Biological Psychiatry Congress 2015

<p><strong>List of Abstract Titles and authors:<br /></strong></p><p><strong>1. Psychosis: A matter of mental effort?</strong></p><p>M Borg, Y Y van der Zee, J H Hsieh, H Temmingh, D J Stein, F M Howells</p><p><strong>2.In search of an affordable, effective post-discharge intervention: A randomised control trial assessing the influence of a telephone-based intervention on readmissions for patients with severe mental illness in a developing country</strong></p><p><strong></strong>U A Botha, L Koen, M Mazinu, E Jordaan, D J H Niehaus</p><p><strong>3. The effect of early abstinence from long-term methamphetamine use on brain metabolism using 1H-magnetic resonance spectro-scopy (1H-MRS)</strong></p><p>A Burger, S Brooks, D J Stein, F M Howells</p><p><strong>4. The effect of <em>in utero exposure </em>to methamphetamine on brain metabolism in childhood using 1H-magnetic resonance spectroscopy (1H-MRS)</strong></p><p>A Burger, A Roos, M Kwiatkowski, D J Stein, K A Donald, F M Howells</p><p><strong>5. A prospective study of clinical, biological and functional aspects of outcome in first-episode psychosis: The EONKCS Study</strong></p><p><strong></strong>B Chiliza, L Asmal, R Emsley</p><p><strong>6. Stimulants as cognitive enhancers - perceptions v. evidence in a very real world</strong></p><p><strong></strong>H M Clark</p><p><strong>7. Pharmacogenomics in antipsychotic drugs</strong></p><p><strong></strong>Ilse du Plessis</p><p><strong>8. Serotonin in anxiety disorders and beyond</strong></p><p><strong></strong>Ilse du Plessis</p><p><strong>9. HIV infection results in ventral-striatal reward system hypo-activation during cue processing</strong></p><p><strong></strong>S du Plessis, M Vink, J A Joska, E Koutsilieri, A Bagadia, D J Stein, R Emsley</p><p><strong>10. Disease progression in schizophrenia: Is the illness or the treatment to blame?</strong></p><p>R Emsley, M J Sian</p><p><strong>11. Serotonin transporter variants play a role in anxiety sensitivity in South African adolescents</strong></p><p> S M J Hemmings, L I Martin, L van der Merwe, R Benecke, K Domschke, S Seedat</p><p><strong>12. Iron deficiency in two children diagnosed with multiple sclerosis: Report on whole exom sequencing</strong></p><p><strong></strong>S Janse van Rensburg, R van Toorn, J F Schoeman, A Peeters, L R Fisher, K Moremi, M J Kotze</p><p><strong>13. Benzodiazepines: Practical pharmacokinetics</strong></p><p><strong></strong>P Joubert</p><p><strong>14. What to consider when prescribing psychotropic medications</strong></p><p><strong></strong>G Lippi</p><p><strong>15. Current prescribing practices for obsessive-compulsive disorder in South Africa: Controversies and consensus</strong></p><p><strong></strong>C Lochner, L Taljaard, D J Stein</p><p><strong>16. Correlates of emotional and behavioural problems in children with preinatally acquired HIV in Cape Town, South Africa</strong></p><p><strong></strong>K-A Louw, N Phillips, JIpser, J Hoare</p><p><strong>17. The role of non-coding RNAs in fear extinction</strong></p><p><strong></strong>S Malan-Muller, L Fairbairn, W M U Daniels, M J S Dashti, E J Oakleley, M Altorfer, J Harvey, S Seedat, J Gamieldien, S M J