Perioperative knowledge, self-efficacy and clinical practices related to postoperative delirium care in older people across geographical regions in Australia.

INTRODUCTION: In older people undergoing surgery, there is a lower tolerance for complications. This highlights the need for documented clinical practices on proper prevention, pre-screening and management of complications such as postoperative delirium (POD). Evidence-based clinical practice guidelines exist for delirium management; however, the management of delirium in clinical settings differs widely. OBJECTIVE: This study aims to develop an understanding of the knowledge, components of self-efficacy (confidence/competence), and clinical practice related to POD care among preoperative and recovery nurses across different types of geographical locations in Australia. DESIGN: A 27-item online survey was sent out to professional associations focused on perioperative care across Australia. The participants included practicing registered nurses specialising in perioperative care. The main outcome measures were Knowledge, confidence/competence and clinical practice relating to POD care in older patients. FINDINGS: Respondents were categorised into two groups-major cities and rural and remote. Mean age was 46.3 years for respondents in Australian major cities and 49.5 for the comparison group. There was a statistically significant difference between Australian major cities and 'rural and remote' in confidence in detecting hyperactive delirium, 25.2% versus 11.7% respectively as well as managing hyperactive delirium, 13.8% versus 1.7%, respectively. Similar results were also observed on hypoactive delirium. Respondents from both groups did not mirror the ideal situation in managing a hyperactive delirium. DISCUSSION: Results from this study are inconclusive and there is no clear-cut observation in clinical practice or knowledge between the two geographical categories in this study. CONCLUSION: The absence of a distinct strategy with POD prevention highlights the need for a uniform approach and consensus on POD prevention and management in older people. This can be achieved by creating more awareness and education through professional development related to POD.

Incidence of postoperative delirium in older adults undergoing surgical procedures: A systematic literature review and meta-analysis.

BACKGROUND: With the increase in life expectancy around the globe, the incidence of postoperative delirium (POD) among older people (≥65 years) is growing. Previous studies showed a wide variation in the incidence of POD, from 4% to 53%, with a lack of specific evidence about the incidence of POD by specific surgery type among older people. The aim of this systematic review and meta-analysis was to determine the incidence of POD by surgery type within populations 65 years and over. METHODS: Databases including PubMed, Cochrane library, Embase, and CINAHL were searched until October 2020. Due to the relatively higher number of meta-analyses undertaken in this area of research, a streamlined systematic meta-analysis was proposed. RESULTS: A total of 28 meta-analyses (comprising 284 individual studies) were reviewed. Data from relevant individual studies (n = 90) were extracted and included in the current study. Studies were grouped into eight surgery types and the incidence of POD for orthopedic, vascular, spinal, cardiac, colorectal, abdominal, urologic, and mixed surgeries was 20%, 14%, 13%, 32%, 14%, 30%, 10%, and 26%, respectively. POD detection instruments were different across the studies, with Confusion Assessment Method (CAM & CAM-ICU) being the most frequently adopted. LINKING EVIDENCE TO ACTION: This study showed that POD incidence in older people undergoing surgery varied widely across surgery type. The more complex surgeries like cardiac and abdominal surgeries were associated with a higher risk of POD. This highlights the need to include the level of surgery complexity as a risk factor in preoperative assessments.

Delirium education and post-anaesthetics care unit nurses' knowledge on recognising and managing delirium in older patients.

BACKGROUND: Postoperative delirium (POD) is a major complication following a surgical procedure. There is evidence that improving knowledge about POD could enhance POD care and patient outcomes. AIM: The study aimed to evaluate whether the amount of delirium education among registered nurses working in post-anaesthetics care units (PACU) impacts on their self-reported confidence and competence in recognising and managing delirium as well as prior knowledge on factors that influence the risk of delirium onset for older people. METHOD: The current study utilised an online survey on delirium care practice among registered nurses in PACUs. The survey consisted of 27 items. There were questions about confidence and competence in delirium care, knowledge about delirium risk factors, and ranked responses to two case scenario questions to evaluate the application of POD care. There were also demographic questions, including previous experience with delirium care education. RESULTS: A total of 336 responses were generated from registered nurses working in PACU. Our findings found substantial variability among the respondents about their delirium care education. The amount of delirium education did not influence the PACU registered nurses' confidence or competence in delirium care. In addition, previous education did not have an impact on their knowledge about delirium risk factors. DISCUSSION AND CONCLUSION: These findings suggested that the quantity of prior education about delirium did not improve the confidence, competence, knowledge, or case scenario questions of PACU registered nurses. Thus, delirium care education needs to be transformed to ensure it has a positive effect on delirium care clinical practice by registered nurses in PACU.

