Age-related changes of the dentate nuclei in normal adults as revealed by 3D fast low angle shot (FLASH) echo sequence magnetic resonance imaging

The aim of the present study was to investigate age-related changes in iron-deposition in dentate nuclei using iron-induced susceptibility effects in magnetic resonance imaging. MR images from 74 healthy subjects (age range 20-68 years) were obtained using a three-dimensional (3D) T1-weighted fast low angle shot (FLASH) echo sequence. Signal intensities of the dentate nuclei and cerebellar white matter were bilaterally measured independently by three blinded investigators. The signal intensities of dentate nuclei were intraindividually normalised to the corresponding signal intensities of the cerebellar white matter of corresponding slices. Mean normalised signal intensities were correlated with age and compared between different age decades and gender. Intraclass correlation coefficients were high (dentate nuclei: 0.98, cerebellar white matter: 0.75) indicating sufficient interrater reliabilities for the determination of signal intensities. Bland-Altman analysis confirmed this finding. The normalised mean signal intensity of the dentate nuclei correlated inversely with age (r = -0.462, p < 0.0001). Comparison of age decades revealed that significant decreases took place between the third and fourth decade and to a lesser degree between the fourth and fifth decade. Moreover, variability of normalised mean signal intensities of the dentate nuclei increased significantly with age (r = 0.964, p = 0.008). There were no differences of the normalised mean signal intensities between genders. The present study revealed an age-dependent decrease of signal intensities in dentate nuclei most likely reflecting an age-dependent increase in dentate iron concentration. These age-dependent changes have to be taken into account in interpretation of disease related MR changes of cerebellar nuclei in patients with degenerative or acquired cerebellar ataxia.

Parameters with influence on the droplet size of w/o emulsions

The aim of this study was to show that for w/o emulsions a modulation of components and parameters is necessary. Therefore several w/o emulsions were produced according to a 2(4) factorial design to get the information that pressure and temperature as production parameter have less influence on the droplet size than the substance components olive oil and lecithin. Furthermore an interaction between surfactant and oil component was observed which resulted in an increase of droplet size. With the following experiments the interfacial tension and the viscosity as physicochemical parameters were determined but gave no explanation for the phenomenon of an increasing droplet size if olive oil and lecithin are part of the formulation. So the influence of substance components was examined in more detail with the successive addition of oleic acid or oleyl alcohol to MCT and due to this the presence of unsaturated substances in olive oil could be determined as a possible reason for interactions with lecithin.

Neuropsychological Deficits and Concomitant Clinical Symptoms in Schizophrenia

The most frequently reported neuropsychological deficits in schizophrenia are those of attention, executive function, and verbal memory. Whereas the former appear to be related to negative symptoms of schizophrenia, there is little agreement about which clinical symptoms are related to the verbal memory deficit. The aim of the present study was to delineate further the pattern of neuropsychological deficits in schizophrenia—especially those of verbal memory—and their relationship to clinical symptoms. One hundred patients with chronic schizophrenia and 62 healthy control subjects took part in the study. Assessments of patients took place within the first 3 weeks after admission to hospital. Nine neuropsychological tests, mainly measuring executive and memory function and attention, were administered to all subjects, and clinical symptoms, such as psychotic and negative symptoms and conceptual disorganization, were assessed in patients by means of the Positive and Negative Syndrome Scale (PANSS). Patients showed widespread cognitive deficits with verbal memory impairment best discriminating patients and controls. Conceptual disorganization was partly accounted for by poor verbal memory and a low IQ estimate, and negative symptoms by deficient word fluency; positive symptoms were not significantly related to cognitive deficits. The results indicate that there is a specific relationship between neuropsychological deficits and the more chronic of the clinical symptoms.

Sparse imaging of the auditory oddball task with functional MRI

Cortical reactions to rare task-related stimuli have been studied with electrophysiological methods in the assessment of the P300 component as well as in functional imaging studies with regard to oddball tasks. While functional magnetic resonance imaging studies using auditory stimuli have to deal with interference between auditory stimuli and scanner noise, the aim of our study was to assess auditory target processing with the sparse imaging method. Single volumes of echo-planar imaging were acquired 4 s following the onset of the stimuli of interest. In keeping with previous studies, target stimuli activated the insula, superior temporal gyrus, cingulate gyrus, middle frontal gyrus, parietal cortex and the cerebellum. Our results encourage the application of the sparse imaging method in experiments on cognitive processing elicited by auditory stimulation in a silent environment.