Hemmings</p><p><strong>18. An analysis of the management og HIV-mental illness comorbidity at the psychiatric unit of the Dr George Mukhari Academic Hospital</strong></p><p><strong></strong>M L Maodi, S T Rataemane, T Kyaw</p><p><strong>19. The identification of novel genes in anxiety disorders: A gene X environment correlation and interaction study</strong></p><p><strong></strong>N W McGregor, J Dimatelis, S M J Hemmings, C J Kinnear, D J Stein, V Russel, C Lochner</p><p><strong>20. Collaborations between conventional medicine and traditional healers: Obstacles and possibilities</strong></p><p><strong></strong>G Nortje, S Seedat, O Gureje</p><p><strong>21. Thought disorder and form perception: Relationships with symptoms and cognitive function in first-episode schizophrenia</strong></p><p>M R Olivier, R Emsley</p><p><strong>22. Investigating the functional significance of genome-wide variants associated with antipsychotic treatment response</strong></p><p><strong></strong>E Ovenden, B Drogemoller, L van der Merwe, R Emsley, L Warnich</p><p><strong>23. The moral and bioethical determinants of "futility" in psychiatry</strong></p><p><strong></strong>W P Pienaar</p><p><strong>24. Single voxel proton magnetic resonance spectroscopy (1H-MRS) and volumetry of the amylgdala in social anxiety disorder in the context of early developmental trauma</strong></p><p>D Rosenstein, A T Hess, J Zwart, F Ahmed-Leitao, E Meintjies, S Seedat</p><p><strong>25. Schizoaffective disorder in an acute psychiatric unit: Profile of users and agreement with Operational Criteria (OPCRIT)</strong></p><p><strong></strong>R R Singh, U Subramaney</p><p><strong>26. The right to privacy and confidentiality: The ethics of expert diagnosis in the public media and the Oscar Pistorius trial</strong></p><p><strong></strong>C Smith</p><p><strong>27. A birth cohort study in South Africa: A psychiatric perspective</strong></p><p>D J Stein</p><p><strong>28. 'Womb Raiders': Women referred for observation in terms of the Criminal Procedures Act (CPA) charged with fetal abduction and murder</strong></p><p><strong></strong>U Subramaney</p><p><strong>29. Psycho-pharmacology of sleep wake disorders: An update</strong></p><p>R Sykes</p><p><strong>30. Refugee post-settlement in South Africa: Role of adjustment challenges and family in mental health outcomes</strong></p><p><strong></strong>L Thela, A Tomita, V Maharaj, M Mhlongo, K Jonathan</p><p><strong>31. Dstinguishing ADHD symptoms in psychotic disorders: A new insight in the adult ADHD questionnaire</strong></p><p>Y van der Zee, M Borg, J H Hsieh, H Temmingh, D J Stein, F M Howells</p><p><strong>32. Oscar Pistorius ethical dilemmas in a trial by media: Does this include psychiatric evaluation by media?