Correction for tissue optical properties enables quantitative skin fluorescence measurements using multi-diameter single fiber reflectance spectroscopy.

BACKGROUND AND OBJECTIVE: Fluorescence measurements in the skin are very much affected by absorption and scattering but existing methods to correct for this are not applicable to superficial skin measurements. STUDY DESIGN/MATERIALS AND METHODS: The first use of multiple-diameter single fiber reflectance (MDSFR) and single fiber fluorescence (SFF) spectroscopy in human skin was investigated. MDSFR spectroscopy allows a quantification of the full optical properties in superficial skin (µa, µs' and γ), which can next be used to retrieve the corrected - intrinsic - fluorescence of a fluorophore Qµa,x(f). Our goal was to investigate the importance of such correction for individual patients. We studied this in 22 patients undergoing photodynamic therapy (PDT) for actinic keratosis. RESULTS: The magnitude of correction of fluorescence was around 4 (for both autofluorescence and protoporphyrin IX). Moreover, it was variable between patients, but also within patients over the course of fractionated aminolevulinic acid PDT (range 2.7-7.5). Patients also varied in the amount of protoporphyrin IX synthesis, photobleaching percentages and resynthesis (>100× difference between the lowest and highest PpIX synthesis). The autofluorescence was lower in actinic keratosis than contralateral normal skin (0.0032 versus 0.0052; P<0.0005). CONCLUSIONS: Our results clearly demonstrate the importance of correcting the measured fluorescence for optical properties, because these vary considerably between individual patients and also during PDT. Protoporphyrin IX synthesis and photobleaching kinetics allow monitoring clinical PDT which facilitates individual-based PDT dosing and improvement of clinical treatment protocols. Furthermore, the skin autofluorescence can be relevant for diagnostic use in the skin, but it may also be interesting because of its association with several internal diseases.

Extraction of intrinsic fluorescence from single fiber fluorescence measurements on a turbid medium: experimental validation.

The detailed mechanisms associated with the influence of scattering and absorption properties on the fluorescence intensity sampled by a single optical fiber have recently been elucidated based on Monte Carlo simulated data. Here we develop an experimental single fiber fluorescence (SFF) spectroscopy setup and validate the Monte Carlo data and semi-empirical model equation that describes the SFF signal as a function of scattering. We present a calibration procedure that corrects the SFF signal for all system-related, wavelength dependent transmission efficiencies to yield an absolute value of intrinsic fluorescence. The validity of the Monte Carlo data and semi-empirical model is demonstrated using a set of fluorescent phantoms with varying concentrations of Intralipid to vary the scattering properties, yielding a wide range of reduced scattering coefficients (µ's = 0-7 mm (-1)). We also introduce a small modification to the model to account for the case of µ's = 0 mm (-1) and show its relation to the experimental, simulated and theoretically calculated value of SFF intensity in the absence of scattering. Finally, we show that our method is also accurate in the presence of absorbers by performing measurements on phantoms containing red blood cells and correcting for their absorption properties.

Use of a coherent fiber bundle for multi-diameter single fiber reflectance spectroscopy.

Multi-diameter single fiber reflectance (MDSFR) spectroscopy enables quantitative measurement of tissue optical properties, including the reduced scattering coefficient and the phase function parameter γ. However, the accuracy and speed of the procedure are currently limited by the need for co-localized measurements using multiple fiber optic probes with different fiber diameters. This study demonstrates the use of a coherent fiber bundle acting as a single fiber with a variable diameter for the purposes of MDSFR spectroscopy. Using Intralipid optical phantoms with reduced scattering coefficients between 0.24 and 3 mm(-1), we find that the spectral reflectance and effective path lengths measured by the fiber bundle (NA = 0.40) are equivalent to those measured by single solid-core fibers (NA = 0.22) for fiber diameters between 0.4 and 1.0 mm (r ≥ 0.997). This one-to-one correlation may hold for a 0.2 mm fiber diameter as well (r = 0.816); however, the experimental system used in this study suffers from a low signal-to-noise for small dimensionless reduced scattering coefficients due to spurious back reflections within the experimental system. Based on these results, the coherent fiber bundle is suitable for use as a variable-diameter fiber in clinical MDSFR quantification of tissue optical properties.

