patients with jejunum and no colon (jejunal lengths 30-160 cm), six patients with jejunum in continuity with the colon (jejunal length 25-75 cm), and in 12 normal subjects. In patients with no colon early emptying of liquid was rapid (median 25% emptying: 7 v 25 min, no colon v normal, p < 0.05); early gastric emptying of solid was rapid in two (each with less than 100 cm jejunum) and normal in the other five. Gastric emptying of liquid and solid for patients with jejunum in continuity with the colon was normal for the first three hours. There was increased liquid and solid retained in the stomach at six hours in both groups of patients (p < 0.01). Small bowel transit time was faster than in normal subjects for liquid in both groups of patients (p < 0.05) and for solid in those with no colon (p < 0.05). Rapid gastric emptying of liquid may contribute to the large stomal output in patients with a high jejunostomy. Preservation of the colon after a major small intestinal resection exerts a braking effect on the rate of early gastric emptying of liquid.

Adult↗

PubMed1992

Methoxytetrahydropyrans. A new series of selective and orally potent 5-lipoxygenase inhibitors.

Investigation of the SAR of the lead (methoxyalkyl)thiazole 1-[3-(naphth-2-ylmethoxy)phenyl]-1-thiazol-2-ylprop yl methyl ether (1, ICI 211965) led to the methoxytetrahydropyrans, a new series of 5-lipoxygenase (5-LPO) inhibitors exemplified by the parent compound 4-[3-(naphth-2-ylmethoxy)phenyl]-4- methoxy-3,4,5,6-tetrahydro-2H-pyran (4f). In vitro 4f inhibited leukotriene C4 (LTC4) synthesis in zymosan-stimulated plasma-free mouse macrophages and LTB4 synthesis in A-23187-stimulated human whole blood (IC50s 0.5 nM and 0.07 microM, respectively). In the rat 4f inhibited LTB4 synthesis in blood ex vivo and in zymosan-inflamed air pouch exudate with an ED50 3 h after oral dosing of 10 mg/kg in each system. In seeking more potent orally active compounds, strategies were explored in congeners of 4f for reducing lipophilicity without sacrificing potency. For example, replacement of 2-naphthyl of 4f by various aza- and oxoheterocycles afforded compounds in which log P is reduced by 1.7-2.3 units while potency in human whole blood in vitro was maintained or enhanced relative to 4f. In addition, the oxoheterocyclic replacements provided compounds with improved oral potency and the preferred compound from this group is 6-[[3-fluoro-5-(4-methoxy-3,4,5,6-tetrahydro-2H-pyran-4- yl)phenoxy]methyl]-1-methylquinol-2-one (4y). In the in vitro systems, 4y inhibited LT formation with IC50s in mouse macrophages and human whole blood of 3 nM and 0.02 microM, respectively. 4y did not inhibit the synthesis of cyclooxygenase (CO) products at concentrations up to 500 microM in human blood, a selectivity for 5-LPO over CO of greater than 20,000-fold. In the rat 4y inhibited the formation of LTB4 in blood ex vivo and in inflammatory exudate with ED50s 3 h after oral dosing of 0.9 and 0.3 mg/kg, respectively. 4y was more potent in vitro in human whole blood and in rat blood ex vivo at 3 h than either the 5-LPO inhibitor A-64077 or the FLAP antagonist MK-886. Based on these data 4y (ICI D2138) has been entered into development as an orally active, selective 5-LPO inhibitor for clinical evaluation in inflammatory conditions in which LTs are believed to play a role.

Administration, Oral↗

PubMed1992

Designing therapeutically effective 5-lipoxygenase inhibitors.