</strong></p><p>M Vorster</p><p><strong>33. Genetic investigation of apetite aggression in South African former young offenders: The involvement of serotonin transporter gene</strong></p><p>K Xulu, J Somer, M Hinsberger, R Weierstall, T Elbert, S Seedat, S Hemmings</p><p><strong>34. Effects of HIV and childhood trauma on brain morphemtry and neurocognitive function</strong></p><p>G Spies, F Ahmed-Leitao, C Fennema-Notestine, M Cherner, S Seedat</p><p><strong>35. Measuring intentional behaviour normative data of a newly developed motor task battery</strong></p><p><strong></strong>S Bakelaar, J Blampain, S Seedat, J van Hoof, Y Delevoye-Turrel</p><p><strong>36. Resilience in social anxiety disorder and post-traumatic stress disorder in the context of childhood trauma</strong></p><p>M Bship, S Bakelaar, D Rosenstein, S Seedat</p><p><strong>37. The ethical dilemma of seclusion practices in psychiatry</strong></p><p>G Chiba, U Subramaney</p><p><strong>38. Physical activity and neurological soft signs in patients with schizophrenia</strong></p><p>O Esan, C Osunbote, I Oladele, S Fakunle, C Ehindero</p><p><strong>39. A retrospective study of completed suicides in the Nelson Mandela Bay Metropolitan Area from 2008 to 2013 - preliminary results</strong></p><p><strong></strong>C Grobler, J Strumpher, R Jacobs</p><p><strong>40. Serotonin transporter variants play a role in anxiety sensitivity in South African adolescents</strong></p><p><strong></strong>S M J Hemmings, L I Martin, L van der Merwe, R Benecke, K Domschke, S Seedat</p><p><strong>41. Investigation of variants within antipsychotic candidate pharmacogenes associated with treatment outcome</strong></p><p>F Higgins, B Drogmoller, G Wright, L van der Merwe, N McGregor, B Chiliza, L Asmal, L Koen, D Niehaus, R Emsley, L Warnich</p><p><strong>42. Effects of diet, smoking and alcohol consumption on disability (EDSS) in people diagnosed with multiple sclerosis</strong></p><p>S Janse van Rensburg, W Davis, D Geiger, F J Cronje, L Whati, M Kidd, M J Kotze</p><p><strong>43. The clinical utility of neuroimaging in an acute adolescnet psychiatric inpatient population</strong></p><p><strong></strong>Z Khan, A Lachman, J Harvey</p><p><strong>44. Relationships between childhood trauma (CT) and premorbid adjustment (PA) in a highly traumatised sample of patients with first-episode schizophrenia (FES</strong>)</p><p>S Kilian, J Burns, S Seedat, L Asmal, B Chiliza, S du Plessis, R Olivier, R Emsley</p><p><strong>45. Functional and cognitive outcomes using an mTOR inhibitor in an adolescent with TSC</strong></p><p>A Lachman, C van der Merwe, P Boyes, P de Vries</p><p><strong>46. Perceptions about adolescent body image and eating behaviour</strong></p><p><strong></strong>K Laxton, A B R Janse van Rensburg</p><p><strong>47. Clinical relevance of FTO rs9939609 as a determinant of cardio-metabolic risk in South African patients with major depressive disorder</strong></p><p>H K Luckhoff, M J Kotze</p><p><strong>48. Childhood abuse and neglect as predictors of deficits in verbal auditory memory in non-clinical adolescents with low anxiety proneness</strong></p><p>L Martin, K Martin, S Seedat</p><p><strong>49. The changes of pro-inflammatory cytokines in a prenatally stressed febrile seizure animal model and whether <em>Rhus chirindensis</em> may attenuate these changes</strong></p><p><strong></strong>A Mohamed, M V Mabandla, L Qulu</p><p><strong>50. Influence of TMPRSS6 A736v and HFE C282y on serum iron parameters and age of onset in patients with multiple sclerosis</strong></p><p><strong></strong>K E Moremi, M J Kotze, H K Luckhoff, L R Fisher, M Kidd, R van Toorn, S Janse van Rensburg</p><p><strong>51. Polypharmacy