Optimising health care for people living with chronic kidney disease: Health-professional perspectives.

BACKGROUND: People with chronic kidney disease are often multimorbid and have complex psychosocial needs. For health professionals to deliver holistic, person-centred care to individuals and their carers living with this multifaceted disease, they are required to communicate complex information and problem solve in a multifactorial health and disease context. OBJECTIVES: To explore the perspectives and experiences of tertiary care multidisciplinary team members and primary care providers of health care to people with chronic kidney disease; identify opportunities to innovate and improve the coordinated delivery of health services. DESIGN: The qualitative study design used purposive sampling to recruit 39 health professionals, working in the primary and tertiary sector in a regional Australian health district. Participants included general practitioners, renal and general practice nurses, dietitians, nephrologists and social workers. APPROACH: The data were collected through semistructured interviews and analysed using a relativist ontological position and directed content analysis approach. Analysis of interviews was undertaken by three independent researchers and key themes were derived via consensus. FINDINGS AND CONCLUSIONS: A common goal to deliver person-centred individualised care was evident among health care professionals. However a deficit in shared understanding of the disease within and between disciplines was identified. The complex nature of chronic kidney disease requires up-skilling of health professionals to ensure patient education is targeted to individual health contexts and motivates self-management. Improved communication and comprehension might best be achieved across disciplines with an integrated approach to delivery of primary health care to individuals living with early-stage kidney disease.

Postoperative Delirium in Older Patients: A Systematic Review of Assessment and Incidence of Postoperative Delirium.

BACKGROUND: Postoperative delirium is the most common complication of surgery particularly in older patients. AIMS: The current study aimed to summarize the commonly used delirium assessment tools in assessing postoperative delirium (POD) and to estimate the incidence rates of POD. METHODS: A systematic review that included empirical cohort studies reporting the use of delirium assessment tools in assessing POD between 2000 and 2019. Five core databases were searched for eligible studies. The methodological quality assessment of the included studies was undertaken using the Joanna Briggs Institute (JBI) critical appraisal checklist to examine the risk of bias. Pooled incidence estimates were calculated using a random effects model. RESULTS: Nineteen studies with a total of 3,533 postsurgery older patients were included in this review. The confusion assessment method (CAM) and CAM-ICU were the most commonly used tools to assess POD among older postoperative patients. The pooled incidence rate of POD was 24% (95% CI [0.20, 0.29]). The pooled incidence estimates for mixed (noncardiac) surgery, orthopedic surgery, and tumor surgery were 23% (95% CI [0.15, 0.31]), 27% (95% CI [0.20, 0.33]), and 19% (95% CI [0.15, 0.22]), respectively. More than 50% of included studies used CAM to assess POD in different types of postoperative patients. Using CAM to assess delirium is less time-consuming and it was suggested as the most efficient tool for POD detection. LINKING EVIDENCE TO ACTION: We identified that CAM could be implemented in different settings for assessing POD. The incidence and risk factors for POD introduced can be used for future research to target these potential indicators. The incidence rate, risk factors, and predictors of POD explored can provide robust evidence for clinical practitioners in their daily practice.

Effect of liraglutide on neural and peripheral markers of metabolic function during antipsychotic treatment in rats.