Treatment of acute alcohol withdrawal with gabapentin: results from a controlled two-center trial

A few case reports and data from animal experiments point to a possible efficacy of gabapentin (GP) in the treatment of alcohol withdrawal syndrome (AWS). Because of ethical considerations, the efficacy of GP in acute AWS was tested in an add-on fashion to clomethiazole (CLO). Given that the symptom-triggered amount of CLO required to limit AWS within the first 24 hours is related to the severity of AWS, we tested this amount of CLO during placebo (P) or GP (400 mg qid) under double blind, randomized conditions. Sixty-one patients (P = 29/GP = 32) suffering from alcohol dependence (ICD-10) and without any other psychiatric condition or psychotropic medication were included. The groups were not significantly different in baseline characteristics (eg, demographic data, severity of AWS). Both ITT and completer analyses revealed no significant differences between the groups considering the primary effectiveness measure: amount of CLO required in the first 24 hours (P = 6.1 +/- 5.4/GP = 6.2 +/- 4.7 capsules). In addition, premature discontinuations (P = 3/GP = 2) and decreases in Mainz Alcohol Withdrawal Scores were not significantly different in the first 48 hours of AWS (secondary effectiveness measures). Tolerability of combined CLO/GP was studied throughout the whole treatment comprising a 5-day lasting reduction part subsequent to the first 48 hours. Throughout the whole 7-day treatment a total of 5 and 2 patients dropped out and 6 and 5 patients reported adverse clinical events in the P and GP groups, respectively. All together, GP (400 mg qid) was no better than P in saving initial consumption of CLO or decreasing initial Mainz Alcohol Withdrawal Scores suggesting that GP was ineffective in the management of acute AWS in this model. The combination of GP and CLO was safe.

Lyoprotection of aviscumine with low molecular weight dextrans

The aim of this research was to ascertain whether dextrans with low molecular weight will stabilize aviscumine. During freeze-drying increasing concentrations of dextran T1 (MW 1000) stabilized aviscumine. Eight percent of dextran resulted in a nearly 100% recovery of the activity and in addition a complete amorphous structure of the solid phase was obtained. By decreasing the molecular weight of the dextran from 75 to 1 kDa, the protein activity was increased by 20% in the lyophilisate. Combinations of dextran with either trehalose or mannitol showed no additional effects on stability. The improved stabilization of aviscumine using low molecular weight dextrans is explained by an increased interaction between the protein and the dextran molecules (like hydrogen bonds), whereas they are sterically hindered if larger dextran molecules are used. When the protein concentration was increased from 10 to 100 microg/ml (in formulas with 8% dextran T1), no influence on the protein activity could be found. With regard to the carbohydrate-binding activity of the protein, it was shown that the optimal content of residual water in the lyophilisate should be about 2%. Above and below this percentage a destabilization of the protein was observed. The often discussed failure of dextran as a stabilizing excipient in the freeze-drying of proteins seems to be a question of the selection of the correct molecular weight.

Complex formation of sericoside with hydrophilic cyclodextrins: improvement of solubility and skin penetration in topical emulsion based formulations

The main objective of this study was to devise novel methods for improving the solubility of the anti-inflammatory triterpenoid sericoside, the main component of Terminalia sericea extract, thus enabling its incorporation into topical formulations. Sericoside was stabilized by complex formation with hydrophilic derivatives of beta- and gamma-cyclodextrins in a molar ratio of 1.0:1.1. The complex of extract and cyclodextrin was equilibrated in water at 25 degrees C for approximately 24 h. The dehydrated complexes of T. sericea extract and cyclodextrin were characterized by differential scanning calorimetry, thermogravimetry analysis and X-ray diffraction. Complex formation with beta-cyclodextrin as well as gamma-cyclodextrin derivatives was detectable using these three analytical tools; however, only complexes with gamma-cyclodextrin derivatives showed stability upon storage after incorporation into topical o/w or w/o formulations. Furthermore, a T. sericea extract/gamma-cyclodextrin complex incorporated in an o/w formulation resulted in a 2.6-fold higher percutaneous penetration of sericoside in in vitro excised pig skin as compared to pure T. sericea extract. For the first time, the virtually insoluble anti-inflammatory active sericoside was incorporated into a topical emulsion based formulation in a stable manner, resulting in efficient skin penetration.