Randomized controlled trial of intubation with the McGrath Series 5 videolaryngoscope by inexperienced anaesthetists.

BACKGROUND: The McGrath Series 5 videolaryngoscope might reduce the incidence of unexpected difficult tracheal intubation. If it also performs as well as a standard laryngoscope during uncomplicated intubations, there would be an argument for the McGrath to become the laryngoscope of choice in higher risk settings, such as rapid sequence induction by inexperienced anaesthetists. Therefore, we compared the McGrath and the Macintosh laryngoscopes during routine tracheal intubation performed by inexperienced anaesthetists. METHODS: Single-blind randomized controlled trial with 120 adult patients allocated to intubation by first-year anaesthetic trainees, using a McGrath or Macintosh laryngoscope. The primary outcome was time to intubation. Secondary outcomes were quality of view at laryngoscopy and evidence of differential learning between using the two laryngoscopes. A Cox proportional hazards model was used to determine the effect of the laryngoscopes on time to intubation. RESULTS: Duration of intubation was significantly longer (P<0.001) in the McGrath group [median (IQR); 47.0 (39.0-60.0) vs 29.5 (23.0-36.8) s]. There were no significant differences in other outcomes, including grade of laryngoscopy view, visual confirmation of tube placement, number of laryngoscopies, or complications (oesophageal intubation, hypoxaemia, and airway trauma). There was no differential learning effect. CONCLUSIONS: There were no advantages to using the McGrath laryngoscope for uncomplicated tracheal intubation and duration of intubation was longer, so it should not be used as a first-line laryngoscope instrument by inexperienced anaesthetists.

Sex and muscle structural lipids in obese subjects - an impact on insulin action?

BACKGROUND: Long-chain polyunsaturated fatty acid (LCPUFA) especially the n-3-FA of skeletal muscle phospholipids may facilitate insulin action, whereas saturated and trans-FA act oppositely. Community studies show that non-diabetic weight matched obese men and women display similar insulin resistance, despite the fact that an android fat distribution is detrimental to insulin action. The increased extramyocellular fat mass of obese women may act in a paracrine manner such that its release of free FA and cytokines may hamper in situ desaturation and elongation of FA in skeletal muscle phospholipids. MATERIAL AND METHODS: To test the hypothesis that obese women may display an inferior FA composition compared to obese men, the FA composition of skeletal muscle phospholipids was determined in vastus lateralis biopsies obtained from 12 non-diabetic obese women with a typical gynoid fat distribution, nine non-diabetic obese men with a typical android fat distribution and 12 (seven females) lean age matched healthy controls (body mass index 34.6 +/- 1.0 kg m(-2), 36.5 +/- 1.2 and 22.5 +/- 0.5; age 47 +/- 2 years, 51 +/- 3 and 49 +/- 2). RESULTS: Obese women displayed decreased LCPUFA n-3 and ratio of n-3/n-6 PUFA, whereas trans-FA and palmitic-FA (C16 : 0) were increased compared to obese men and controls (all Ps < 0.05). Plasma high-density lipoprotein cholesterol (HDL-C), triglycerides and a marker of insulin sensitivity were similar between obese women and men but impaired compared to controls (Ps < 0.05). CONCLUSIONS: The data support the hypothesis that insulin resistant non-diabetic obese men display a more optimal skeletal muscle phospholipid FA composition than their female counterparts, which may be a mechanism to compensate the detrimental effect on insulin action of an android fat distribution.

Effects of increasing dietary concentrations of specific structured triacylglycerides on performance and nitrogen and energy metabolism in broiler chickens.