BACKGROUND: Liraglutide is a glucagon-like peptide-1 (GLP-1) receptor agonist that prevents metabolic side effects of the antipsychotic drugs (APDs) olanzapine and clozapine through unknown mechanisms. AIM: This study aimed to investigate the effect of chronic APD and liraglutide co-treatment on key neural and peripheral metabolic signals, and acute liraglutide co-treatment on clozapine-induced hyperglycaemia. METHODS: In study 1, rats were administered olanzapine (2 mg/kg), clozapine (12 mg/kg), liraglutide (0.2 mg/kg), olanzapine + liraglutide co-treatment, clozapine + liraglutide co-treatment or vehicle for six weeks. Feeding efficiency was examined weekly. Examination of brain tissue (dorsal vagal complex (DVC) and mediobasal hypothalamus (MBH)), plasma metabolic hormones and peripheral (liver and kidney) cellular metabolism and oxidative stress was conducted. In study 2, rats were administered a single dose of clozapine (12 mg/kg), liraglutide (0.4 mg/kg), clozapine + liraglutide co-treatment or vehicle. Glucose tolerance and plasma hormone levels were assessed. RESULTS: Liraglutide co-treatment prevented the time-dependent increase in feeding efficiency caused by olanzapine, which plateaued by six weeks. There was no effect of chronic treatment on melanocortinergic, GABAergic, glutamatergic or endocannabionoid markers in the MBH or DVC. Peripheral hormones and cellular metabolic markers were unaltered by chronic APD treatment. Acute liraglutide co-treatment was unable to prevent clozapine-induced hyperglycaemia, but it did alter catecholamine levels. CONCLUSION: The unexpected lack of change to central and peripheral markers following chronic treatment, despite the presence of weight gain, may reflect adaptive mechanisms. Further studies examining alterations across different time points are required to continue to elucidate the mechanisms underlying the benefits of liraglutide on APD-induced metabolic side effects.

Multi-disciplinary and pharmacological interventions to reduce post-operative delirium in elderly patients: A systematic review and meta-analysis.

STUDY OBJECTIVE: An estimated 80% of older people undergoing surgery develop postoperative delirium (POD) making them a high-risk group. Research in this area is growing fast but there is no established consensus on strategies for POD prevention or management. A systematic review and meta-analysis were conducted to synthesise data on clinical interventions used to reduce POD among older people undergoing elective and emergency surgery. METHODS: A range of database searches generated 336 papers. A total of 25 studies met the inclusion criteria and were assessed using the Joanna Briggs Institute Critical Appraisal Checklist. The studies were undertaken across the world. RESULTS: This review identified a range of intervention approaches: comparisons between anaesthetic and sedatives agents, medication-specific interventions and multidisciplinary models of care. Results found more consistencies across multidisciplinary interventions than the pharmacological interventions. In pooled analyses, haloperidol (OR 0.74; 95% CI (confidence interval) 0.44, 1.26) was not statistically significantly associated with reduced POD incidence any more than a placebo. CONCLUSION: There is a need to implement multidisciplinary interventions, as well as collaboration between clinicians on pre- and postoperative care practices regarding pharmacological interventions to more effectively reduce and manage POD in older people.

Distribution of Glycerophospholipids in the Adult Human Lens.

In humans, the age of fibre cells differs across the ocular lens, ranging from those formed before birth in the core of the lens to those formed just prior to death in the outer cortex. The distribution of glycerophospholipids in the adult human lens should reflect this range; however, limited data currently exists to confirm this hypothesis. Accordingly, this study aimed to determine the distribution of glycerophospholipids in adult human lens using mass spectrometry imaging. To achieve this, 20-µm thick slices of two human lenses, aged 51 and 67 were analysed by matrix-assisted laser desorption ionisation imaging mass spectrometry. The data clearly indicate that intact glycerophospholipids such as phosphatidylethanolamine, phosphatidylserine, and phosphatidic acid are mainly present in the outer cortex region, corresponding to the youngest fibre cells, while lyso-phosphatidylethanolamine, likely produced by the degradation of phosphatidylethanolamine, is present in the nucleus (older fibre cells). This study adds further evidence to the relationship between fibre cell age and glycerophospholipid composition.

Factors influencing early withdrawal from a drug and alcohol treatment program and client perceptions of successful recovery and employment: a qualitative study.