Metabolism of arachidonic acid by the enzyme 5-lipoxygenase leads to the formation of a group of biologically active lipids known as leukotrienes. Peptidoleukotrienes are powerful bronchoconstrictor agents while leukotriene B4 is a potent chemotactic agent for a variety of leukocytes. In view of these properties, leukotrienes have been proposed as important mediators in allergic and inflammatory disorders, and inhibitors of 5-lipoxygenase, by blocking leukotriene synthesis, have therapeutic potential in a range of diseases including arthritis and asthma. This review by Rodger McMillan and Ed Walker summarizes the biology of leukotrienes and the current knowledge of the mechanism of 5-lipoxygenase, providing a framework for consideration of the discovery, development and clinical status of drugs in the three major classes of 5-lipoxygenase inhibitors: 'redox' inhibitors, iron ligand inhibitors and 'non-redox' inhibitors.

Animals↗

PubMed1992

A patient with jejunostomy liberated from home intravenous therapy after 14 years; contribution of balance studies.

A patient with a jejunostomy 100 cm from the duodeno-jejunal flexure, following surgery for Crohn's disease, had needed parenteral fluids at home for 14 years because of a negative intestinal balance of sodium. Measurements were made of her oral intake and intestinal output during study periods each of 2 days. Loperamide 4 mg QDS, codeine phosphate 60 mg QDS and both together put her into positive intestinal fluid balance but sodium balance remained negative. Both drugs used together were more effective than either used alone. Ranitidine 300 mg BD made no significant difference to her intestinal output. 1 litre of a glucose-electrolyte solution (120 mmol sodium) sipped during the day resulted in sodium balance, but only with the addition of loperamide and codeine phosphate was positive sodium balance achieved (mean 44 mmol/day). This therapy allowed her to dispense with parenteral fluids which have been stopped for the last year.

Journal Article↗

PubMed1992

Pre-clinical pharmacology of ICI D2138, a potent orally-active non-redox inhibitor of 5-lipoxygenase.

1. This paper describes the pre-clinical pharmacology of ICI D2138, a potent orally-active non-redox inhibitor of 5-lipoxygenase which is undergoing clinical evaluation. 2. ICI D2138 potently inhibited leukotriene synthesis in murine peritoneal macrophages (IC50 = 3 nM) and human blood (IC50 = 20 nM). In human and dog blood, ICI D2138 did not inhibit thromboxane B2 synthesis at a concentration of 500 microM, thus the selectivity ratio (cyclo-oxygenase: 5-lipoxygenase) was greater than 20,000. In contrast, zileuton (a 5-lipoxygenase inhibitor also undergoing clinical evaluation) exhibited a selectivity ratio of 15-100. 3. ICI D2138 potently and dose-dependently inhibited ex vivo leukotriene B4 (LTB4) synthesis by rat blood with ED50 values of 0.9, 4.0 and 80.0 mg kg-1 p.o. at 3, 10 and 20 h respectively after dosing. Similar activity was observed for inhibition of LTB4 production in a zymosan-inflamed rat air pouch model. Zileuton produced ED50 values of 5 and 20 mg kg-1 at 3 and 10 h respectively. 4. Oral administration of 1, 3 or 10 mg kg-1 ICI D2138 to dogs produced maximal inhibition of ex vivo LTB4 synthesis by blood for 5, 9 and 31 h respectively. A dose of 5 mg kg-1 p.o. of zileuton caused maximal inhibition of LTB4 for 24 h. 5. Oral administration of 10 mg kg-1 ICI D2138 caused total inhibition of LTB4 production in zymosan-inflamed rabbit knee joint. 6. Topical administration of ICI D2138 to rabbit skin caused a dose-related inhibition of arachidonic acid-induced plasma extravasation with an ID30 of 1.08 nmol per site. Zileuton was approximately 40 times less potent.7. Oral anti-inflammatory activity was assessed in an arachidonic acid-induced mouse ear oedema model in animals treated with indomethacin to block pro-inflammatory prostanoids. ICI D2138, given orally, caused dose-dependent inhibition of oedema with an approximate ID50 of 1.8 mg kg'. Zileuton was approximately 10 times less potent.8. ICI D2138 caused a dose-dependent inhibition of antigen-induced broncho-constriction in guineapigs with an approximate ID50 of 0.1 mg kg-', i.v. Zileuton was approximately 10 times less potent.9. In view of the pharmacological profile described here, ICI D2138 has the potential to provide improved clinical efficacy compared to existing lipoxygenase inhibitors such as zileuton.