in pregnant women with serious mental illness</strong></p><p>E Thomas, E du Toit, L Koen, D Niehaus</p><p><strong>52. Infant attachment and maternal depression as predictors of neurodevelopmental and behavioural outcomes at follow-up</strong></p><p>J Nothling, B Laughton, S Seedat</p><p><strong>53. Differences in abuse, neglect and exposure to community violence in adolescents with and without PTSD</strong></p><p><strong></strong>J Nothling, S Suliman, L Martin, C Simmons, S Seedat</p><p><strong>54. Assessment of oxidative stress markers in children with autistic spectrum disorders in Lagos, Nigeria</strong></p><p><strong></strong>Y Oshodi, O Ojewunmi, T A Oshodi, T Ijarogbe, O F Aina, J Okpuzor, O C F E A Lesi</p><p><strong>55. Change in diagnosis and management of 'gender identity disorder' in pre-adolescent children</strong></p><p>S Pickstone-Taylor</p><p><strong>56. Brain network connectivity in women exposed to intimate partner violence</strong></p><p>A Roos, J-P Fouche, B Vythilingum, D J Stein</p><p><strong>57. Prolonged exposure treatment for PTSD in a Third-World, task-shifting, community-based environment</strong></p><p>J Rossouw, E Yadin, I Mbanga, T Jacobs, W Rossouw, D Alexander, S Seedat</p><p><strong>58. Contrasting effects of early0life stress on mitochondrial energy-related proteins in striatum and hippocampus of a rat model of attention-deficit/ hyperactivity disorder</strong></p><p><strong></strong>V Russell, J Dimatelis, J Womersley, T-L Sterley</p><p><strong>59. Attention-deficit hyperactivity disorder in adults: A South African perspective</strong></p><p>R Schoeman, M de Klerk, M Kidd</p><p><strong>60. Cognitive function in women with HIV infection and early-life stress</strong></p><p>G Spies, C Fennema-Notestine, M Cherner, S Seedat</p><p><strong>61. Changes in functional connectivity networks in bipolar disorder patients after mindfulness-based cognitic therapy</strong></p><p>J A Starke, C F Beckmann, N Horn</p><p><strong>62. Post-traumatic stress disorder, overweight and obesity: A systematic review and meta-analysis</strong></p><p><strong></strong>S Suliman, L Anthonissen, J Carr, S du Plessis, R Emsley, S M J Hemmings, C Lochner, N McGregor L van den Heuvel, S Seedat</p><p><strong>63. The brain and behaviour in a third-trimester equivalent animal model of fetal alcohol spectrum disorders</strong></p><p>P C Swart, C B Currin, J J Dimatelis, V A Russell</p><p><strong>64. Irritability Assessment Model (IAM) to monitor irritability in child and adolescent psychiatric disorders.</strong></p><p>D van der Westhuizen</p><p><strong>65. Outcome of parent-adolescent training in chilhood victimisation: Adaptive functioning, psychosocial and physiological variables</strong></p><p>D van der Westhuizen</p><p><strong>66. The effect of ketamine in the Wistar-Kyoto and Sprague Dawley rat models of depression</strong></p><p>P J van Zyl, J J Dimatelis, V A Russell</p><p><strong>67. Investigating COMT variants in anxiety sensitivity in South African adolescents</strong></p><p>L J Zass, L Martin, S Seedat, S M J Hemmings</p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p><p><strong><br /></strong></p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p>