Mismatch negativity results from bilateral asymmetric dipole sources in the frontal and temporal lobes

The event-related potential (ERP) reflecting auditory change detection (mismatch negativity, MMN) registers automatic selective processing of a deviant sound with respect to a working memory template resulting from a series of standard sounds. Controversy remains whether MMN can be generated in the frontal as well as the temporal cortex. Our aim was to see if frontal as well as temporal lobe dipoles could explain MMN recorded after pitch-deviants (Pd-MMN) and duration deviants (Dd-MMN). EEG recordings were taken from 32 sites in 14 healthy subjects during a passive 3-tone oddball presented during a simple visual discrimination and an active auditory discrimination condition. Both conditions were repeated after one month. The Pd-MMN was larger, peaked earlier and correlated better between sessions than the Dd-MMN. Two dipoles in the auditory cortex and two in the frontal lobe (left cingulate and right inferior frontal cortex) were found to be similarly placed for Pd- and Dd-MMN, and were well replicated on retest. This study confirms interactions between activity generated in the frontal and auditory temporal cortices in automatic attention-like processes that resemble initial brain imaging reports of unconscious visual change detection. The lack of interference between sessions shows that the situation is likely to be sensitive to treatment or illness effects on fronto-temporal interactions involving repeated measures.

Properties of ibuprofen crystallized under various conditions: a comparative study

Different crystal forms of the analgesic drug ibuprofen were prepared and characterized in this study. Various conditions were used for the crystallization: crystallization was carried out using the solvent change method, the temperature change method, and the solvent evaporation method. Crystals were grown from different solvents. Different crystal forms with different properties were observed: cubic, needle-shaped, and plate-shaped crystals were obtained. Spherical agglomeration occurs when crystallization is carried out in acetonitrile or methanol. Flowability of these spherical crystals is increased. All crystals were determined as isomorphic by differential scanning calorimetry and x-ray analysis--which queries doubtful results of recent publications. Properties like dissolution behavior and properties influencing the manufacturing of dosage forms--like flowability--differ. Thus the choice of the optimal preparation method influencing the crystal habit is important in manufacturing the drug ibuprofen.

Formulating and stability of benzodiazepines in a new lipid emulsion formulation

The objective of the current study was to evaluate the novelty of a new lipid emulsion formulation containing 30% oil phase as a drug delivery system. Therefore different benzodiazepines (BZs), namely diazepam, tetrazepam, clonazepam and lorazepam, were incorporated into this emulsion formulation. This lipid emulsion formulation showed enhanced solubilization capacity as 10 mg/ml, 10 mg/ml, 0.9 mg/ml, and 1.8 mg/ml formulations for diazepam, tetrazepam, clonazepam, and lorazepam were achieved, respectively. Incorporating the drugs into the lipid emulsion did not alter its physicochemical properties. Also the free and the drug emulsion formulations displayed good physical stability after autoclaving and after around one year of storage at shelf, as no changes in the physicochemical properties were observed. Most drugs also showed stable behavior after autoclaving and after approximately 1 year of storage at shelf. The only exception was lorazepam, as only around 50% of the drug was still intact after autoclaving.

Properties of ibuprofen crystallized under various conditions: a comparative study

Different crystal forms of the analgesic drug ibuprofen were prepared and characterized in this study. Various conditions were used for the crystallization: crystallization was carried out using the solvent change method, the temperature change method, and the solvent evaporation method. Crystals were grown from different solvents. Different crystal forms with different properties were observed: cubic, needle-shaped, and plate-shaped crystals were obtained. Spherical agglomeration occurs when crystallization is carried out in acetonitrile or methanol. Flowability of these spherical crystals is increased. All crystals were determined as isomorphic by differential scanning calorimetry and x-ray analysis--which queries doubtful results of recent publications. Properties like dissolution behavior and properties influencing the manufacturing of dosage forms--like flowability--differ. Thus the choice of the optimal preparation method influencing the crystal habit is important in manufacturing the drug ibuprofen.