Administration, Oral↗

PubMed1992

Oral salt supplements to compensate for jejunostomy losses: comparison of sodium chloride capsules, glucose electrolyte solution, and glucose polymer electrolyte solution.

Six patients with jejunostomies and residual jejunal lengths of 105 to 250 cm took the same food and water each day for eight study days. In random order, three methods of salt replacement were tested, each over 48 hours, against a period without added salt. During the three test periods the patients took 120 mmol of sodium chloride daily, as salt in gelatine capsules, as an isotonic glucose electrolyte (280 mOsmol/kg; 30 kcal) solution, and as a glucose polymer (Maxijul) solution (280 mOsmol/kg; 200 kcal). The daily stomal output remained constant for each patient during the four test periods but varied between patients from 0.60 to 2.84 kg (daily intestinal fluid balance 0.74-2.61 kg). Without a salt supplement, three patients lost more sodium from the stoma than they took in by mouth (-25, -94, and -101 mmol/day) and the mean sodium balance for all six subjects was -16 mmol (range -101 to 79) daily. Extra salt was absorbed with each form of supplement (p less than 0.05); no patient with the glucose electrolyte solution (mean 96, range 0 to 226 mmol), but one patient with the glucose-polymer solution (mean 96, range -25 to 164 mmol) and two with the salt capsules (mean 66, range -8 to 145 mmol) were in negative balance. Two patients vomited with the salt capsules. There was only a small increase in energy absorption (mean 115 kcal) with the glucose polymer solution compared with the glucose electrolyte solution. A sipped glucose electrolyte solution seems to be the optimal mode of sodium replacement in patients with a high output jejunostomy.

Adult↗

PubMed1992

Modulation of human upper intestinal nutrient transit by a beta adrenoreceptor mediated pathway.

To explore the role played by beta adrenoreceptor mediated pathways on human upper gut function a series of studies were conducted into the effects of beta adrenoreceptor agonists and antagonists on orocaecal and duodenocaecal transit and on antral and duodenal motor activity. Under control conditions orocaecal transit was consistent within individuals (mean coefficient of variation (18.0%) but varied widely between individuals (median transit 63 minutes, range 33-164). Prior administration of the non-selective beta adrenergic antagonist propranolol consistently hastened orocaecal transit (median transit 51:25-93, v control p < 0.005). The selective beta-1 antagonist, atenolol, also hastened transit (median transit 50:35-93 minutes, v control p < 0.01). The magnitude of an individual's response to beta blockade correlated closely with the orocaecal transit (Tau = 0.54, p < 0.01). Duodenocaecal transit was also hastened by propranolol from control values of 66:45-107 minutes to 50:16-62 minutes, p < 0.025). In contrast neither duodenal nor antral motility were consistently altered by beta blockade. The beta adrenoreceptor agonist, isoprenaline, delayed both orocaecal transient (97:55-178 minutes, v control p < 0.005) and also duodenocaecal transit (160:45-215 minutes, v 73:40-133) (p < 0.025). Isoprenaline also reduced antral motility by an effect which appeared to occur predominantly through a reduction in contraction amplitude (from a median amplitude of 27:5.39 mm Hg to 14:3-24 mm Hg, p < 0.03) rather than an effect on the interval between contractions. No effect on either amplitude or frequency of duodenal motor activity was observed. A beta adrenoreceptor mediated pathway thus appears to exert a biologically relevant effect on gut function not only under conditions of sympathetic stimulation, but also at rest when a basal beta adrenergic tone appears to influence the speed of nutrient transit through the human upper gut.

Adult↗

PubMed1991

Morphologic and morphometric changes in synovial membrane associated with mechanically induced osteoarthrosis.

