The Effect of Omeprazole Pre-treatment on Rafts Formed by Reflux Suppressant Tablets Containing Alginate

Alginate-based reflux suppressant preparations provide symptom relief by forming a physical barrier on top of the stomach contents in the form of a neutral floating gel or raft. This study investigated whether reduced acidity in the stomach brought about by omeprazole pre-treatment affected the formation and gastric residence time of alginate rafts. It was a balanced, cross-over study in 12 healthy non-patient volunteers following a single dose of two indium-111-labelled alginate tablets in the presence or absence of 3 days' pre-treatment with omeprazole. Raft formation and gastric residence, in the presence of a technetium-99m-labelled meal, were assessed by gamma scintigraphy for 3 h after alginate tablet administration. The relative raft-forming ability of alginate tablets after omeprazole compared with alginate tablets alone was 0.950 with 95% confidence intervals of 0.882 and 1.018. Pre-treatment and co-administration with omeprazole has no significant effect on the raft-forming ability of alginate tablets.

Bowel habit, diet and body weight in preadolescent children

BACKGROUND

The possible influence of diet and body weight on bowel habit in children is unknown. The present study aimed to investigate the inter-relationships between bowel function, excess body weight and dietary intake in a group of preadolescent children.

METHODS

Eighty-four preadolescent children aged 7-10 years were recruited [mean (SD) age 9.7 (1.0) years]. All children completed a bowel habit diary, examining specific parameters of bowel function and a weighed food inventory concurrently for seven consecutive days. Height and weight measurements were also taken. Children were grouped according to whether they met dietary recommendations and by overweight status; differences in bowel function between the groups were then analysed.

RESULTS

Children who exceeded reference values for fat were more likely to report an incidence of straining to start (P = 0.005) and pain during defaecation (P = 0.021). Subjects who met protein recommendations were less likely to report incomplete evacuation (P = 0.000) and those who met zinc recommendations were less likely to report pain during defaecation (P = 0.044). Excess body weight (according to International Obesity Task Force cut-offs) was also associated with poor bowel habit, with overweight and obese children reporting lower defaecation frequency and a higher incidence of straining and feelings of incomplete evacuation, although these findings were not statistically significant. Defaecation frequency in healthy children was 1.4 defaecations per day compared to 1.2 defaecations for overweight and obese children.

CONCLUSION

A poor diet that fails to meet dietary recommendations as well as being overweight and obese appears to be associated with increased defaecation problems in preadolescent children.

The online Cough Clinic: developing guideline-based diagnosis and advice

The aim of the present study was make chronic cough guidelines more practical and user friendly by developing an internet-based interactive diagnostic questionnaire for chronic cough. A prospective cohort study of chronic cough sufferers was conducted in the UK, following European Respiratory Society guidelines for the diagnosis and management of chronic cough. Depending on the response to 16 specific questions, the medical condition responsible for the patient's chronic cough was ascertained according to a predetermined diagnostic algorithm designed to differentiate the three common causes of chronic cough. Appropriate advice and treatment recommendations were then provided. 8,546 adults with chronic cough completed the Cough Clinic diagnostic questionnaire. 46.1% were suggested to have reflux, 38.7% asthma and 15.2% rhinitis. Participants found the website easy to use (94%), the advice helpful (73%) and that it helped them to communicate with their general practitioner better (60%), and 62% reported taking the recommended treatment. The Cough Clinic, an internet-based diagnostic site for chronic cough, had a large uptake by chronic cough sufferers in the UK. Almost half were diagnosed as having reflux as the probable cause of their chronic cough. Internet diagnosis by expert algorithm provides a novel mechanism for patients to access guideline-recommended therapies and enhances dialogue between patients and physicians.

Habitual micronutrient intake during and after pregnancy in Caucasian Londoners

Micronutrient status is of fundamental importance both upon conception and throughout pregnancy. There is an abundance of literature investigating nutrient intakes during individual trimesters of pregnancy but few studies have investigated baseline intakes of nutrients throughout gestation as a continuum. The current investigation set out to measure habitual micronutrient intakes at weeks 13, 25, 35 of pregnancy and 6 weeks postpartum using a prospective background information questionnaire, 4-7-day weighed food diary and postnatal questionnaire. Seventy-two primiparous, Caucasian Londoners were recruited at the study start with 42 completing the first, second, third trimester and postpartum study stages respectively. Study findings indicated that sodium intakes were significantly higher than UK guidelines throughout and after pregnancy (P < 0.001). Intakes of folate, iron, vitamin D, potassium, iodine and selenium were lower than UK recommendations during and after pregnancy, but to varying levels of statistical significance (P < 0.05). Only 23-38% of women met UK recommendations for folate (300 microg day(-1)) through dietary sources. Similarly, only a small percentage of women met dietary guidelines for iron (19-28%). The findings from the current study indicate that public health interventions may be required to help expectant mothers achieve an optimal diet, particularly after birth when dietary recommendations increase for some micronutrients.

Daily ingestion of alginate reduces energy intake in free-living subjects

Sodium alginate is a seaweed-derived fibre that has previously been shown to moderate appetite in models of acute feeding. The mechanisms underlying this effect may include slowed gastric clearance and attenuated uptake from the small intestine. In order to assess whether alginate could be effective as a means of appetite control in free-living adults, 68 males and females (BMI range: 18.50-32.81 kg/m(2)) completed this randomised, controlled two-way crossover intervention to compare the effects of 7 day daily ingestion of a strong-gelling sodium alginate formulation against a control. A sodium alginate with a high-guluronate content was chosen because, upon ingestion, it forms a strong gel in the presence of calcium ions. Daily preprandial ingestion of the sodium alginate formulation produced a significant 134.8 kcal (7%) reduction in mean daily energy intake. This reduced energy intake was underwritten by significant reductions in mean daily carbohydrate, sugar, fat, saturated fat and protein intakes. The absence of any significant interaction effects between the main effect of preload type and those of gender, BMI classification and/or timing of preload delivery indicates the efficacy of this treatment for individuals in different settings. These findings suggest a possible role for a strong-gelling sodium alginate formulation in the future management of overweight and obesity.

Thickness and continuity of the adherent colonic mucus barrier in active and quiescent ulcerative colitis and Crohn's disease

BACKGROUND

The colon is covered by a mucus barrier that protects the underlying mucosa and alterations in this mucus barrier have been implicated in the aetiology of inflammatory bowel disease (IBD). This study investigated the thickness and continuity of the mucus barrier in ulcerative colitis (UC) and Crohn's disease (CD) in comparison to normal controls.

METHODS

Rectal biopsies were taken from 59 patients and cryostat sections stained with periodic acid-Schiff's/Alcian blue to visualise the mucus layer. Mucus thickness and continuity and goblet cell density were measured using light microscopy.

RESULTS

An essentially continuous adherent mucus layer was observed in normal human rectum and there was no change in the mucus barrier in quiescent UC. In active UC there was a trend for the mucus layer to become progressively thinner and significantly more discontinuous as disease severity increased. In severe active UC the mucus layer thickness and goblet cell density were significantly reduced compared with normal controls while the percentage discontinuity significantly increased.

