The influence of native porcine gastric mucus gel on hydrogen ion diffusion: the effect of potentially ulcerogenic agents

Experiments were carried out to investigate the ability of native gastric mucus gels to retard hydrogen ion diffusion. Mucus held between two polycarbonate membrane filters in a diffusion cell, separating equimolar solutions of NaCl and HCl, significantly reduced the rate of hydrogen ion diffusion and increased the time for the mean hydrogen ion front to traverse the mucus compartment (lag time) when compared to an unstirred layer of saline (P less than 0.01). N-acetylcysteine, sodium taurodeoxycholate and acetylsalicylic acid significantly increased the diffusion rate (P less than 0.025); the lag time was significantly reduced by N-acetylcysteine (P less than 0.001). In addition mucus gels were found to have buffering capacity at a pH greater than 2. These observations suggest that native gastric mucus gels can retard hydrogen ion diffusion and that this retardation of diffusion is reduced by agents which are potentially damaging to the gastric mucosa.

Membrane damage by bile salts: the protective function of phospholipids

The direct toxicity of sodium deoxycholate (SDC) and lysophosphatidylcholine (LPC) to biological membranes was assessed by measurement of goldfish overturn time. When phosphatidylcholine (PC) was incorporated into the aqueous media, the toxicity of both SDC and LPC was reduced, as indicated by increased overturn time. Fish were also pretreated for various times in media containing (a) 1 mM SDC and (b) 1 mM SDC with 1 mM PC. Subsequent transfer to solution, 100 mg litre-1 quinalbarbitone sodium showed that reciprocal overturn times for fish treated using method (a) increased linearly with duration of pretreatment up to a limiting value, obtained after 20 min exposure; 40 min exposure to 1 mM SDC was directly toxic. Fish pretreated using regimen (b) survived longer when challenged with barbiturate, and the reciprocal overturn times were a linear function of time of pretreatment up to at least 40 min. PC also provided protection against membrane damage caused by the synthetic surfactant sodium dodecyl sulphate. Mixed micelle formation between PC and surfactant is thought to account for the protective effects. The results are of significance in the consideration of reflux hypothesis for the aetiology of gastric ulceration and also the possible formulation of drug delivery systems intended to enhance absorption whilst minimizing gastrointestinal damage.

The efficacy of acupuncture as an aid to stopping smoking

The present study examines the usefulness of acupuncture as an aid to stopping smoking. Results from 405 subjects show acupuncture can help between 5 and 15 percent of the population to stop smoking for at least six months. Using chronically implanted press needles, previously reported 'effective' auricular acupuncture points for smoking cessation are shown to be no better than 'placebo' auricular points. Additional electroacupuncture on the hand neither increases the probability of stopping smoking nor enhances the reduction in smoking at three week, three month or six month follow-up periods. It is therefore likely that a large psychological component is attached to acupuncture to stop people smoking.

The solubilization of progesterone by mixed bile salt-phospholipid sols

The solubility of progesterone was determined in several different bile salt-phospholipid mixtures, and it is concluded that: (1) The solubility in unconjugated bile salts is greater than in the conjugated analogues, and the solubility in deoxycholate solutions is twice that in cholate solutions. (2) Substitution of hydroxyl groups in the 11 and 21 positions of progesterone increases solubility, whilst substitution in the 17-position decreases solubility in bile salt solutions. (3) Progesterone solubility in mixed bile salt solutions is proportional to the mole ratio of the surfactant mixture. (4) Sodium deoxycholate (SDC)-phospholipid sols show no such linear solubilizing properties; a minimum occurring at a mole ratio of SDC to phospholipid of 1 : 4. (5) There is a break in the solubility curve of progesterone in lysophosphatidycholine (LPC)/phosphatidylcholine (PC) mixtures at a mole ratio of 65 : 35 coincident with maximum viscosity. (6) Introduction of SDC into LPC/PC mixtures results in decreased progesterone solubility.

Direct effect of bile salts and phospholipids on the physical properties of mucus

Reflux of duodenal contents into the stomach has been implicated in the disruption of mucosal defence and the subsequent occurrence of gastric ulcer. The change produced in the rheological properties following the addition of bile salts and phospholipids to mucus samples was used to assess resultant structural changes. Sodium deoxycholate, sodium taurodeoxycholate, sodium glycocholate, and lysophosphatidylcholine decreased both viscosity and elasticity, indicating that structural breakdown had occurred, whereas phosphatidylcholine could not be shown to have any effect. It is therefore suggested that some of the ulcerogenic activity of naturally occurring surfactants may be associated with their ability directly to reduce mucus consistency.