We sought to determine whether synovial leukocytic inflammation is a primary event in mechanically induced osteoarthrosis. Repetitive impulse loading (50 ms duration at 60 Hz for 40 minutes each day) was applied to the right hindlimbs of 24 New Zealand white rabbits for 3, 6, or 9 weeks. The synovial membrane from the medial suprapatellar area was examined qualitatively using transmission electron microscopy and quantitatively using light microscopic morphometry. The results indicate that synovial inflammation is not a primary event in this mechanically induced osteoarthrosis, but synovial hyperplasia occurs prior to histologically evident cartilage destruction at 6-9 weeks.

Animals↗

PubMed1991

Effect of omeprazole on intestinal output in the short bowel syndrome.

Ten patients with an end jejunostomy and one with a jejuno-rectal anastomosis (jejunal length 30-140 cm) ate a constant chosen diet for 2 control days, and 2 test days when 40 mg omeprazole orally was taken each morning. In the 7 patients with a net secretory output of fluid, there was a mean reduction in wet weight of 0.66 kg/24 h (range -0.16 to 1.45 kg/24 h; P less than 0.05) and sodium 46 mmol/24 h (-51 to 135 mmol/24 h; N.S.); the four patients with net absorption of fluid showed no reduction in intestinal output. One patient with 30 cm jejunum responded little to oral but did so to intravenous 40 mg omeprazole twice a day with a reduction in wet weight of 3.00 kg/24 h and sodium 157 mmol/24 h. In one patient oral 40 mg omeprazole daily gave equivalent results to oral 300 mg ranitidine twice daily; in 2 others it was equivalent to intravenous 50 micrograms octreotide twice daily. Omeprazole reduces the intestinal output in patients with the short bowel syndrome and a net secretory output, but not enough to prevent the need for parenteral fluid and electrolyte replacement.

Anastomosis, Surgical↗

PubMed1990

Jejunal efflux in short bowel syndrome.

24 h oral intake and intestinal output were studied in 15 patients with a short residual length of jejunum and no colon. 8 patients showed a net secretory, and 7 a net absorptive response to food. In secretors, daily intestinal output exceeded oral intake (mean 2.3 kg wet weight, and 233 mmol sodium). Long-term parenteral fluid and electrolyte replacements were needed only in those with a secretory response. Jejunal length inversely correlated with net intestinal output of fluid, sodium, potassium, and with percentage energy absorption. A secretory response was observed if jejunal length was less than 100 cm and was reduced by gastric antisecretory drugs and octreotide.

Administration, Oral↗

PubMed1990

Surface characteristics, morphology, and ultrastructure of human adherent lymphokine-activated killer cells.

Human adherent lymphokine-activated killer (A-LAK) cells represent a population of highly cytotoxic, interleukin-2 (IL-2)-activated peripheral blood lymphocytes that have large granular lymphocyte (LGL) morphology and display natural killer (NK) cell-associated surface markers (CD3-CD56+). The ultrastructure of A-LAK cells also is consistent with that of highly activated NK cells. After their initial isolation, continued culture of A-LAK cells in the presence of IL-2 resulted in cyclic shifts between adherent and non-adherent phases with about 90% of the cells floating and non-adherent. All of these A-LAK cells were spheroidal with numerous villi and pseudopodia. In the adherent phase, A-LAK cells were motile, moving along the solid surface at a speed of about 1 micron per minute, and polar, with a ruffled leading edge at one end of the cell and a terminal tuft of villi at the opposite end. Transmission electron microscopy of these cells also demonstrated a high degree of internal polarity, with the nucleus at the leading edge of the cell and richly granulated cytoplasm at the terminal end. Extensive cytoskeletal structures, multivesicular bodies, and an active Golgi complex characterized these cells. A-LAK cells in the adherent phase were found to express numerous point contacts (podosomes) and larger adherence structures containing polymerized actin, which appear to be important for interactions of these cells with the substrate. Increased expression of adhesion molecules in association with surface structures mediating adherence is also responsible for effective binding of A-LAK cells to solid surfaces.

CD18 Antigens↗

PubMed1990

2-substituted indazolinones: orally active and selective 5-lipoxygenase inhibitors with anti-inflammatory activity.