CONCLUSION

It is not until severe UC that there is a global change in mucosal protection as a consequence of large regions lacking mucus, a decrease in secretory potential caused by a loss of goblet cells and a thinner, less effective mucus layer even when it is present.

The suppression of gastro-oesophageal reflux by alginates

AIMS

The aim of this study was to compare alginate products with the same amount of active ingredients but different dosage forms, in the suppression of reflux provoked by a standard meal in healthy human volunteers, using ambulatory oesophageal pH monitoring.

METHODS

This was a single centre, randomised, open, three-period crossover, controlled study comparing Gaviscon Advance (10 ml) with a control (10 ml water) and with a new tablet product containing the same active ingredients as Gaviscon Advance. Volunteers who had oesophageal pH < 4 for at least 2% of the 4-h period after ingestion of a test meal followed by control at a reflux screening visit were included in the study.

RESULTS

The difference between Gaviscon Advance and control in the mean angular transformed percentage of time for which oesophageal pH fell below four was statistically significant (p < 0.0001) demonstrating the sensitivity of the method. No significant difference between the two alginate products was found based on the least squares adjusted mean angular transformed percentage of time for which pH fell below four. There were also no significant differences between the two alginate dosage forms in the angular transformed percentage of time for which oesophageal pH fell below five and in the log-transformed number of occasions on which oesophageal pH fell below four and five.

DISCUSSION AND CONCLUSION

The study shows that alginate reflux suppressants containing a low amount of antacid are effective in suppressing acid reflux and that suspension and tablet forms are able to give equivalent acid suppression.

Administration of an alginate based gastric reflux suppressant on the bioavailability of omeprazole

BACKGROUND & OBJECTIVE

Omeprazole treats gastro-oesophageal reflux disease (GORD) by inhibition of acid secretion whereas alginate based reflux suppressants work by forming a low density raft of near neutral pH which floats on the stomach contents and physically impedes gastro-oesophageal reflux. There is limited pharmacokinetic information regarding possible drug interaction between these two types of products, although these may be frequently co-prescribed to improve symptom control in GORD patients. This study was designed to determine whether the administration of a 10 per cent w/v liquid alginate suspension affected the pharmacokinetic profile of omeprazole.

METHODS

This was a randomized, two-treatment, two-sequence, two-period crossover study in 26 volunteers. Each treatment was dosed for 3 consecutive days with a washout period of 7 days between dosing periods. Blood samples for pharmacokinetic analysis were taken over the 24 h period following the final dose of omeprazole.

RESULTS

Geometric means and ratios were as follows: C(max) was 555 for omeprazole/alginate and 558 for omeprazole alone (ratio 99.55%, 90% confidence interval 82.75-119.75%; AUC(0-t) was 2050 for omeprazole/alginate and 2094 for omeprazole alone (ratio 97.90%, 90% confidence interval 87.83-109.12%); AUC(0-a) was 2247 for omeprazole/alginate and 2231 for omeprazole alone (ratio 100.74%, 90% confidence interval 90.05-112.70%). Mean values for T(max), K(el) and T(1/2) were also similar for the two treatment regimens.

INTERPRETATION & CONCLUSION

As the 90 per cent confidence intervals for the geometric mean ratios for C(max), AUC(0-t), and AUC(0-alpha) are all contained within the bioequivalence interval of 80-125 per cent, it can be concluded that the administration of this liquid alginate suspension does not affect the pharmacokinetic profile of omeprazole.

Rapid onset of effect of sodium alginate on gastro-oesophageal reflux compared with ranitidine and omeprazole, and relationship between symptoms and reflux episodes

The objective of the open, randomised, four-period crossover study was to compare the time of onset of effect of sodium alginate (SA), omeprazole, ranitidine and control, based on oesophageal and intragastric pH and to determine any correlation between reflux symptoms and episodes in volunteers suffering from occasional gastro-oesophageal reflux. SA showed extensive prevention of acid exposure in the oesophagus compared with other treatments during the first hour. Overall, SA was more effective than control or omeprazole and comparable with ranitidine. There was little evidence of association between 'oesophageal' symptoms and reflux episodes, but associations between 'gastric' symptoms and acidity in the oesophagus, fundus and corpus were apparent. For an immediate reduction in gastro-oesophageal reflux into the oesophagus and gastric acidity during the first hour, SA was significantly superior to control, ranitidine and omeprazole. Ranitidine showed a superior effect from 2 h, consistent with its pharmacological mode of action.

Alginate as a source of dietary fiber

Alginate, an algal polysaccharide, is widely used in the food industry as a stabilizer, or as a thickening or emulsifying agent. As an indigestible polysaccharide, alginate may also be viewed as a source of dietary fiber. Previous work has suggested that dietary fibres may protect against the onset and continuation of a number of cardiovascular and gastrointestinal diseases. This article aims to examine what is currently understood about the fiber-like activities of alginate, particularly its effects on intestinal absorption and the colon, and therefore aims to gauge the potential use of alginate as a dietary supplement for the maintenance of normal health, or the alleviation of certain cardiovascular or gastrointestinal diseases.

Characterisation of adherens and tight junctional molecules in normal animal larynx; determining a suitable model for studying molecular abnormalities in human laryngopharyngeal reflux

BACKGROUND

The disruption of intercellular junctions in the larynx is a pathological feature of laryngopharyngeal reflux (LPR). Good experimental models are necessary to gain greater insight into the molecular mechanisms and alterations that result from abnormal exposure of the laryngeal epithelium to acid refluxate.

AIMS

To characterise laryngeal tissues from different species to determine the most suitable for use in experimental studies of LPR.

METHODS

Human and non-human laryngeal tissues (mouse, rat, guinea pig, porcine, and rabbit) were studied. Histological characterisation was performed by light microscopy. The expression and subcellular localisation of adherens junctional molecules (E-cadherin and beta catenin) was evaluated by immunohistochemistry, and tight junction molecules (occludin and zonula occludens 1 (ZO-1)) by western blotting. The ultrastructural features of porcine and human tissue were assessed by electron microscopy.

RESULTS

Porcine tissue revealed both respiratory-type and stratified squamous epithelium, as seen in the human larynx. The expression and subcellular localisation of the E-cadherin-catenin complex was detected in all species except mouse and rat. The pattern of ZO-1 and occludin expression was preserved in all species.

CONCLUSION

The expression of intercellular junctional complexes in porcine epithelium is similar to that seen in humans. These results confirm the suitability of these species to study molecular mechanisms of LPR in an experimental system.

Straining at stool and stool frequency in free-living and institutionalised older adults

BACKGROUND

The diagnosis of functional constipation according to Rome II criteria includes assessment of straining. However the prevalence in older adults is unknown.

AIMS

To assess the prevalence of straining and its association with stool frequency in free-living (FL) and institutionalised (INS) older adults.