Cortical activation to auditory mismatch elicited by frequency deviant and complex novel sounds: a PET study

The analysis of auditory deviant events outside the focus of attention is a fundamental capacity of human information processing and has been studied in experiments on Mismatch Negativity (MMN) and the P3a component in evoked potential research. However, generators contributing to these components are still under discussion. Here we assessed cortical blood flow to auditory stimulation in three conditions. Six healthy subjects were presented with standard tones, frequency deviant tones (MMN condition), and complex novel sounds (Novelty condition), while attention was directed to a nondemanding visual task. Analysis of the MMN condition contrasted with thestandard condition revealed blood flow changes in the left and right superior temporal gyrus, right superior temporal sulcus and left inferior frontal gyrus. Complex novel sounds contrasted with the standard condition activated the left superior temporal gyrus and the left inferior and middle frontal gyrus. A small subcortical activation emerged in the left parahippocampal gyrus and an extended activation was found covering the right superior temporal gyrus. Novel sounds activated the right inferior frontal gyrus when controlling for deviance probability. In contrast to previous studies our results indicate a left hemisphere contribution to a frontotemporal network of auditory deviance processing. Our results provide further evidence for a contribution of the frontal cortex to the processing of auditory deviance outside the focus of directed attention.

Jet milling--a new technique for microparticle preparation

An innovative technique for solvent free preparation of microparticles is described. Microparticles were prepared by a melt grinding technique which consists of three consecutive steps of melting in case of placebo microparticles or co-melting of polymer and drug in case of drug loaded microparticles, respectively, and pregrinding. In a final jet milling step the reduction of the particle size and smoothening of the microparticle surface occurred. Different polymers of PLA and PLGA type were utilised. The influence of the preparation parameters during the process were investigated according to microparticle properties like particle size distribution, habitus or surface morphology by executing a 2((5-2)) factorial design. The minimum mean particle size distribution (x(50) value) reached 4-6 microm. Scanning electron microscopy revealed that non-porous microparticles with a smooth surface were prepared. The release pattern of estrioltriacetate loaded microparticles of Resomer 202H nearly followed a zero order release kinetic over a period of 21 days without an initial burst effect. The preparation process can be carried out in a reproducible manner. The results demonstrate that microparticle preparation is possible by the following unique melt grinding technique without using organic solvents.

Modulation of mismatch negativity by stimulus deviance and modality of attention

We studied the effect of attention on the processing of auditory sensory inputs by means of the mismatch negativity (MMN) potential, which can be derived from event-related EEG. A series of frequent standard and rare deviant auditory stimuli were presented to 20 healthy subjects in two recording sessions about five weeks apart. Deviant stimuli were either low or highly deviant as compared to the standard stimulus. While MMN was recorded, subjects were performing a visual and, subsequently, an auditory discrimination task. Directing attention towards the auditory task was associated with increased MMN amplitude only in response to low deviant stimuli and only in the first recording session. No change of MMN amplitude was found when directing attention towards the visual task or when MMN was recorded in response to highly deviant auditory stimuli. The latter may trigger an involuntary switch of attention, thereby overwriting the effect of task-directed attention. Conversely, the effects of attention on the processing of low deviant stimuli appear to be fragile and diminish with increasing automaticity of task execution.

The movement-related potential in children with migraine and tension-type headache

Migraine is characterized by an elevated contingent negative variation (CNV) in adults and children. In the present study the movement-related potential preceding self-initiated movements, the Bereitschaftspotential, was investigated in 30 children (mean age 12 years) who were suffering from migraine and tension-type headache and in 16 healthy age-matched controls. Children pressed a button 80 times with the right index finger while movement-related potentials were recorded from frontal and central electrodes. Whereas healthy children evidenced positive movement-related potentials at left and midline positions, children with migraine and tension-type headache showed negative movement-related potentials at midline leads without lateralization. Negativity was even more pronounced in cases of migraine with than without aura symptoms.