BACKGROUND: Substance use disorders are a major contributor to the economic and healthcare burden in Australia. Therapeutic communities (TCs) are utilised treatment methods globally, though low program completion rates continue to represent a major obstacle in effective and sustainable drug and alcohol treatment. The aim of this study was to explore reasons for early withdrawal from TC programs and perceptions of successful recovery. This study also aimed to explore how employment and volunteering related to early exit and perceptions of successful recovery. METHODS: Semi-structured qualitative interviews were conducted with 13 ex-residents from a long-term TC program at a community-based rehab organisation in regional Australia. RESULTS: Thematic analysis revealed a complex interplay of factors contributing to early TC withdrawal, and perceptions of successful recovery from a lived experience perspective and how this was shaped by employment and volunteering. Eleven themes were identified. Three relating to reasons for joining the program, which connected with ultimate withdrawal from the program: Pre-program existing relationships, pre-program employment situation and needing a 'circuit breaker' in their life. Three relating to reasons for early withdrawal: TC program characteristics, relationships during the program and planning future employment. Five relating to perceptions of successful recovery: Improved understanding of their addiction, reduced substance use, improved physical and psychological health, relationship success and employment success. CONCLUSIONS: Reasons for leaving treatment early are multi-faceted and revolve around relationships, planning future employment and program characteristics. The influence that each plays on their decision to leave early is varied and determined by the value they assign it. Perceived success extends far beyond achieving and maintaining abstinence to encompass improved relationships, psychological and physical wellbeing, understanding of addiction and employment, studying or volunteering. Self-worth and feeling able to contribute to society through employment, study and volunteering were perceived to be essential elements of successful recovery. Clinicians, policy makers and program developers should use the extended definition of successful recovery from the ex-clients perspective when determining the clinical and economic effectiveness of TC programs.

Disrupted sphingolipid metabolism following acute clozapine and olanzapine administration.

BACKGROUND: Second generation antipsychotics (SGAs) induce glucometabolic side-effects, such as hyperglycemia and insulin resistance, which pose a therapeutic challenge for mental illness. Sphingolipids play a role in glycaemic balance and insulin resistance. Endoplasmic reticulum (ER) stress contributes to impaired insulin signalling and whole-body glucose intolerance. Diabetogenic SGA effects on ER stress and sphingolipids, such as ceramide and sphingomyelin, in peripheral metabolic tissues are unknown. This study aimed to investigate the acute effects of clozapine and olanzapine on ceramide and sphingomyelin levels, and protein expression of key enzymes involved in lipid and glucose metabolism, in the liver and skeletal muscle. METHODS: Female rats were administered olanzapine (1 mg/kg), clozapine (12 mg/kg), or vehicle (control) and euthanized 1-h later. Ceramide and sphingomyelin levels were examined using electrospray ionization (ESI) mass spectrometry. Expression of lipid enzymes (ceramide synthase 2 (CerS2), elongation of very long-chain fatty acid 1 (ELOVL1), fatty acid synthase (FAS) and acetyl CoA carboxylase 1 (ACC1)), ER stress markers (inositol-requiring enzyme 1 (IRE1) and eukaryotic initiation factor (eIF2α) were also examined. RESULTS: Clozapine caused robust reductions in hepatic ceramide and sphingolipid levels (p < 0.0001), upregulated CerS2 (p < 0.05) and ELOVL1 (+ 37%) and induced significant hyperglycemia (vs controls). In contrast, olanzapine increased hepatic sphingomyelin levels (p < 0.05 vs controls). SGAs did not alter sphingolipid levels in the muscle. Clozapine increased (+ 52.5%) hepatic eIF2α phosphorylation, demonstrating evidence of activation of the PERK/eIF2α ER stress axis. Hepatic IRE1, FAS and ACC1 were unaltered. CONCLUSIONS: This study provides the first evidence that diabetogenic SGAs disrupt hepatic sphingolipid homeostasis within 1-h of administration. Sphingolipids may be key candidates in the mechanisms underlying the diabetes side-effects of SGAs; however, further research is required.

Liraglutide prevents metabolic side-effects and improves recognition and working memory during antipsychotic treatment in rats.