METHODS

50 FL subjects (mean age 74 years, range (65-97), 42% male) and 42 INS subjects (mean age 84 years, range (69-101) 36% male) were recruited. Stool frequency and straining to start and to finish were prospectively recorded by subjects for 7 consecutive days in a bowel habit diary. Statistical analyses were performed using the Chi-square or the Pearson correlation coefficient as appropriate.

RESULTS

The mean stool frequency (n/week) was significantly higher (p <0.001) in the FL group compared with the INS group (11.7 and 4.9 respectively). The percentage of subjects experiencing straining to start on more than 25% of occasions was significantly lower in the FL compared with the INS group (34% and 64% respectively, chi2 = 8.4, p = 0.004, df = 1). The percentage of subjects experiencing straining to finish on more than 25% of occasions was significantly lower in the FL compared with the INS group (16% and 41% respectively, chi2 = 6.9, p = 0.009, df = 1).

CONCLUSIONS

FL subjects had significantly higher stool frequency and had to strain passing a stool (to start and to finish) less often than their INS counterparts. Moreover, straining to start was experienced more often than straining to finish in both groups.

Alginate rafts and their characterisation

Alginate/antacid anti-reflux preparations are designed to provide symptom relief by forming a physical barrier on top of the stomach contents in the form of a neutral floating gel or raft. This study tested the in vitro effectiveness of a range of liquid products in forming rafts that were cohesive, buoyant, voluminous, resistant to reflux and durable under conditions of movement (resilient). The products tested had a wide range of acid neutralising capacities (ANCs). It was found that products with a high ANC and no calcium ion source formed rafts of low strength, weight and volume, which appeared more as floating precipitates than coherent gels. Products with a high ANC and a calcium ion source formed medium strength, weight and volume rafts. Products with a low ANC formed strong coherent rafts with medium to large weight and volume, and those with low ANC and a calcium ion source formed the strongest rafts. Products with stronger rafts were found to be more resilient and more resistant to reflux in an in vitro reflux model. Significant overall differences in raft buoyancy were found between products forming coherent rafts but these could not be related to the product formulation or amount of available carbon dioxide.

Laxative use and its relationship with straining in a London elderly population: free-living versus institutionalised

BACKGROUND

The diagnosis of functional constipation according to Rome II criteria includes assessment of straining. However the prevalence in older adults is unknown. Moreover, laxative use increases with age, especially in the elderly.

AIMS

to assess the prevalence of straining and its association with laxative use in free-living (FL) and institutionalised (INS) older adults.

METHODS

50 FL (mean age 74 years, 42% male) and 42 INS subjects (mean age 84 years, 36% male) were recruited. Straining to start and to finish defecation were prospectively recorded by subjects for 7 consecutive days in a bowel habit diary. Concurrently, the subjects recorded any laxative use during the 7 days study. Statistical analyses were performed using the Chi-square statistic.

RESULTS

20% of FL and 65% of INS subjects recorded taking laxatives during the study week. Of the 40 FL subjects not taking laxatives, 30 had to strain to start on 25% or less of occasions and 36 had to strain to finish on 25% or less of occasions (chi(2) = 7.2; p = 0.012 and chi(2) = 5.4; p = 0.041, respectively). In the INS group, although 64% of subjects taking laxatives had to strain on more than 25% of occasions, the Chi-square test was not statistically significant.

CONCLUSIONS

From our results, it seems that laxatives were used appropriately in the FL, with the majority of those taking laxatives having to strain to start on more than 25% of occasions.

Use of the 'ex vivo' test to study long-term bacterial survival on human skin and their sensitivity to antisepsis

AIMS

To determine bacterial survival on human skin and their sensitivity to antisepsis.

METHODS AND RESULTS

An 'ex vivo' protocol which uses human skin samples placed into diffusion cells, and electron microscopy (EM), were used to study the growth of Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa inoculated onto skin samples over a 46-h incubation period at 32 degrees C. Concurrently variation in skin pH was evaluated at different time intervals during this period. In addition the antimicrobial activity of three antiseptics against the incubated micro-organisms was assessed quantitatively with the 'ex vivo' test, while their detrimental effects against bacteria were observed by EM. All three bacteria were still present in high number after 46 h inoculation on skin, although the concentration of E. coli and S. aureus were reduced by 2.74 and 1.58 log(10) reduction, respectively, over this period of time. Electron micrographs showed clear evidence of cell division and some bacteria appeared to be embedded into the skin layers. The antiseptics tested had some antibacterial activity against bacteria incubated on skin for 3 and 10 h, and EM evidence showed some morphological damages including cellular blebbing and the presence of fibrillar material around the cells. All micro-organisms had an acidifying effect on skin samples.

CONCLUSIONS

Here, it was shown that bacterial pathogens can survive and grow when incubated on human skin. In addition, it is possible that they can penetrate the stratum corneum, which can provide some protection against antisepsis.

SIGNIFICANCE AND IMPACT OF THE STUDY

The apparent low bactericidal activity of biocides attributed in part to bacterial protection from skin layers is particularly important to assess in order to ensure antisepsis efficacy.

Comparison of two in vivo and two ex vivo tests to assess the antibacterial activity of several antiseptics

An ex vivo test was adapted to mimic the in vivo conditions of testing antiseptic activity on human forearms and in the European Standard Hygienic Handwash Test (BSEN 1499). The study was to validate the ex vivo protocols using 4.8% (w/v) para-chloro-meta-xylenol (PCMX, neat Dettol), 0.5% (w/v) triclosan in 70% (v/v) isopropanol, and 2% (v/v) povidone-iodine against a high bacterial inoculum (>10(8) cfu/mL) of Escherichia coli NCTC 10538. Two ex vivo tests using human skin samples, including one introducing a mechanical rubbing effect, were compared with two corresponding in vivo tests (the forearm test and the BSEN handwashing test). All antiseptics assessed in vivo (forearm and handwash tests) produced reductions in bacterial counts that were significantly greater than those for the non-medicated soft soap control. When assessed ex vivo without rubbing, only PCMX and povidone-iodine achieved reductions significantly greater than soft soap. When assessed ex vivo with mechanical rubbing, only PCMX and triclosan achieved reductions significantly greater than soft soap. Overall, the antiseptics at the concentrations tested were more active when tested in vivo than ex vivo. The addition of a mechanical effect, either in vivo by the volunteers washing their hands or ex vivo by a drill rubbing two skin samples against each other, produced a significantly greater reduction in bacterial concentrations. The ex vivo tests were easily adapted to mimic in vivo protocols. The value of such tests, particularly the one that includes a rubbing effect, may be significant as they avoid the need for human volunteers.