Specific structured triacylglycerides (STG) containing medium chain fatty acids in sn-1,3 positions and a long chain fatty acid in sn-2 position were prepared from rapeseed oil and capric acid (C10:0). A total of 80 female broiler chickens (Ross 208) were randomly allocated into five dietary treatments as two series of 40 chicks: a basal diet with graded levels of STG of 0, 20, 40, 60 and 80 g/kg diet at the expense of rapeseed oil were fed to the chickens in groups of four. At 12 d of age the chickens were placed pair-wise in metabolism cages. The grower period (d 13-36) was divided into four consecutive balance periods each of 6 d. Two 24 h measurements of gas exchange in two open-air circuit respiration chambers were performed during the second and third day of each balance period. During the whole experiment there was a negative effect of the inclusion of STG on average feed intake. However, this only slightly affected average daily weight gain. Feed conversion efficiency improved linearly with the inclusion level of STG. Daily gain adjusted to mean daily feed intake increased linearly with inclusion rate of STG, indicating that the weight gain was affected by both feed intake and the enhancing effect on digestibility of STG. Weight of small intestine and colon decreased with increasing inclusion of STG. Utilisation of dietary protein relative to intake increased while that of retained fat tended to decrease resulting in a decreased utilisation of metabolisable energy (RE/ME) in birds receiving STG. Heat production (HE) was slightly lower in the STG groups. More of the dietary fat was oxidised when more STG was added, although the total amount of fat in the diets was kept constant.

Dietary structured lipids for post-weaning piglets: fat digestibility, nitrogen retention and fatty acid profiles of tissues.

In four groups of post-weaning piglets the effects of triacylglycerol structure and fatty acid profiles of four dietary fats on apparent faecal nutrient digestibility, nitrogen retention and fatty acid profiles of platelet and erythrocyte membranes, liver, adipose tissue and skeletal muscle were examined. Dietary fats included as 10% (w/w) of the diets were two structured fats of rapeseed oil interesterified with tridecanoin (R1) or coconut oil (R2), respectively, one mixture of rapeseed oil and coconut oil (R3) and rapeseed oil as control (R4). Faeces and urine from piglets weaned at 28 days of age were collected quantitatively during three periods each of 5 days, in which the piglets were kept in metabolism cages for measurement of apparent faecal nutrient and energy digestibility and nitrogen retention. Apparent faecal fat digestibilities were significantly improved in groups fed interesterified fats or the physical mixtures (R1, R2 and R3) compared with rapeseed oil (R4). Apparent faecal nitrogen digestibility and retention were similar in all four groups in the three periods, but increased with time. Apparent faecal fat digestibilities were significantly improved from the first to the third week in the groups R1 and R2. Fatty acid profiles in platelet and erythrocyte membranes and in tissues reflected the fatty acid profile of the dietary fat, except for medium-chain fatty acids, which were only found in low proportions, indicating that 10:0 was mainly used as an energy source.

Natural experiments: an underused tool for public health?

Policymakers and public health researchers alike have demanded better evidence of the effects of interventions on health inequalities. These calls have been repeated most recently in the UK in the final Wanless report, which spoke of the "almost complete lack of an evidence base on the cost-effectiveness of public health interventions", and pointed more generally to the limited evidence base for public health policy and practice. Wanless and others have suggested that the gaps may be partially filled by exploiting the opportunities offered by "natural experiments", such as changes in employment opportunities, housing provision, or cigarette pricing. Natural experiments have an important contributions to make within the health inequalities agenda. First, they can play an important role in investigating the determinants of health inequalities. Second, they can assist in the identification of effective interventions, an area where it is widely acknowledged that the evidence-base is currently sparsely populated. This paper discusses some of the benefits and limitations of using this type of evidence, drawing on two ongoing quasi-experimental studies as examples.

Synthesis of structured triacylglycerols containing caproic acid by lipase-catalyzed acidolysis: optimization by response surface methodology.