Biological Tissue Adhesion to Ion Implanted Surfaces

Results of preliminary investigations on varying the adhesion and growth behaviour of osteoblast-like cells on silicon are presented. Significant changes in growth behaviour are obtained by implanting oxygen or by growing a thermal oxide on the surface. The objective of the work is to modify tissue adhesion to materials used as prosthetic devices.

Alcohol use after liver transplantation in alcoholics: a clinical cohort follow-up study

The purposes of this study were to determine among a cohort of long-term alcoholic survivors after liver transplantation (1) the incidence of alcohol use, (2) its effect on allograft integrity and extrahepatic health, and (3) the validity of the pretransplant alcohol prognosis screening process. Retrospective clinical cohort study of all alcoholic patients undergoing orthotopic liver transplantation at a single center from February 1987 until January 1991 with follow-up through December 1994, giving a median duration of follow-up of 63 months (range, 6-89 months). Multidisciplinary liver transplantation program at a tertiary-care academic medical center. Fifty alcoholic, long-term liver transplant recipients. The frequency of alcohol relapse, defined as any alcohol use in the period after transplantation, was determined by two questionnaire studies and by clinical follow-up. Allograft integrity was assessed by coded review of serial percutaneous allograft biopsies. Potential systemic effects of alcohol relapse were assessed by chart review. The alcohol prognosis screening process was evaluated by retrospectively comparing pretransplant estimates of putative indicators of alcoholism prognosis in posttransplant alcohol users and abstainers. Thirty-three recipients (66%) consistently denied any alcohol use throughout the duration of posttransplant follow-up, whereas 17 (34%) were identified as having consumed alcohol at least once since the transplant. There were no significant differences at the time of evaluation between abstainers and alcohol users in age, sex distribution, severity of liver dysfunction, median duration of abstinence, or University of Michigan alcoholism prognosis score. The median interval from transplantation to alcohol relapse was 17 months, with a range of 3 to 45 months. Recurrent alcohol use was associated with significant medical complications sufficient to require admission to the hospital in 6 patients. One patient died of graft dysfunction, noncompliance with immunosuppressant medications, and presumed graft rejection while drinking. Mild or progressive hepatitis, which was the most common abnormality in posttransplant liver biopsy findings, was equally distributed between both alcohol users and abstainers and sometimes occurred in the absence of antibody to hepatitis C virus antibodies. There was a similar frequency of biopsy-proven acute cellular rejection in alcohol users and abstainers. Typical histological features of alcoholic liver injury were present in posttransplant biopsies from 1 alcohol user only. Alcohol use by alcoholics is uncommon in the first 5 years after liver transplantation, and alcohol-associated liver injury is unusual. Mild nonspecific hepatitis is common in both alcohol users and nonusers alike. Among a small subset of alcoholic transplant recipients, drinking behavior after liver transplantation is associated with considerable morbidity, requiring hospital admissions and occasionally leading to graft loss and death.

Acute cellular rejection after liver transplantation: variability, morbidity, and mortality

Acute cellular rejection of the allograft is a potentially serious complication after liver transplantation, yet its true incidence is unknown. We therefore investigated the frequency of acute cellular rejection reported by transplant centers and its impact on morbidity and mortality. Morbidity was defined as duration of hospitalization. Of 200 articles screened, 18 were selected for inclusion in the study database, in which there was a total of 1,437 patients who received transplants. All contained more than 20 patients and invariably used histopathology for diagnosis of acute cellular rejection. These reports included all transplant patients within a fixed period and sufficient data to determine the incidence of acute cellular rejection. Morbidity data were obtained from our previous series. The mean incidence of acute cellular rejection in all centers was 49.8% (range between centers, 24% to 80%). Two immunosuppressive cohorts were identified: high-dose cyclosporine induction (> or = 5 mg/kg/d) and low-dose cyclosporine induction (< or = 4 mg/kg/d). Acute cellular rejection was reported in 27.0% of the high-dose group and 63.6% of the low-dose group, P = .0001. Strict adherence to Snover's histological criteria for acute cellular rejection did not alter the reported mean incidence. Frequency of acute cellular rejection was 45.2% (range between centers, 24% to 80%) in 8 studies that used Snover's criteria, and 51.6% (range between centers, 37% to 80%) in 10 studies that did not. There was no correlation between mortality and incidence of acute cellular rejection in the 9 studies that reported survival (R2 = .105). Morbidity data showed that the average length of initial hospitalization after transplantation for patients with acute cellular rejection was 52.4 +/- 8.3 (range, 14 to 124) days, in contrast to 28.3 +/- 2.3 (range, 9 to 87) days for patients with no rejection. P = .0008. The total number of hospital days in the first 6 months for patients with acute cellular rejection was 55.6 +/- 8.6 (range, 14 to 124) days and with no rejection, was 37.7 +/- 3.1 (range, 9 to 99) days. P = .0232. The incidence of acute cellular rejection varies widely among transplant centers, regardless of the use of Snover's criteria. Acute cellular rejection appeared to be less frequent in programs using high-dose cyclosporine induction regimens. The presence of acute cellular rejection seemed to have no correlation with mortality but significantly increased morbidity and therefore the cost of transplantation.