Feasibility of a bioadhesive drug delivery system targeted to oesophageal tissue

This contribution examines the feasibility of utilising an oesophageal-adhesive alginate layer to support model drug particles. Such a bioadhesive system offers the prospect of local drug delivery to the oesophagus, which in turn has applications in the treatment of conditions including gastro-oesophageal reflux disease and oesophageal cancer. Surface-modified (amine, carboxylate and sulfate) as well as neutral fluorescent beads were investigated as model drug particles. A fluorescence assay technique was utilised to quantify the extent and duration of adhesion of a fixed dose of these particles to excised porcine oesophageal tissue. Retention of the particles was investigated both from aqueous systems and within an adhesive alginate solution. After 30 min significantly higher adhesion of neutral beads was recorded from the alginate solution as compared to the aqueous suspension (n = 6, P < 0.05). The beads that possessed a negative charge showed significantly greater retention within the alginate carrier (n = 6, P < 0.05). However, the amine-modified beads showed retention profiles that were similar both within the alginate carrier and within the aqueous suspension (n = 6, P > 0.05).

A simple, high throughput method for the quantification of sodium alginates on oesophageal mucosa

Sodium alginate is a potential bioadhesive, but the lack of a convenient and suitable method for its quantification on the mucosal surface complicates the evaluation of its mucosal retentive properties. This paper develops and evaluates a spectrophotometric method for the rapid quantification of a range of sodium alginates differing in chemical composition, and investigates how quantification was influenced by the presence of oesophageal mucosa. The method, based on dye complexation with 1,9-dimethyl methylene blue (DMMB) was sensitive to alginate molecular weight and uronic acid composition, however, no significant correlations between assay performance and alginate molecular characteristics were demonstrated. The assay was also influenced by complexation time, calcium ions and mucin, but was unaffected by the presence of oesophageal tissue scrapings. The assay proved to be capable of quantifying sodium alginate with excellent linearity (r = 0.999), reproducibility (CV < 3%) and sensitivity (0.3 g l(-1)) and proved to be a precise, high-throughput method that may be used for quantifying the retention of sodium alginate on oesophageal mucosa.

Assessment of skin viability: is it necessary to use different methodologies?

BACKGROUND/AIM

Skin is complex and may display variable structural and metabolic change 'ex vivo'. The present study aimed to follow measures of skin viability and evaluate their usefulness as markers of viability.

MATERIALS AND METHODS

We evaluated the viability of skin samples fresh or after being frozen and subsequently thawed. Assessments included histopathological appearance, lactate dehydrogenase (LDH) activity, oxygen consumption and skin pH.

RESULTS

Morphological investigations of fresh and frozen skin samples using light and electron microscopy showed samples with relatively well-defined epidermis and dermis. Frozen samples showed some sign of stratum corneum fragmentation, although this was not obvious. LDH activity measured in fresh samples kept at 4 degrees C was low, but it was stable up to 7 days. Fresh samples kept at 32 degrees C had a comparable LDH activity to the ones kept in the fridge up to 4 days. Frozen samples, thawed and then kept at 4 degrees C showed a stable LDH activity after 24 h of incubation. However, frozen samples incubated at 32 degrees C demonstrated a high variability in results, with up to 800 U/L of LDH activity after 5 days of incubation. Freshly excised as well as freshly thawed samples showed the highest respiration rates. Fresh and thawed samples stored for a long period of time had a significantly lower (sometimes non-existent) oxygen consumption rate. Our results also showed an increase in the oxygen consumption rate of fresh samples being incubated at 32 degrees C for 24 h. The oxygen consumption rate for all samples reached a plateau within the 15-min measurement period and even the fresh samples did not deplete all the oxygen from the medium. Skin samples ex vivo showed a significantly higher pH than human skin in vivo, and when incubated for 46 h at 32 degrees C, fresh samples had a significantly lower pH than frozen samples. All protocols were reproducible and freshly excised and freshly thawed skin samples showed the highest rates of viability.

CONCLUSION

ex vivo skin shows variation of several parameters over time. It is recommended to use two or three techniques for evaluation of skin viability including at least oxygen measurement and an enzyme assay.

Chloroxylenol- and triclosan-tolerant bacteria from industrial sources

Potential development of bacterial tolerance to biocides in the industrial environment is examined in this study. Bacteria tolerant to the phenolic-type agent para-chloro-meta-xylenol (PCMX) and the bis-phenol 2,4,4'-trichloro-2'-hydroxydiphenylether (triclosan) were isolated from industrial sources and identified. Minimum inhibitory concentrations (MICs) were determined and compared with those of culture collection (standard) strains. Of around 100 isolates originally obtained, most were naturally tolerant species such as Pseudomonas spp., or showed low tolerance levels. PCMX-tolerant isolates of Pseudomonas stutzeri and triclosan-tolerant isolates of Citrobacter freundii and Acinetobacter johnsonii were retained for further study. Of these, only P. stutzeri and A. johnsonii showed elevated tolerance compared with the standard strains. There was no evidence of tolerance to the other biocide except for Pseudomonas aeruginosa (an intrinsically tolerant microorganism), and tolerances were stable in the absence of selective pressure except for A. johnsonii. Attempts to select or generate increased tolerance in the standard strains were unsuccessful. High tolerances in terms of MIC were not reflected in terms of lethal effects. This study did not produce any evidence suggesting that the presence of residual biocide concentrations in the industrial environment promotes the emergence of bacterial tolerance for them.

Energy intakes of institutionalised and free-living older people

Inadequate energy intake is common in older adults, especially in those living in institutions. Underweight in older people is associated with increased risk of morbidity and mortality. The objective of this study was to compare energy and percentage of total energy from protein, fat, carbohydrate and alcohol between institutionalised (INS) and free-living (FL) older people. 16 INS volunteers (mean age 88 years, 20% male) and 23 FL volunteers (mean age 75 years, 48% male) were recruited. Food intake was measured using the 4-day weighed inventory method. Nutritional analysis was carried out using the computer program Dietplan5 for Windows. Energy intakes were significantly lower in the INS group compared with the FL group, due to the lower amount of food eaten. The energy intakes in the INS group were below the Estimated Average daily Requirement (1). The energy derived from fat was higher and the energy derived from carbohydrate lower than dietary recommendations in the INS group.

An in vitro mucosal model for prediction of the bioadhesion of alginate solutions to the oesophagus

This paper discusses the development of an in vitro model utilised to assess the adhesion of alginate solutions to porcine oesophageal tissue. The methodology involved the construction of retention apparatus onto which sections of tissue were mounted. Fluorescently labelled alginate solutions of known rheological profile were dispensed onto the tissue at a concentration of 2% w/v. A washing solution was applied at a specified rate to mimic saliva flow and the eluted material collected. Fluorimetric analysis allowed dose retention to be assessed as a function of time. The effect of the nature of the washing solution and the choice of alginate were investigated. It was found that after 30 min up to 20% of the applied alginate dose remained associated with the tissue, regardless of the alginate selected from the range examined. The nature of the washing medium did not have a significant effect on retention, irrespective of the inherent mucin concentration. Overall this study indicated that the technique presented offers a viable means of studying bioadhesion of liquids and also demonstrates that alginate solutions may have an application as bioadhesive agents for localisation within the oesophagus.