Production in a batch reactor with a solvent-free system of structured triacylglycerols containing short-chain fatty acids by Lipozyme RM IM-catalyzed acidolysis between rapeseed oil and caproic acid was optimized using response surface methodology (RSM). Reaction time (t(r)), substrate ratio (S(r)), enzyme load (E(l), based on substrate), water content (W(c), based on enzyme), and reaction temperature (T(e)), the five most important parameters for the reaction, were chosen for the optimization. The range of each parameter was selected as follows: t(r) = 5-17 h; E(l) = 6-14 wt %; T(e) = 45-65 degrees C; S(r) = 2-6 mol/mol; and W(c) = 2-12 wt %. The biocatalyst was Lipozyme RM IM, in which Rhizomucor miehei lipase is immobilized on a resin. The incorporation of caproic acid into rapeseed oil was the main monitoring response. In addition, the contents of mono-incorporated structured triacylglycerols and di-incorporated structured triacylglycerols were also evaluated. The optimal reaction conditions for the incorporation of caproic acid and the content of di-incorporated structured triacylglycerols were as follows: t(r) = 17 h; S(r) = 5; E(l) = 14 wt %; W(c) = 10 wt %; T(e) = 65 degrees C. At these conditions, products with 55 mol % incorporation of caproic acid and 55 mol % di-incorporated structured triacylglycerols were obtained.

Comparison of total oral bioavailability and the lymphatic transport of halofantrine from three different unsaturated triglycerides in lymph-cannulated conscious rats.

The lymphatic transport and the portal absorption of the lipophilic drug halofantrine were investigated in a conscious rat model. The rats were dosed with 0.1 g with triolein, trilinolein or trilinolenin containing 2 mg halofantrine. Following oral administration of the triglycerides, the mesenteric lymph and plasma samples were collected. The lymphatic transport for halofantrine was 11.1+/-1.2 after administration of trilinolein, 9.0+/-3.5 for trilinolenin and 8.6+/-2.2 for triolein and the total amount of halofantrine transported in the lymph was linear proportional with the amount of triglyceride in the lymph. The absorption of halofantrine directly into the blood showed a trend towards a higher AUC for trilinolien and trilinolenin compared to triolein, but no statistical difference could be found. The statistically analysis of the mean total bioavailability therefore shows that the absorption of halofantrine was largely independent on triglyceride unsaturation.

Adolescents in China.

This paper reviews the nature and explores the context of, and reactions to, reproductive health education in China by both the target population of adolescents at school and the wider public. The debate about reproductive health education and its content is taking place within the context of rapid behavioural and sociological changes in China which, in turn is, generating conflicting demands concerning the need for education by the population and the control of the population by the government. Foucault's theories on sexuality and discipline are found to be useful in exploring the subject of reproductive health education in China.

Lymphatic transport of fat in rats with normal- and malabsorption following intake of fats made from fish oil and decanoic acid. Effects of triacylglycerol structure.

Fish oils contain essential polyunsaturated fatty acids of the n-3 family. In fat malabsorption the n-3 fatty acids are poorly absorbed. Absorption may be improved by modifying the fatty acid profile of fish oil through interesterification with medium chain fatty acids. We examined the absorption of fish oil interesterified with decanoic acid in rats with normal- and malabsorption compared to a physical mixture and the fish oil itself. The interesterified fats were: 1) a regiospecific fat with decanoic acid located mainly in the sn1/3-positions and a long chain fatty acid from fish oil in the sn2-position, 2) a fat with a random distribution of fatty acids in all positions of the triacylglycerol. The main mesenteric lymph duct was cannulated for collection of lymph. In the malabsorbing rats the common bile duct was cannulated as well to divert both pancreatic juice and bile. The fatty acid composition in lymph samples collected for 24 hours was determined. Accumulated transport of n-3 fatty acids from fish oil was improved in malabsorbing rats and recoveries of fatty acids after 24 hours were improved in both rats with normal- and malabsorption administered the randomized fat compared to fish oil.

Intestinal absorption of specific structured triacylglycerols.