The effect of ion implantation on cellular adhesion

As there are only a finite number of materials suitable for orthopaedic reconstruction, considerable effort has been devoted recently to investigating ways of altering the surface chemistry of prosthetic materials without altering their bulk properties. Ion beam implantation is one such technique which is appropriate for orthopaedic reconstructive materials. This paper investigates the early effect of ion beam modification on cellular attachment of bone derived cells using a prototype device which measures the strength of attachment of individual cells to a silicon substratum. The results point to several conclusions. (1) There is no evidence that ion beam implantation with nitrogen, phosphorus, manganese or magnesium produces increased adhesion of human bone derived cells. (2) Surface etching with hydrofluoric acid, electron bombardment and thermal oxidation increases the strength of attachment between cells and substrata. (3) There is a correlation between wettability and rate of cellular attachment to oxygen implanted substrata during the first 2 h after cellular seeding. However, the increase in cellular attachment cannot be entirely explained by the change in critical surface tension or via increased fibronectin attachment to the substrata.

Relation between chest expansion, pulmonary function, and exercise tolerance in patients with ankylosing spondylitis

Thirty three patients with definite ankylosing spondylitis (AS) were examined to establish the relation between restriction of chest expansion, limitation of lung function, and working capacity or exercise tolerance. As in previous studies there was a significant association between chest expansion and lung vital capacity. There was also a significant association between vital capacity and exercise tolerance as measured by a subject's maximum oxygen capacity (VO2max). Both vital capacity and VO2max were expressed as a percentage of predicted normal values using patients' height before disease. In this study chest expansion did not have a significant effect on exercise tolerance. The results suggested that patients who took a modest amount of exercise regularly could maintain a satisfactory work capacity despite very restricted spinal and chest wall mobility. It is recommended that greater emphasis should be given to encouraging patients with AS to maintain cardiorespiratory fitness as well as spinal mobility.

A micromechanical technique for monitoring cell-substrate adhesiveness: measurements of the strength of red blood cell adhesion to glass and polymer test surfaces

We report a novel method for rapid comparison of the relative strength of adhesion of cells to different solid surfaces. A vertically oscillating micropipette is brought above an individual cell in such a manner that it makes contact with the cell at the lower limit of its travel. The pressure within the micropipette is gradually reduced until the cell attaches to the micropipette by suction and is lifted from the solid surface. The reduction in pressure required to detach a cell depends on the specific cell/substrate combination and serves as a relative measure of the strength of cell adhesion. A particular advantage of this approach over conventional methods is the ability to select particular cells from a population. As a test of the reproducibility of the method and its ability to distinguish the strength of adhesion of cells to different solid surfaces, we have used it to measure the adhesiveness of human red blood cells to hydrophilic glass, tissue culture grade polystyrene, polyethylene terephthalate, and polymethyl methacrylate. We find that results for the same surface are highly reproducible and that the method is capable of distinguishing small differences in the adhesiveness of red blood cells to the above surfaces.

Questionnaire assessment of patient satisfaction with lower limb orthoses from a district hospital

A questionnaire survey of patient satisfaction with the provision of lower limb orthoses from a district general hospital was conducted. Lower limb orthoses included "made-to-measure" footwear, knee braces and ankle-foot-orthoses (AFO's). Prescriptions for footwear and AFO's during a one year period, and knee braces over a two year period were assessed. The survey did not confine itself to a single medical condition. The level of patient dissatisfaction with the various orthoses was as follows: AFO's 16%, footwear 24%, knee braces 42%. This level of dissatisfaction amounts to considerable financial waste. Although several recommendations can be made on the basis of these results, this study highlights the need for more detailed audit and research into the prescription and provision of orthoses in order to reduce this wastage.

Direct measurement of cell detachment force on single cells using a new electromechanical method

We describe a new device in which an accurately measured force is applied to individual adherent cells while the topography of the adhesion zone is simultaneously monitored. The force is applied via a flexible glass micropipette, attached by suction to the cell under study, and is calculated directly from the measured pipette deflection. Regions of close contact in the adhesion zone are observed using interference reflection microscopy. We have used the device to measure the force required to detach human red blood cells from hydrophobic and hydrophilic glass surfaces, and to detach Dictyostelium discoideum amoebae from a hydrophobic glass surface. The measured forces per unit length of contact perimeter are within an order of magnitude of the tensions required for membrane rupture.