1. This paper describes the pharmacological profile of ICI207968, a novel, orally-active and selective inhibitor of 5-lipoxygenase. 2. Inhibition of leukotriene B4 (LTB4) synthesis by 2-substituted indazolinones was not directly related to redox potential but was critically dependent on the nature of the N2 substituent. 2-(3-Pyridylmethyl)-indazolinone (ICI207968) combined selectivity and oral potency. 3. In several in vitro systems ICI207968 exhibited similar lipoxygenase inhibitory potency (IC50 values from 1.5 microM to 6.0 microM) and was approximately 300 times less potent against cyclo-oxygenase, as measured by inhibition of prostaglandin E2 (PGE2) synthesis. 4. ICI207968 also produced selective lipoxygenase inhibition following oral administration in the rat. ED50 values of 2.5, 10 and 25 mg kg-1 p.o. for inhibition of LTB4 release from A23187-stimulated blood were obtained 1, 3 and 5 h after dosing. The compound did not inhibit PGE2 synthesis at oral doses up to 300 mg kg-1. 5. Co-administration of ICI207968 with arachidonic acid, into rabbit dermis, potently inhibited both plasma extravasation and polymorphonuclear leucocyte (PMNL) infiltration induced by this inflammatory fatty acid. The anti-inflammatory potency of a number of intradermally administered indazolinones, with similar redox potentials, was related to their inhibitory potency against leukotriene generation in blood. Oral administration of ICI207968 (100 mg kg-1) in the rabbit inhibited ex vivo leukotriene generation in blood and arachidonic acid-induced skin inflammation. 6. These data demonstrate that ICI207968 is an orally active and selective inhibitor of 5-lipoxygenase which has anti-inflammatory properties. IC1207968 will be a valuable agent for clarifying the biological roles of leukotrienes and the therapeutic potential of 5-lipoxygenase inhibitors.

Administration, Oral↗

PubMed1990

Short bowel syndrome.

Nine patients with short bowel syndrome and high intestinal output received octreotide either intravenously (50-100 micrograms t.i.d.) or subcutaneously (100 micrograms b.i.d.) on 2 test days. In the 6 patients with net secretory output, there was a reduction in mean daily intestinal output of 0.5-5.0 kg; total daily intestinal output of sodium and potassium was also reduced significantly. Of the 3 patients with a net absorptive state, there was a worsening of output in 2 and no improvement occurred in the other. Two patients with net secretory output received long-term octreotide therapy, allowing a reduction in daily intravenous fluid intake of 1.0-1.5 litres.

Administration, Oral↗

PubMed1989

Octreotide (a somatostatin analogue) improves the quality of life in some patients with a short intestine.

Six patients with short intestine (jejunal length 25-70 cm) on long-term parenteral nutrition, needing 4-5 L of intravenous fluid daily, were given octreotide (a somatostatin analogue, SMS 201-995) to investigate whether it would reduce beneficially their secretory diarrhoea (3.6-6.9 kg/day). They consumed the same diet for 2 control days, followed by 2 test days. Octreotide was given intravenously, initially in a dose of 50 micrograms b.d. through the central feeding line. There was a significant reduction of daily stomal output (0.5-5.0 kg) and daily sodium and potassium output; however there was no significant change in energy absorption. The response to octreotide was greatest in those patients who absorbed least nutrients. A dose increase to 100 micrograms t.d.s. gave no further measurable benefit though the patients found it smoothed-out the post-prandial rise in stomal output. Two patients were continued on long-term octreotide therapy, which allowed for a daily reduction in intravenous fluid of 1 and 1.5 L. Octreotide's anti-secretory effect was found to have been maintained when it was retested in one patient after a year of continuous therapy.

Diarrhea↗

PubMed1989

Scleromyxedema serum increases proliferation but not the glycosaminoglycan synthesis of dermal fibroblasts.