Cell biology of laryngeal epithelial defenses in health and disease: preliminary studies

Esophageal epithelium has intrinsic antireflux defenses, including carbonic anhydrases (CAs I to IV) that appear to be protective against gastric reflux. This study aimed to investigate the expression and distribution of CA isoenzymes in laryngeal epithelium. Laryngeal biopsy specimens collected from the vocal fold and interarytenoid regions were analyzed by Western blotting and immunofluorescence. Carbonic anhydrases I and II were expressed by the majority of samples analyzed. In contrast, CA III was differentially expressed in the interarytenoid samples and was not detected in any vocal fold samples. The expression of CA III was increased in esophagitis as compared to normal esophageal tissue. Carbonic anhydrase I and III isoenzymes were distributed cytoplasmically in the basal and lower prickle cell layers. The laryngeal epithelium expresses some CA isoenzymes and has the potential to protect itself against laryngopharyngeal reflux. Laryngeal tissue may be more sensitive to injury due to reflux damage than the esophageal mucosa because of different responses of CA isoenzymes.

The effect of chitin and chitosan on the proliferation of human skin fibroblasts and keratinocytes in vitro

The effects of chitin [(1 --> 4)-2-acetamido-2-deoxy-beta-D-glucan] and its partially deacetylated derivatives, chitosans, on the proliferation of human dermal fibroblasts and keratinocytes were examined in vitro. Chitosans with relatively high degrees of deacetylation strongly stimulated fibroblast proliferation while samples with lower levels of deacetylation showed less activity. Fraction, CL313A, a shorter chain length, 89% deacetylated chitosan chloride was further evaluated using cultures of fibroblasts derived from a range of human donors. Some fibroblast cultures produced a positive mitogenic response to CL313A treatment with proliferation rates being increased by approximately 50% over the control level at an initial concentration of 50 microg/ml, whilst others showed no stimulation of proliferation or even a slight inhibition (< 10%). The stimulatory effect on fibroblast proliferation required the presence of serum in the culture medium suggesting that the chitosan may be interacting with growth factors present in the serum and potentiating their effect. In contrast to the stimulatory effects on fibroblasts, fraction CL313A inhibited human keratinocyte mitogenesis with up to 40% inhibition of proliferation being observed at 50 microg/ml. In general highly deacetylated chitosans were more active than those with a lower degree of deacetylation. These data demonstrate that highly deacetylated chitosans can modulate human skin cell mitogenesis in vitro. Analysis of their effects on cells in culture may be useful as a screen for their potential activity in vivo as wound healing agents, although in the case of fibroblasts it is important to select appropriate strains of cells for use in the screen.

Esophageal mucin: an adherent mucus gel barrier is absent in the normal esophagus but present in columnar-lined Barrett's esophagus

OBJECTIVES

The presence of a protective adherent mucus gel barrier against gastric reflux in the healthy esophagus is uncertain. The aim was to characterize the surface mucin composition and determine the extent of any adherent mucus gel layer on the normal esophagus, and compare this with that in Barrett's esophagus.

METHODS

Isolated surface mucins were characterized by density centrifugation, gel filtration chromatography, and chemical composition. Adherent surface mucus was visualized in situ on unfixed and cryostat sections of mucosa and biopsies using a method that preserves mucus layer thickness.

RESULTS

There was a complete absence of adherent mucus gel layers on normal human, pig, and rat esophagi. This was in contrast to the thick adherent mucous layer (median thickness = 100-200 microm) seen on the corresponding gastric mucosa. Small quantities of glycoprotein with a composition characteristic of a secretory mucin were isolated from the pig esophagus surface. The mucin, density range between 1.44 and 1.48 g x ml(-1), contained 80% carbohydrate and was rich in serine, threonine, and proline. The mucin fragmented into smaller glycoprotein units on proteolysis and partially on reduction. Cryostat sections from columnar-lined esophageal biopsies had a substantial adherent surface mucous layer (median thickness = 90 microm, interquartile range = 84-94 microm) staining for neutral mucins (gastric-type epithelium) and acidic mucins (intestinal metaplasia).

CONCLUSIONS

A secretory mucin, with an analysis distinct from that of gastric or salivary mucin, is present in very small quantities on the esophageal mucosa and in amounts insufficient to form an adherent gel layer. It is unlikely that mucus has a role in protecting the normal esophagus against reflux. However, an adherent mucous layer was observed over columnar-lined esophagus, and this may protect against reflux.

The gastrointestinal transit profile of 14C-labelled poly(acrylic acids): an in vivo study

The gastrointestinal distribution profiles for three 14C-labelled poly(acrylic acid)s of different average molecular weights and degrees of cross-linking have been established using the rat model. Despite initial differences in transit times and retention characteristics, these structural features were found to be of little influence to the overall gastrointestinal transit of the materials under consideration. No evidence for the systemic absorption of any of the polymers could be identified.

Synthesis of radiolabeled congeners of the carbomers: (14)C-labeled poly(acrylic acid)s

A general method for the synthesis of (14)C-acrylic acid is described in detail. The material is used for the synthesis of a range of radiolabeled poly(acrylic acid)s in which the (14)C-label forms an integral part of the polymer backbone. The chemical structure of the synthesized polymers is examined in the light of spectroscopic data, molecular weight determinations, and rheological studies.

An investigation of mucus/polymer rheological synergism using synthesised and characterised poly(acrylic acid)s

A range of poly(acrylic acid)s with different average degrees of polymerisation and cross-linking densities were synthesised using a solution polymerisation process. The rheological characteristics of aqueous dispersions of these materials and those of mixtures with homogenised pigs gastric mucus were investigated using dynamic oscillatory rheology, and compared to the known mucoadhesive Carbopol 934P. From the storage moduli, the rheological synergy and relative rheological synergy were calculated, and the effects of concentration and pH on this considered. Generally, the larger the molecular weight (and degree of cross-linking), the greater the rheological synergy, with Carbopol 934P giving the most pronounced effect. Rheological synergy was seen to be concentration-dependent, and a maximum concentration to produce an optimum effect was evident. Acid pHs were seen to favour synergy, although in marked contrast to previous literature reports, the optimum mucus-polymer interaction was not observed at the half ionised value (pH = pKa) but at pH regimes that were unique to each polymer type. This could be influenced by the structural constrains imposed on potential hydrogen bonded interactions. It was concluded that synthesising poly(acrylic acid)s with better defined physicochemical properties than commercially available polymers will advance the study of the phenomenon of rheological synergy.

A novel application of NMR microscopy: measurement of water diffusion inside bioadhesive bonds

The self-diffusion coefficient of water (D) inside bioadhesive bonds formed by dry and prehydrated hydrophilic matrices has been spatially resolved using nuclear magnetic resonance (NMR) microscopy. One-dimensional profiles showing the variation of D inside bioadhesive bonds were calculated from nine diffusion-weighted profiles obtained immediately after bond formation and every 5 min for 30 min. The resulting data indicated that the hydration state of a hydrophilic matrix can significantly and dramatically influence the dynamics of water movement inside a bioadhesive bond.