HLA antigens in palindromic rheumatism and palindromic onset rheumatoid arthritis

Fifty patients who presented with typical palindromic rheumatism of at least 6 months' duration were tissue-typed for HLA A, B, C antigens. DR typing was also performed but was not possible for technical reasons in three patients. Twenty-three patients who had progressed to definite or classical rheumatoid arthritis (RA) after a mean interval of 5 years were compared with 20 patients whose palindromic attacks had persisted over a similar period. Both groups showed a significantly higher frequency of DR4 antigen than a control population. The RA group also showed an increased frequency of DR1. There was no significant difference in the frequency of DR4 or any other DR antigen between the two patient groups. The frequency of B27 antigen was significantly higher in the palindromic group compared with the controls. It is suggested that although DR4 may be associated with a tendency to inflammatory joint problems, environmental or other unrelated genetic factors may be more important in determining the progression of palindromic rheumatism to RA.

Osmotic control of bilayer fusion

We have used photography and capacitance measurement to monitor the steps in the interaction and eventual fusion of optically black lipid bilayers (BLMs), hydrostatically bulged to approximately hemispherical shape and pushed together mechanically. A necessary first step is drainage of aqueous solution from between the bilayers to allow close contact of the bilayers. The drainage can be controlled by varying the osmotic difference across the bilayers. If the differences are such as to remove water from between the bilayers, fusion occurs after a time that depends on the net osmotic difference and the area of contact. If there is an osmotic flow of water into the space between the bilayers, fusion never occurs. In the fusion process, a single central bilayer forms from the original apposed pair of bilayers. The central bilayer may later burst to allow mixing of the two volumes originally bounded by the separate bilayer; the topological equivalent of exocytosis.

Environment of solubilized molecules in bile salt micelles

Bile salt micelles, and mixed bile salt-phospholipid micelles, solubilize cholesterol and dietary lipids. As a first step in a study of the mechanism of solubilization by bile salt micelles, we have studied the solubilization of two fluorescence probe molecules and an electron spin resonance probe molecule. One fluorescence probe, 1-methylanthracene, is free to rotate in the molecular plane when solubilized. The other probe molecules, N-phenylnaphthalen-1-amine and 4-(11-carboxy-1-hexylundec-1-yl)- 2,2,6,6-tetramethylpiperidin-1-yloxy, are greatly restricted in mobility when solubilized. The 1-methylanthracene molecule is planar, and is small enough to fit into the hydrophobic region of a bile salt micelle without protruding. The other probe molecules used do not fit these criteria. We suggest that small planar molecules in general may be free to rotate (about an axis perpendicular to the plane) in bile salt micelles. Thus solubilization of planar molecules would be entropically favoured. In particular, cholesterol is a planar molecule known to be highly solubilized by bile salt micelles. The cholesterol molecule meets the above criteria, and thus we suggest that its solubilization is entropically favoured over non-planar molecules.

Interaction of water with egg lecithin in benzene solution

Benzene solutions of purified egg lecithin, with small amounts of water added, have been examined by 60 MGz and 100 MHz NMR spectroscopy, infrared spectrophotometry and phase contrast microscopy. The transverse relaxation times of the water, N-methyl and O--H protons are dependent on water concentration. This dependence changes sharply for the water proton at a level of one water molecule per lecithin monohydrate molecule. These results do not fully agree with those reported by other workers. Four mathematical models are examined which could account for the behaviour of the water protons. Models which assume a constant transverse relaxation time for water protons above a level of one water molecule per lecithin molecule cannot predict the behaviour observed. It is sufficient to assume that water protons above this concentration have a single relaxation time which is a linear function of water concentration. The added water associates primarily with the phosphate in the lecithin head group. Above nine water molecules per lecithin monohydrate molecule free water is present in the system.