BACKGROUND: Antipsychotic drugs (APDs), olanzapine and clozapine, do not effectively address the cognitive symptoms of schizophrenia and can cause serious metabolic side-effects. Liraglutide is a synthetic glucagon-like peptide-1 (GLP-1) receptor agonist with anti-obesity and neuroprotective properties. The aim of this study was to examine whether liraglutide prevents weight gain/hyperglycaemia side-effects and cognitive deficits when co-administered from the commencement of olanzapine and clozapine treatment. METHODS: Rats were administered olanzapine (2 mg/kg, three times daily (t.i.d.)), clozapine (12 mg/kg, t.i.d.), liraglutide (0.2 mg/kg, twice daily (b.i.d.)), olanzapine + liraglutide co-treatment, clozapine + liraglutide co-treatment or vehicle (Control) ( n = 12/group, 6 weeks). Recognition and working memory were examined using Novel Object Recognition (NOR) and T-Maze tests. Body weight, food intake, adiposity, locomotor activity and glucose tolerance were examined. RESULTS: Liraglutide co-treatment prevented olanzapine- and clozapine-induced reductions in the NOR test discrimination ratio ( p < 0.001). Olanzapine, but not clozapine, reduced correct entries in the T-Maze test ( p < 0.05 versus Control) while liraglutide prevented this deficit. Liraglutide reduced olanzapine-induced weight gain and adiposity. Olanzapine significantly decreased voluntary locomotor activity and liraglutide co-treatment partially reversed this effect. Liraglutide improved clozapine-induced glucose intolerance. CONCLUSION: Liraglutide co-treatment improved aspects of cognition, prevented obesity side-effects of olanzapine, and the hyperglycaemia caused by clozapine, when administered from the start of APD treatment. The results demonstrate a potential treatment for individuals at a high risk of experiencing adverse effects of APDs.

Lipid pathway alterations in Parkinson's disease primary visual cortex.

BACKGROUND: We present a lipidomics analysis of human Parkinson's disease tissues. We have focused on the primary visual cortex, a region that is devoid of pathological changes and Lewy bodies; and two additional regions, the amygdala and anterior cingulate cortex which contain Lewy bodies at different disease stages but do not have as severe degeneration as the substantia nigra. METHODOLOGY/PRINCIPAL FINDINGS: Using liquid chromatography mass spectrometry lipidomics techniques for an initial screen of 200 lipid species, significant changes in 79 sphingolipid, glycerophospholipid and cholesterol species were detected in the visual cortex of Parkinson's disease patients (n = 10) compared to controls (n = 10) as assessed by two-sided unpaired t-test (p-value <0.05). False discovery rate analysis confirmed that 73 of these 79 lipid species were significantly changed in the visual cortex (q-value <0.05). By contrast, changes in 17 and 12 lipid species were identified in the Parkinson's disease amygdala and anterior cingulate cortex, respectively, compared to controls; none of which remained significant after false discovery rate analysis. Using gas chromatography mass spectrometry techniques, 6 out of 7 oxysterols analysed from both non-enzymatic and enzymatic pathways were also selectively increased in the Parkinson's disease visual cortex. Many of these changes in visual cortex lipids were correlated with relevant changes in the expression of genes involved in lipid metabolism and an oxidative stress response as determined by quantitative polymerase chain reaction techniques. CONCLUSIONS/SIGNIFICANCE: The data indicate that changes in lipid metabolism occur in the Parkinson's disease visual cortex in the absence of obvious pathology. This suggests that normalization of lipid metabolism and/or oxidative stress status in the visual cortex may represent a novel route for treatment of non-motor symptoms, such as visual hallucinations, that are experienced by a majority of Parkinson's disease patients.

Fatty Acid uptake and incorporation into phospholipids in the rat lens.