Event- and Motor-Related Potentials During the Continuous Performance Task in Attention- Deficit/Hyperactivity Disorder

Abstract Contingent negative variation (CNV) and evoked potentials were recorded during the continuous performance test in 20 children (aged 7 to 12) with attention deficit/hyperactivity disorder (ADHD) and in 19 age-matched healthy children. A series of letters were displayed every 2.1 s and a button had to be pressed whenever the letter O was followed by an X. Children were also given neuropsychological tests and questionnaires assessing anxiety and depression. Unlike ADHD children, healthy children showed a more pronounced CNV after the cue - the letter O - than after the distractors. At Fz, CNV negativity was significantly correlated with IQ and executive function. Control children also exhibited a higher parietal N375 post S1 - likely to be associated with letter processing - and a higher N550 amplitude at Fz than ADHD children post S1 and S2; both groups showed a higher N550 amplitude whenever X followed non-O or O was followed by non-X. This component appears to be involved in decision-making processes regarding the initiation or inhibition of movement. ADHD children had a faster reaction time but made more errors of omission and commission. Results suggest that ADHD children show deficits in both stimulus processing and response execution.

Development of a novel parenteral formulation for tetrazepam using a lipid emulsion

A novel parenteral formulation for tetrazepam (10 mg/ml) was developed using lipid emulsions. This formulation utilized a new lipid emulsion formulation, which was developed by changing the polarity of the oil phase. It was found that increasing the polarity of the oil phase resulted in enhanced solubility of tetrazepam. Tetrazepam showed higher solubility in a mixture of castor oil and middle-chain triglycerides (MCTs) (1:1) than in any other oil investigated. This mixture resulted in low interfacial tension and moderate viscosity, which seemed to be the optimum oil phase. In addition, to increase the concentration of tetrazepam, an emulsion formulation containing 30% oil phase was produced and optimized. The drug-free emulsion formulation showed fine particle sizes with an imperceptible change in physicochemical properties after more than 2 years on the shelf. As a result, it was possible to produce a parenteral emulsion formulation containing 10 mg/ml tetrazepam. No change in the physicochemical properties of the emulsion was observed after the addition of tetrazepam. The tetrazepam emulsion showed stable behavior during the autoclaving process and good shelf stability for at least 10 months as well. Tetrazepam itself also displayed good stability during the autoclaving process and also showed good shelf stability in this emulsion formulation.

Novelty-elicited mismatch negativity in patients with schizophrenia on admission and discharge

OBJECTIVE

Given recent reports of differences between mismatch negativity (MMN) elicited by always novel sounds (novelty-elicited MMN) and that elicited by repeated rare deviants (conventional MMN), we investigated novelty-elicited MMN and P3a in patients with schizophrenia before and after a nonstandardized inpatient treatment.

DESIGN

Electrophysiological and clinical assessment of patients on admission and discharge from hospital. Assessment of control subjects on 2 sessions.

SETTING

Inpatient treatment in a psychiatric university hospital.

SUBJECTS

20 patients with schizophrenia and 21 healthy control subjects of similar age and sex. Selection of patients with first- to third-episode schizophrenia.

OUTCOME MEASURES

Early and late component MMN amplitudes and latencies, P3a amplitudes and latencies, Positive and Negative Syndrome Scale (PANSS), Global Assessment of Functioning (GAF), Extrapyramidal Symptom Scale (EPS), Abnormal Involuntary Movement Scale (AIMS) and chlorpromazine equivalents.

RESULTS

In patients with schizophrenia, novelty-elicited MMN was unimpaired on admission, and there was a statistically significant reduction of the late MMN component with treatment. Improvements in symptom expression were associated with increased latencies of the early MMN component.

CONCLUSION

Results indicate differences in information processing between conventional and novelty-elicited MMN. Some components of the novelty-elicited MMN might be more state dependent than those of the conventional MMN.