Determination of the antibacterial efficacy of several antiseptics tested on skin by an 'ex-vivo' test

There are many skin antiseptics commercially available. Although their antibacterial activity has often been well studied, their potential effectiveness on skin remains poorly documented. To date, in-vivo protocols designed for the testing of the antimicrobial efficacy of antiseptics cannot use, for ethical reasons, pathogenic bacteria or new formulations whose toxicity in human subjects is unknown. An 'ex-vivo' test was recently developed to overcome these problems. Freshly excised human skin from abdominal or breast reduction was placed in a diffusion cell containing a maintenance medium in the recipient compartment. A bacterial inoculum was then applied to the stratum corneum and, after a drying step, antiseptic formulations were evaluated for their antimicrobial activity. Several micro-organisms were investigated: - Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), Enterococcus faecalis, vancomycin-resistant Ent. faecium (VRE), S. epidermidis, Pseudomonas aeruginosa and Escherichia coli--with several biocides--para-chloro-meta-xylenol (PCMX, active compound of Dettol), povidone iodine, triclosan (in isopropanol) and chlorhexidine. Results from the ex-vivo test were compared with results obtained in suspension and glass-carrier tests. The bactericidal activity of the biocides depended upon the test performed and results were generally significantly different from one method to the other. All biocides tested in the suspension test achieved >4 log10 reduction in viable bacterial concentrations, apart from povidone iodine tested against Ent. faecalis and VRE. The antibacterial activity of biocides tested in the glass-carrier test was significantly lower than in the suspension test, with the exception of triclosan in isopropanol, which was as effective in both suspension and glass-carrier test. In the ex-vivo test, triclosan in isopropanol achieved a log10 reduction in viable bacterial concentration of 1.105-1.771 (with the exception of P. aeruginosa with 0.758 log10 reduction). PCMX, povidone iodine and chlorhexidine achieved log10 reductions in viable bacterial concentration of 0.303-0.901. Chlorhexidine tested against P. aeruginosa produced a 1.94 log10 reduction in concentration. These results confirm previous observations about the need for testing the antimicrobial activity of antiseptics on skin surface to determine their in-situ efficacy and encourage further the use of the ex-vivo protocol.

Dietary fibre, physicochemical properties and their relationship to health

Dietary carbohydrates that escape digestion and absorption in the small intestine include non-digestible oligosaccharides (carbohydrates with a degree of polymerisation between three and ten), resistant starch and non-starch polysaccharides. The physiological effects of this heterogeneous mixture of substrates are partly predictable on the basis of their physicochemical properties. Monosaccharide composition and chain conformation influence the rate and extent of fermentation. Water-holding capacity affects stool weight and intestinal transit time. Viscous polysaccharides can cause delayed gastric emptying and slower transit through the small bowel, resulting in the reduced rate of nutrient absorption. Polysaccharides with large hydrophobic surface areas have potentially important roles in the binding of bile acids, carcinogens and mutagens. Ispaghula is capable of binding bile acids through a large number of weak binding sites on the polysaccharide structure, and having greatest effect on the potentially more harmful secondary bile acids deoxycholic acid and lithocholic acid.

Effect of ispaghula husk on the faecal output of bile acids in healthy volunteers

Faecal bile acids are associated with both colorectal cancer and serum cholesterol levels. We investigate whether dosing with ispaghula husk affects the faecal bile acid weights and concentrations in healthy adults. Sixteen healthy volunteers consumed 7.0 g/day ispaghula husk, containing 5.88 g/day Englyst-determinable dietary fibre, for the middle 8 weeks of a 12-week period. Stool samples were collected, analysed for faecal bile acids and their form and dry weight determined. Correlations between the faecal bile acids, the stool parameters and the dietary intake were tested. Ispaghula husk treatment significantly lowers faecal lithocholic and isolithocholic acids and the weighted ratio of lithocholic acids to deoxycholic acid. These effects revert towards their initial states at the end of the treatment period. These changes in the faecal bile acid profiles indicate a reduction in the hydrophobicity of the bile acids in the enterohepatic circulation.

The influence of ispaghula husk on bowel habit

Frequency of defaecation, faecal form, straining at the start and end of defaecation, feelings of incomplete evacuation of faeces and urgency of defaecation were recorded in 69 healthy volunteers during three distinct 28-day study phases: pre-treatment, treatment with ispaghula husk and post-treatment. During treatment there was a significant increase (P < 0.001) in stool frequency and significant decreases in straining at the start (P < 0.001) and end (P < 0.001) of defaecation and in feelings of incomplete evacuation (P < 0.001). There was evidence of a beneficial residual effect after treatment had stopped. There are indications that ispaghula husk (Fybogel Orange) is of benefit in relieving constipation symptoms in apparently healthy people.

A multi-centre, general practice comparison of ispaghula husk with lactulose and other laxatives in the treatment of simple constipation

An open, multi-centre study in general practice compared with efficacy, speed of action and acceptability of ispaghula husk (Fybogel Orange, Reckitt & Colman Products, UK), lactulose and other laxatives in the treatment of patients with simple constipation. A total of 65 GPs recruited 394 patients, of whom 224 (56.9%) were assigned to treatment with ispaghula and 170 (43.1%) to other laxatives (mainly lactulose) for up to four weeks. Thirteen patients withdrew before treatment started, so that 381 entered the study. Patients were assessed by their GP before entry and after two and four weeks of treatment. Patients also kept daily records of their bowel movements. After four weeks' treatment, ispaghula husk was assessed by the GPs to be superior to the other treatments in improving bowel function and in overall effectiveness, palatability and acceptability. Patients' reports of time to first bowel movement showed little difference between the treatments. Over 60% of patients in each treatment group passed a first motion within 24 hours, and over 80% within 36 hours. Ispaghula husk produced a higher percentage of normal, well-formed stools and fewer hard stools than other laxatives. Incidences of soiling, diarrhoea and abdominal pain were lower in the group receiving ispaghula husk. Overall, ispaghula husk was an effective treatment for simple constipation, and was associated with better stool consistency and a lower incidence of adverse events compared with lactulose or with other laxatives.

Mucus and H. pylori

A continuous, adherent mucus gel layer with mucosal bicarbonate secretion is the initial protective barrier in the stomach and duodenum against erosion by the gastric juice. H. pylori resides within the adherent mucus gel layer close to the epithelial surface. The barrier function of the mucus layer in vivo depends on (i) its thickness, and (ii) its gel structure, a property which is linearly dependent on the polymeric mucin content. We have shown in vivo that H. pylori colonisation alone did not decrease the thickness of the adherent gastric mucus barrier, although there was a mean 20% decrease in mucus thickness in those H. pylori positive subjects with underlying gastric atrophy. There was, however, a significant mean 18% reduction in the gel-forming polymeric mucin content of mucus from H. pylori subjects, independent of underlying atrophy. Studies in vitro suggest this loss of gel structure might arise from a H. pylori mediated, high local pH generated by urease activity rather than by proteolysis. This study shows that H. pylori infection alone does not compromise the overall integrity of the mucus barrier in vivo. However, in the immediate environment of the organism there appears to be a localised loss of mucus gel structure. The mucus barrier is compromised if H. pylori associated gastric atrophy or peptic ulceration follows.