PURPOSE: Phospholipids are a major component of lens fiber cells and influence the activity of membrane proteins. Previous investigations of fatty acid uptake by the lens are limited. The purpose of the present study was thus to determine whether exogenous fatty acids could be taken up by the rat lens and incorporated into molecular phospholipids. METHODS: Lenses were incubated with fluorescently labeled palmitic acid and then analyzed by confocal microscopy. Concurrently, lenses incubated with either fluorescently labeled palmitic acid or the more physiologically relevant (13)C(18)-oleic acid were sectioned into nuclear and cortical regions and analyzed by highly sensitive and structurally selective electrospray ionization tandem mass spectrometry techniques. RESULTS: The detection of fluorescently labeled palmitic acid, even after 16 hours of incubation, was limited to approximately the outer 25% to 30% of the rat lens. Mass spectrometry also revealed the presence of free (13)C(18)-oleic acid in the cortex but not the nucleus. No evidence could be found for incorporation of fluorescently labeled palmitic acid into phospholipids; however, a low level of (13)C(18)-oleic acid incorporation into phosphatidylethanolamine (PE), specifically PE (PE 16:0/(13)C(18) 18:1) was detected in the lens cortex after 16 hours. CONCLUSIONS: These data demonstrate that uptake of exogenous (e.g., dietary fatty acids) by the lens and their incorporation into phospholipids is minimal, most likely occurring only during de novo synthesis in the outermost region of the lens. This finding adds support to the hypothesis that once synthesized there is no active remodeling or turnover of fiber cell phospholipids.

Ozone-induced dissociation on a modified tandem linear ion-trap: observations of different reactivity for isomeric lipids.

Ozone-induced dissociation (OzID) exploits the gas-phase reaction between mass-selected lipid ions and ozone vapor to determine the position(s) of unsaturation. In this contribution, we describe the modification of a tandem linear ion-trap mass spectrometer specifically for OzID analyses wherein ozone vapor is supplied to the collision cell. This instrumental configuration provides spatial separation between mass-selection, the ozonolysis reaction, and mass-analysis steps in the OzID process and thus delivers significant enhancements in speed and sensitivity (ca. 30-fold). These improvements allow spectra revealing the double-bond position(s) within unsaturated lipids to be acquired within 1 s: significantly enhancing the utility of OzID in high-throughput lipidomic protocols. The stable ozone concentration afforded by this modified instrument also allows direct comparison of relative reactivity of isomeric lipids and reveals reactivity trends related to (1) double-bond position, (2) substitution position on the glycerol backbone, and (3) stereochemistry. For cis- and trans-isomers, differences were also observed in the branching ratio of product ions arising from the gas-phase ozonolysis reaction, suggesting that relative ion abundances could be exploited as markers for double-bond geometry. Additional activation energy applied to mass-selected lipid ions during injection into the collision cell (with ozone present) was found to yield spectra containing both OzID and classical-CID fragment ions. This combination CID-OzID acquisition on an ostensibly simple monounsaturated phosphatidylcholine within a cow brain lipid extract provided evidence for up to four structurally distinct phospholipids differing in both double-bond position and sn-substitution.

Phospholipid composition of the rat lens is independent of diet.

Dietary fatty acids are known to influence the phospholipid composition of many tissues in the body, with lipid turnover occurring rapidly. The aim of this study was to investigate whether changes in the fatty acid composition of the diet can affect the phospholipid composition of the lens. Male Sprague-Dawley rats were fed three diets with distinct profiles in both essential and non-essential fatty acids. After 8 weeks, lenses and skeletal muscle were removed, and the lenses sectioned into nuclear and cortical regions. In these experiments, the lens cortex was synthesised during the course of the variable lipid diet. Phospholipids were then identified by electrospray ionisation tandem mass spectrometry, and quantified via the use of internal standards. The phospholipid compositions of the nuclear and cortical regions of the lens differed slightly between the two regions, but comparison of the equivalent regions across the diet groups showed remarkable similarity. In contrast, the phospholipid composition of skeletal muscle (medial gastrocnemius) in these rats varied significantly. This study provides the first direct evidence to show that the phospholipid composition of the lens is tightly regulated and thus appears to be independent of diet. As phospholipids determine membrane fluidity and influence the activity and function of integral membrane proteins, regulation of their composition may be important for the function of the lens.

Systematic differences in membrane acyl composition associated with varying body mass in mammals occur in all phospholipid classes: an analysis of kidney and brain.