In comparison to normal fibroblasts cultured in parallel, scleromyxedema fibroblasts grew less well, synthesized increased amounts of glycosaminoglycans (GAG) in vitro and had ultrastructural abnormalities. Serum obtained from a patient with scleromyxedema increased in vitro fibroblast proliferation but not the GAG synthesis per cell. Serum obtained after therapy, at the time when clinical improvement was observed, continued to stimulate fibroblast proliferation. Thus the serum factor stimulating the fibroblast proliferation did not modulate their GAG synthesis and had no direct relationship to disease activity.

Female↗

PubMed1989

The mineralization of elastic fibers and alterations of extracellular matrix in pseudoxanthoma elasticum. Ultrastructure, immunocytochemistry, and X-ray analysis.

Histologic paraffin sections of pseudoxanthoma elasticum (PXE)-involved skin of forearm and axilla were used for histochemistry and immunohistochemical and analytical electron microscopy to study the progressive mineralization in the dermis of patients with PXE. The von Kossa technique identified mineral deposits throughout the reticular PXE dermis. X-ray analysis revealed patterns of calcium and phosphorus deposition in the von Kossa-positive areas, and the immunohistochemical staining using monoclonal antibodies identified increased chondroitin-6-sulfate in these areas when compared with normal skin. Scanning transmission electron microscopy observation combined with X-ray dot mapping show calcium and phosphorus to be codistributed within the mineralized area. This study confirms by new methods the increase in chondroitin-6-sulfate, alterations in elastin and collagen, and a high calcium and phosphorus elemental distribution matching the mineralized area in the PXE dermis.

Calcium↗

PubMed1988

Scleromyxedema myopathy: case report and review of the literature.

We describe a patient who had scleromyxedema associated with proximal myopathy. The histopathologic and electron microscopic features are presented. In addition, we review the clinical and pathologic features of all 9 previously reported patients with documented scleromyxedema and myopathy. Proximal (pharyngeal) or distal dysphagia (7 of 7 patients), elevated creatine kinase (5 of 8), elevated aldolase (3 of 3), and electromyographically demonstrated myopathy (7 of 7) were usual features. Four patients had muscle biopsies that showed myofibril vacuolar changes, but inflammation was infrequent (2 cases). Our patient responded to oral prednisone and weekly intravenous methotrexate with improvement of the erythroderma, papular rash, and muscle strength.

Arm↗

PubMed1988

Amiodarone-induced phospholipidosis in rat alveolar macrophages.

Humans treated with the antiarrhythmic drug amiodarone may develop pulmonary toxicity accompanied by the presence of alveolar macrophages (AM) containing lamellar inclusions. This cellular response is indicative of the development of a drug-induced phospholipidosis. To characterize this response of the AM, Fischer-344 rats were treated with amiodarone, and the macrophages were recovered by pulmonary lavage. The development of phospholipidosis was dose- and time-dependent and was reversible. Daily treatment for 1 wk (5 days/wk) at 150 mg/kg resulted in a 5-fold increase in total phospholipid in the cells. Phospholipid levels were increased only slightly more through 9 wk of treatment. Cells were filled with lamellar inclusions and contained areas of amorphous granular and membranous material. Individual classes of phospholipids were all increased during the development of phospholipidosis. When expressed as mumol/10(7) cells, phosphatidylcholine demonstrated the largest increase. Levels of amiodarone and its major metabolite, desethylamiodarone, increased in AM in parallel with the increase in phospholipid. From 3 days through 9 wk of treatment, the level of desethylamiodarone was always higher than that of amiodarone. Treatment with desethylamiodarone also induced phospholipidosis in AM. Administration of phenobarbital along with amiodarone for 1 wk caused a reduction in the levels of amiodarone, desethylamiodarone, and phospholipid in the cells. The molar ratio of amiodarone to phospholipid was decreased, whereas the molar ratio of desethylamiodarone to phospholipid remained unchanged. Taken together, the results indicate that, along with amiodarone, desethylamiodarone and/or its metabolites may play an important role in the phospholipidosis induced in AM when rats are treated with amiodarone.

Amiodarone↗