Interaction of polyacrylates with porcine pepsin and the gastric mucus barrier: a mechanism for mucosal protection

1. The mechanism of interaction of the polyacrylates, carbopols with the mucus barrier in vivo has been investigated in vitro. 2. Carbopol caused a dramatic increase in the viscosity of porcine gastric mucin solutions that was up to 19-fold greater than that of the sum of the individual polymers. 3. The mucin-carbopol interaction was stable after an initial 30 min period for up to 36 h at 25 degrees C or 37 degrees C. It was reduced by increasing the temperature from 20 degrees C to 45 degrees C, was unaffected by pH and ionic strength, but was enhanced by Ca2+. 4. The magnitude of the interaction between mucin and carbopol depended on the polymeric structure of the mucin and the molecular size and level of cross-linking of the carbopol. 5. The interactions were reversible and increased with increasing carbopol and mucin concentration. The dramatic increase in viscosity can be explained in terms of space filling by the mucin molecules leading to predominantly carbopol-carbopol interactions. 6. Carbopol 934P inhibits pepsin hydrolysis and therefore has potential as a mucosal protective agent in vivo.

The gastroduodenal mucus barrier and its role in protection against luminal pepsins: the effect of 16,16 dimethyl prostaglandin E2, carbopol-polyacrylate, sucralfate and bismuth subsalicylate

Mucus and bicarbonate secretions have been widely implicated as an important pre-epithelial protective barrier against autodigestion of the gastric mucosa by acid and pepsin. Evidence from several independent studies shows there is a continuous layer of resilient viscoelastic mucus gel adherent to the surface of the gastroduodenal mucosa. The median thickness of the adherent gastric mucus layer in humans is 180 microns, range 50-450 microns. The epithelial bicarbonate secretion permeates the unstirred matrix of mucus gel neutralizing luminal acid and establishing a pH gradient within the gel. In the duodenum, evidence supports the mucus bicarbonate barrier as a major protective mechanism against acid aggression. The adherent mucus gel, by acting as an effective 'permeability' barrier to pepsin, protects the underlying sensitive mucosa from digestion. However, pepsin slowly digests mucus gel at its luminal surface to produce soluble degraded mucin. In a rat gastric damage model in vivo, pepsin in excess digests the gastric mucus barrier sufficiently rapidly to outweigh new mucus secretion and lead to breaching of the mucus barrier with the formation of small punctate ulcers in the epithelium accompanied by mucosal haemorrhage. The mucus secretagogue 16,16 dimethyl prostaglandin E2 and the muco-adhesive carbopol-polyacrylate both fully protected the mucosa against pepsin damage by enhancing the protective properties of the mucus barrier. Sucralfate and bismuth subsalicylate were partially effective in protection against pepsin damage but this protection was mainly mediated at the level of the mucosa. In peptic ulcer disease, there is increased mucolytic (mucus degrading) activity in gastric juice and this is associated with an impaired mucin polymeric structure and a weaker mucus barrier.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of fenclofenac on the regeneration of lymphocytes in rats following total body irradiation

The effect of fenclofenac on the regeneration of white blood cells in Sprague-Dawley rats following total body irradiation was investigated. The lowest dose of total body irradiation that would suppress the peripheral blood lymphocyte count by at least 50% was found to be 1.0 Gray in a preliminary experiment. Fenclofenac in a dose of 150 mg/kg/day retarded the regeneration of lymphocytes following total body irradiation of 1 Gray: this effect was also seen in the CD4, CD8 and B-lymphocyte subsets. This suppressive effect in vivo may be due to interference with replicative growth of white blood cells since previous in vitro experiments have shown suppression of lymphocyte growth at a stage later than activation in the cell cycle. The suppressive effects on leucocyte regeneration in vivo suggest that fenclofenac may have promise as an immunosuppressive drug with fewer serious side effects than the currently available immunosuppressive drugs.

Pre- and post-junctional alpha-adrenoceptor-mediated responses in the rat gastric fundus in-vitro

The effects of alpha 1- and alpha 2-adrenoceptor agonists on smooth muscle tone and on cholinergic excitatory and non-adrenergic, non-cholinergic inhibitory responses to field stimulation have been investigated in the rat gastric fundus in-vitro. None of the alpha-adrenoceptor agonists tested, noradrenaline, phenylephrine, cirazoline, guanoxabenz or UK-14,304 showed any contractile effects at concentrations up to 30 microM. In preparations where tone was raised by barium (0.5-2 mM), the mixed alpha 1- and alpha 2-adrenoceptor agonist noradrenaline (0.01-10 microM), and the selective alpha 1-adrenoceptor agonists cirazoline (0.01-10 microM) and phenylephrine (0.01-10 microM) produced concentration-dependent relaxations which were antagonized by the alpha 1-adrenoceptor antagonist prazosin (0.01-1.0 microM). The selective alpha 2-adrenoceptor agonists UK-14,304 (0.03-30 microM) and guanoxabenz (0.03-30 microM), had no relaxant effects in raised tone. UK-14,304 (0.03-1.0 microM) produced a concentration-dependent inhibition of cholinergic nerve-induced responses which was antagonized by the alpha 2-adrenoceptor antagonist idazoxan (0.03-1.0 microM) but not by prazosin (0.03-1.0 microM). Noradrenaline (0.03-1.0 microM) also produced an inhibition of cholinergic nerve-induced responses which was antagonized by idazoxan (0.03-1.0 microM). A small component of the noradrenaline inhibitory effects was antagonized by prazosin (10%). Cirazoline (0.03-1.0 microM) produced a small inhibition of cholinergic nerve-induced responses which was antagonized by prazosin (0.03-1.0 microM). The prazosin-sensitive components of the inhibitory effects of noradrenaline and cirazoline occurred at concentrations which also produced post-junctional relaxation.(ABSTRACT TRUNCATED AT 250 WORDS)

Alpha 2-adrenoceptor antisecretory responses in the rat jejunum

1. Addition of noradrenaline (5 microM), UK-14,304 (0.1 microM) or phenylephrine (100 microM) to the serosal surface of sheets of rat jejunum mounted in Ussing type chambers decreased resting transepithelial short circuit current (SSC). These responses were inhibited by the selective alpha 2-adrenoceptor antagonist idazoxan (0.5-5.0 microM) but were not significantly affected by the alpha 1-adrenoceptor antagonist corynanthine (100 microM). 2. All three agonists caused a dose-related reduction of SSC which had been elevated by prior addition of theophylline (4 mM). UK-14,304 was 8.1 times more potent than noradrenaline and 76.2 times more potent than phenylephrine. Idazoxan (10 nM-1 microM) caused rightward, parallel displacements of the concentration-response curves for noradrenaline and UK-14,304; PA2 values were 7.87 and 8.02 respectively. Dose-response curves to noradrenaline were unaffected by prazosin (1 microM). 3. The reduction by noradrenaline (10 microM) of SCC which had been elevated by theophylline (4 mM) was not significantly affected by tetrodotoxin (5 microM), suggesting that noradrenaline reduces SCC in rat jejunum via a direct mucosal mechanism. 4. The resting SCC was markedly reduced in chloride-free PSS and under these conditions, noradrenaline did not elicit any further fall in SCC. In bicarbonate-free physiological salt solution (PSS) the resting SCC and the noradrenaline-induced fall in SCC were not significantly different from those in normal PSS. It is concluded that the decrease in SCC observed with noradrenaline, UK-14,304 and phenylephrine is mediated via stimulation of postjunctional alpha 2-adrenoceptors.