The acyl composition of membrane phospholipids in kidney and brain of mammals of different body mass was examined. It was hypothesized that reduction in unsaturation index (number of double bonds per 100 acyl chains) of membrane phospholipids with increasing body mass in mammals would be made-up of similar changes in acyl composition across all phospholipid classes and that phospholipid class distribution would be regulated and similar in the same tissues of the different-sized mammals. The results of this study supported both hypotheses. Differences in membrane phospholipid acyl composition (i.e. decreased omega-3 fats, increased monounsaturated fats and decreased unsaturation index with increasing body size) were not restricted to any specific phospholipid molecule or to any specific phospholipid class but were observed in all phospholipid classes. With increase in body mass of mammals both monounsaturates and use of less unsaturated polyunsaturates increases at the expense of the long-chain highly unsaturated omega-3 and omega-6 polyunsaturates, producing decreases in membrane unsaturation. The distribution of membrane phospholipid classes was essentially the same in the different-sized mammals with phosphatidylcholine (PC) and phosphatidylethanolamine (PE) together constituting approximately 91% and approximately 88% of all phospholipids in kidney and brain, respectively. The lack of sphingomyelin in the mouse tissues and higher levels in larger mammals suggests an increased presence of membrane lipid rafts in larger mammals. The results of this study support the proposal that the physical properties of membranes are likely to be involved in changing metabolic rate.

Human lens lipids differ markedly from those of commonly used experimental animals.

Electrospray ionisation tandem mass spectrometry has allowed the unambiguous identification and quantification of individual lens phospholipids in human and six animal models. Using this approach ca. 100 unique phospholipids have been characterised. Parallel analysis of the same lens extracts by a novel direct-insertion electron-ionization technique found the cholesterol content of human lenses to be significantly higher (ca. 6 times) than lenses from the other animals. The most abundant phospholipids in all the lenses examined were choline-containing phospholipids. In rat, mouse, sheep, cow, pig and chicken, these were present largely as phosphatidylcholines, in contrast 66% of the total phospholipid in Homo sapiens was sphingomyelin, with the most abundant being dihydrosphingomyelins, in particular SM(d18:0/16:0) and SM(d18:0/24:1). The abundant glycerophospholipids within human lenses were found to be predominantly phosphatidylethanolamines and phosphatidylserines with surprisingly high concentrations of ether-linked alkyl chains identified in both classes. This study is the first to identify the phospholipid class (head-group) and assign the constituent fatty acid(s) for each lipid molecule and to quantify individual lens phospholipids using internal standards. These data clearly indicate marked differences in the membrane lipid composition of the human lens compared to commonly used animal models and thus predict a significant variation in the membrane properties of human lens fibre cells compared to those of other animals.

Ozone-induced dissociation: elucidation of double bond position within mass-selected lipid ions.

Ions formed from lipids during electrospray ionization of crude lipid extracts have been mass-selected within a quadrupole linear ion trap mass spectrometer and allowed to react with ozone vapor. Gas-phase ion-molecule reactions between unsaturated lipid ions and ozone are found to yield two primary product ions for each carbon-carbon double bond within the molecule. The mass-to-charge ratios of these chemically induced fragments are diagnostic of the position of unsaturation within the precursor ion. This novel analytical technique, dubbed ozone-induced dissociation (OzID), can be applied both in series and in parallel with conventional collision-induced dissociation (CID) to provide near-complete structural assignment of unknown lipids within complex mixtures without prior fractionation or derivatization. In this study, OzID is applied to a suite of complex lipid extracts from sources including human lens, bovine kidney, and commercial olive oil, thus demonstrating the technique to be applicable to a broad range of lipid classes including both neutral and acidic glycerophospholipids, sphingomyelins, and triacylglycerols. Gas-phase ozonolysis reactions are also observed with different types of precursor ions including [M+H]+, [M+Li]+, [M+Na]+, and [M-H]-: in each case yielding fragmentation data that allow double bond position to be unambiguously assigned. Within the human lens lipid extract, three sphingomyelin regioisomers, namely SM(d18:0/15Z-24:1), SM(d18:0/17Z-24:1), and SM(d18:0/19Z-24:1), and a novel phosphatidylethanolamine alkyl ether, GPEtn(11Z-18:1e/9Z-18:1), are identified using a combination of CID and OzID. These discoveries demonstrate that lipid identification based on CID alone belies the natural structural diversity in lipid biochemistry and illustrate the potential of OzID as a complementary approach within automated, high-throughput lipid analysis protocols.