To clarify the intestinal absorption pathway of medium-chain fatty acids from MLM-type structured triacylglycerols containing both medium- and long-chain fatty acids, we studied the lymphatic transport of 1,3-dioctanoyl-2-linoleoyl-sn-glycerol (8:0/18:2/8:0), 1,3-didecanoyl-2-linoleoyl-sn-glycerol (10:0/18:2/10:0), and 1,3-didodecanoyl-2-linoleoyl-sn-glycerol (12:0/18:2/12:0) in a rat model. Safflower oil was used in the absorption study in order to compare the absorption of medium-chain fatty acids and long-chain fatty acids. The triacylglycerol species of lymph lipids were separated on a reversed-phase high performance liquid chromatograph (RP-HPLC) and identified by atmospheric pressure chemical ionization mass spectrometry. The composition of triacylglycerols was quantified by RP-HPLC with evaporative light scattering detection. The intact MLM-type triacylglycerols were detected in the lymph lipids after administration of the specific structured triacylglycerols (STAG). The recoveries of 8:0/18:2/8:0, 10:0/18:2/10:0, and 12:0/18:2/12:0 were 0.6%, 12%, and 5%, respectively. Several new triacylglycerol species were detected in the lymph lipids, including MLL-, LLL-, and MMM-type triacylglycerols. From the present study we conclude that the medium-chain fatty acids from STAG, in addition to absorption into the portal blood as free fatty acids, are absorbed by the same pathway as the conventional long-chain triacylglycerols, that is, they are hydrolyzed into free fatty acids, absorbed and activated into CoA, and reacylated into triacylglycerols in the enterocyte. The hydrolysis of MLM-type STAG is predominantly partial hydrolysis, whereas part of the STAG can also be hydrolyzed to free glycerol and free fatty acids.

Effect of high-dose growth hormone and glutamine on body composition, urine creatinine excretion, fatty acid absorption, and essential fatty acids status in short bowel patients: a randomized, double-blind, crossover, placebo-controlled study.

BACKGROUND: Positive effects of high dose growth hormone and glutamine (GH + GLN) on body composition in short bowel patients have been described. Lack of effects on intestinal absorption found in some studies has been ascribed to concomitant essential fatty acid (EFA) deficiency. This study describes changes in body weight (BW) and composition, 24-h urine creatinine excretion, intestinal fatty acid absorption (total, saturated, unsaturated and EFA), and EFA status in relation to treatment with GH + GLN in 8 short bowel patients. METHODS: A double-blind, crossover study between placebo and growth hormone (mean, 0.12 mg/kg/day) plus oral (mean, 28 g/day) and parenteral glutamine (mean, 5.2 g/day) for 28 days. Body composition was measured by dual-energy absorptiometry (DEXA) scans. Intestinal fatty acid absorption was evaluated in balance studies, and EFAs were measured in plasma phospholipids by gas liquid chromatography. RESULTS: Active treatment did not increase BW, lean body mass (LBM), fat mass (FM) and bone mass significantly compared with placebo treatment, but BW increased 1.03 kg (1.7%, P < 0.05), LBM 2.93 kg (8.7%, P < 0.001) and FM decreased 2.41 kg (10.6%, P < 0.001) in comparison with baseline. Twenty-four-hour urine creatinine excretion did not differ between study periods. No changes in intestinal absorption of fatty acids were seen, and no changes in EFAs measured in plasma phospholipids were observed. Only 1 of 8 patients, who did not receive parenteral lipids, had a Holman index above 0.2, indicative of EFA deficiency. All developed peripheral oedema. CONCLUSIONS: Combined high dose growth hormone and glutamine administered for 4 weeks, did not improve absorption of fatty acids or EFA status in short bowel patients. No changes in BW or composition were seen when comparing treatment to placebo periods. The increase in LBM measured by DEXA scan, comparing treatment and baseline periods, was not accompanied by an increase in the 24-h urinary creatinine excretion and is suspected to be associated with an accumulation in extracellular fluids.

Regioisomers of octanoic acid-containing structured triacylglycerols analyzed by tandem mass spectrometry using ammonia negative ion chemical ionization.