The effect of alpha 2-adrenoceptor agonists on the acid secretory responses of rat isolated gastric mucosa to electrical field stimulation

The effects of clonidine, UK-14,304, noradrenaline, para-aminoclonidine and phenylephrine were examined on the acid secretory response of the rat isolated gastric mucosa preparation to electrical field stimulation. Clonidine, UK-14,304, noradrenaline and para-aminoclonidine but not phenylephrine (10 microM) reduced the response of the gastric mucosa stimulated at 2.5 Hz; gastric mucosae stimulated at higher frequencies were insensitive to the action of these alpha 2-adrenoceptor agonists. The inhibitory effect of the selective alpha 2-adrenoceptor agonist UK-14,304 was antagonized by idazoxan but not by prazosin. These findings indicate that clonidine and other alpha 2-adrenoceptor agents inhibit the acid secretory response of the rat gastric mucosa to electrical field stimulation by an action at alpha 2-adrenoceptors, which are probably located on cholinergic nerve terminals.

Effects of idazoxan on catecholamine systems in rat brain

Experiments have been performed to assess the potency of idazoxan (RX 781094) at alpha and beta-adrenoceptors and dopamine receptors and on catecholamine uptake processes in rat brain. The effects of idazoxan on the turnover rates of noradrenaline and dopamine have been determined. Radioligand binding studies with cerebral cortex membranes have demonstrated that idazoxan exhibits 46-fold selectivity for alpha 2-adrenoceptors labelled by (3H)-idazoxan (Mean Ki +/- S.E.M. = 3.1 +/- 0.4 nM) compared with alpha 1-adrenoceptors labelled by (3H)-prazosin (Mean Ki +/- S.E.M. = 142 +/- 27 nM). Under the same conditions, yohimbine showed 6-fold selectivity for alpha 2-adrenoceptors. Idazoxan had low affinity for beta-adrenoceptors labelled by (3H)-dihydroalprenolol (IC50 value greater than 10 microM), for dopamine receptors labelled by (3H)-domperidone (IC50 value greater than 20 microM), for the (3H)-noradrenaline uptake site in rat hypothalamus (IC50 = 31 microM) and for the (3H)-dopamine uptake site in rat striatum (IC50 value approximately 800 microM). In rats treated with alpha-methyl-p-tyrosine, idazoxan (10-80 mg/kg, po) produced a marked increase (63% at 10, 217% at 20 mg/kg, po) in the apparent rate of turnover of noradrenaline in rat cortex/striatum, without affecting the rate of turnover of dopamine. This was in contrast to yohimbine (5-20 mg/kg, po) which increased the turnover rates of both catecholamines. In the absence of alpha-methyl-p-tyrosine, idazoxan (5-40 mg/kg, po) produced a dose related increase in the MHPG concentration and a small (20-30%) reduction in the steady state concentration of NA; the duration of the reduction was dose-related. DA steady state concentrations were unaffected. Idazoxan is a new selective alpha 2-adrenoceptor antagonist which should prove a valuable investigative tool in neurochemical studies and which may be a useful clinical agent in the management of the affective disorders.

Analeptic effects of centrally injected TRH and analogues of TRH in the pentobarbitone-anaesthetized rat

The effect of intracerebral injection of TRH and several biologically stable TRH analogues in the pentobarbitone anaesthetized rat was examined. Bilateral injection of TRH (5.0 micrograms total dose) and the analogues RX 77368 (0.01-1.0 microgram), CG 3509 (0.1-1.0 microgram), DN-1417 (1.0 microgram) and MK-771 (1.0 microgram) into the nucleus accumbens reduced the pentobarbitone-induced sleeping time. The TRH metabolite DKP (5 micrograms) had no effect on the sleeping time following intra-accumbens injection. Intra-septal injection of TRH (1.0-5.0 micrograms), RX 77368 (0.1-1.0 microgram) and CG 3509 (0.1-1.0 microgram) also reversed the pentobarbitone-induced sleeping time. In contrast, TRH (5 micrograms) injected into the striatum had no effect on the pentobarbitone-induced sleeping time, and CG 3509 (0.1 microgram) and RX 77368 (0.1 microgram) had weaker effects following intrastriatal injection compared to injection of these analogues into the nucleus accumbens and septum. Measurements of core temperature and respiration rate in rats following intra-accumbens or septal injection of TRH, CG 3509 and RX 77368 showed these peptides to reverse pentobarbitone-induced hypothermia and stimulate respiration rate. However, while intrastriatal injections of CG 3509 and RX 77368 caused an increase in respiration rate they had no effect on core temperature. These results suggest a close association between peptide-induced respiratory stimulation and reversal of pentobarbitone-induced anaesthesia. Since intra-accumbens and septal injection of dopamine (20-100 micrograms) failed to reverse anaesthesia, it is unlikely that the peptide-induced responses are mediated via dopamine release.

Neuropharmacological studies in rodents on the action of RX 781094, a new selective alpha 2-adrenoceptor antagonist

Several neuropharmacological effects of RX 781094, a new selective alpha 2-adrenoceptor antagonist, have been investigated in rodents. In rats, RX 781094 (0.1-1.0 mg kg-1, i.v.) produced a rapid dose-related reversal of cortical EEG synchronisation and behavioural sedation, induced by clonidine or the more selective alpha 2-adrenoceptor agonist, guanoxabenz. The alpha 2-adrenoceptor antagonists yohimbine and mianserin were also effective in blocking guanoxabenz-induced EEG synchronisation but had a lower potency than did RX 781094. In specificity experiments, RX 781094 (1.0 mg kg-1, i.v.) failed to antagonise the EEG synchronisation and pronounced behavioural sedation induced by the CNS depressant sodium pentobarbitone (15 mg kg-1, i.v.). In mice, pretreatment (i.v. or p.o.) with RX 781094 inhibited in a dose-dependent way both guanoxabenz-induced behavioural hypoactivity and clonidine-induced hypothermia. By itself, RX 781094 had no effect on the temperature of normal mice. In sleep-waking studies in rats, RX 781094 (0.1 and 1.0 mg kg-1, i.v.) had no measurable stimulant or depressant effect on the CNS, in contrast to (+)-amphetamine (1.0 mg kg-1, i.v.) which elicited marked CNS stimulation. These results support the conclusion that RX 781094 is a potent antagonist at central alpha 2-adrenoceptors.