Tandem mass spectrometry based on ammonia negative ion chemical ionization and sample introduction via direct exposure probe was applied to analysis of regioisomeric structures of octanoic acid containing structured triacylglycerols (TAG) of type MML, MLM, MLL, and LML (M, medium-chain fatty acid; L, long-chain fatty acid). Collision-induced dissociation of deprotonated parent TAG with argon was used to produce daughter ion spectra with appropriate fragmentation patterns for structure determination. Fatty acids constituting the TAG molecule were identified according to [RCO2]- ions in the daughter ion spectra. With the standard curve for ratios of [M-H-RCO2H-100]- ions corresponding to each [RCO2]- ion, determined with known mixtures of sn-1/3 and sn-2 regioisomers of structured TAG, it was possible to determine the proportions of different regioisomers in unknown samples. The method enabled quantification of MML- and MLM-type structured TAG. In the case of MLL- and LML-type TAG, it was possible to determine the most abundant regioisomer in the unknown mixture and estimate the proportions of regioisomers when there were more than 50% MLL-type isomers in the mixture.

Splanchnic metabolism of fuel substrates in acute liver failure.

BACKGROUND/AIMS: This study aimed to characterize the exchange of fuel substrates in the splanchnic circulation in acute liver failure. METHODS: Liver vein catheterization was used in 22 patients with acute liver failure after development of hepatic encephalopathy grade III-IV Healthy controls, patients with cirrhosis and patients with acute on chronic liver disease were also studied. RESULTS: In acute liver failure there was splanchnic removal of glucose (0.21+/-0.44 mmol/min), release of lactate (0.34+/-0.37 mmol/min), pyruvate (0.08+/-0.06 mmol/min) and ketone bodies (0.04+/-0.02 mmol/min), while extraction of amino acids and free fatty acids was insignificant. In the acute liver failure group, a normal hepatic venous oxygen saturation (0.69+/-0.12) and normal pyruvate/lactate ratio suggested absence of hypoxia even though the acetoacetate/beta-hydroxybutyrate ratio was decreased. Only in the acute liver failure group did the measured splanchnic oxygen content difference exceed what could be accounted for even by hypothesizing complete oxidation of all extracted blood-borne fuel substrates; oxidation of endogenous substrates may be quantitatively important in this condition. CONCLUSION: Acute liver failure was associated with a state of accelerated glycolysis in the splanchnic region, leading to release of lactate in the absence of splanchnic hypoxia.

Absorption by rats of tocopherols present in edible vegetable oils.

The absorption of tocopherols (alpha, gamma, and delta) and fatty acids from rapeseed (RO), soybean (SOO), and sunflower (SUO) oil, both from the natural oils and from the oils following moderate heating (180 degrees C for 15 min), was measured in lymph-cannulated rats. Oils were administered as emulsions through a gastrostomy tube, and lymph samples were collected for 24 h. The composition of tocopherols in oils and lymph fractions was measured by high-performance liquid chromatography, and fatty acids were measured by gas-liquid chromatography. The highest accumulated transport of alpha-tocopherol was observed after SUO administration, the lowest after SOO, with RO in between, corresponding to their relative contents (41.6 +/- 8.8, 32.7 +/- 5.0, and 24.9 +/- 4.3 microg at 24 h after administration of SUO, RO, and SOO, respectively). The calculated recoveries (in %) 24 h after oil administration were 21.4 +/- 4.5, 45.7 +/- 7.0, and 78.8 +/- 13.5 for SUO, RO, and SOO, respectively, suggesting that the absorption efficiency decreased when the alpha-tocopherol concentration increased. The recovery of alpha-tocopherol was higher than the recoveries of gamma- and delta-tocopherol, indicating that the different tocopherols were not absorbed to the same extent or with similar rates. No differences between unheated and heated oils were observed in the absorption of tocopherols, whereas heating led to lower absorption of fatty acids, thus showing no direct association between absorption of tocopherols and fatty acids.