Characterization of co-polymers of lactic and glycolic acid for supercritical fluid processing

Polymers of lactic and glycolic acid are often used for the production of injectible microparticles with controlled drug release. In the variety of processes used for the microparticle formulation, the Aerosol Solvent Extraction System (ASES) is rather special. Microparticle formation and drying take place in one step by precipitating a methylene chloride solution of the polymer in supercritical CO2. This process sets special requirements to the polymers in crystallinity, solubility, and thermal behavior that are best fulfilled by blocked copolymers. This study investigates a number of lactide-co-glycolide polymers with blocked distribution of the co-monomers by NMR spectroscopy and powder diffraction. The molar ratios are determined by 1H-NMR spectroscopy to verify the manufacturer's declarations of the purchased specimens. Additionally, the block length is determined by application of 13C-NMR. Therefore, a method reported in the literature was modified and evaluated in order to calculate the length of lactide and glycolide sequences in the polymer. Furthermore, this study looks at the impact of synthesis conditions on block length and crystallinity, and the impact of the blocking on both, crystallinity and solubility of the polymers.

Neuropsychological and conditioned blocking performance in patients with schizophrenia: assessment of the contribution of neuroleptic dose, serum levels and dopamine D2-receptor occupancy

Patients with schizophrenia show impairments of attention and neuropsychological performance, but the extent to which this is attributable to antipsychotic medication remains largely unexplored. We describe here the putative influence of the dose of antipsychotic medication (chlorpromazine equivalents, CPZ), the antipsychotic serum concentration of dopamine (DA) D2-blocking activity and the approximated central dopamine D2-receptor occupancy (DA D2-occupancy), on conditioned blocking (CB) measures of attention and performance on a neuropsychological battery, in 108 patients with schizophrenia (compared with 62 healthy controls). Antipsychotic serum concentration and D2-occupancy were higher in patients with a paranoid versus non-paranoid diagnosis, and in female versus male patients (independent of symptom severity). Controlling for D2-occupancy removed the difference between high CB in paranoid and impaired low CB in non-paranoid patients. Similar partial correlations for antipsychotic drug dose and serum levels of DA D2-blocking activity with performance of the trail-making and picture completion tests (negative) and the block-design task (positive) showed the functional importance of DA-related activity. High estimates of central DA D2-occupancy were related to impaired verbal fluency but were associated with improved recall of stories, especially in paranoid patients. This, the first study of its kind, tentatively imputes a role for DA D2-related activity in left frontal (e.g. CB, verbal fluency) and temporal lobe functions (verbal recall) as well as in some non-verbal abilities mediated more in the right hemisphere in patients with schizophrenia.

The influence of alkali fatty acids on the properties and the stability of parenteral O/W emulsions modified with solutol HS 15

Arachis oil based parenteral O/W emulsions were prepared using soya bean phosphatidylcholine (SPC) and different combinations of co-emulsifiers containing polyethylene glycol fatty acid esters (Solutol HS 15) and alkali fatty acids (sodium laurate, sodium stearate). The parameters measured were droplet size (both by photon correlation spectroscopy and laser diffractometry), pH and zeta potential. All emulsions were subjected to autoclaving. The addition of polyethylene glycol 12-hydroxy stearate (Solutol HS 15) led to a significant decrease of mean oil droplet size. For long-term stability the amount added turned out to be the most important factor. With increased amounts of Solutol HS 15 the packing density of the emulsifier layer and the zeta potential decreased leading to instability. The optimum load of Solutol HS 15 was found to be 15 micromol/ml. Alkali fatty acids markedly improved the physical stability of the emulsions. Improved stability properties conferred to emulsions by alkali fatty acids could be attributed to the zeta potential increase even in the presence of Solutol HS 15. Consequently a mixed emulsifier film was established in which the ionized fatty acids determined the interface charge. In addition to this a strengthening of the molecular interactions occurring between phospholipid and Solutol HS 15 emulsifier in the presence of ionized fatty acids at the O/W interface can be assumed (L. Rydhag, The importance of the phase behaviour of phospholipids for emulsion stability, Fette Seifen Anstrichm. 81 (1979) 168-173). Different co-emulsifier mixtures were shown to have a pronounced impact on the plasma protein adsorption onto emulsion droplets.

Influence of the acid type on the physical and drug liberation properties of chitosan-gelatin sponges

The influence of acid type used to dissolve chitosan on the resulting sponge physical properties, and their consequent effect on the drug liberation were investigated. Chitosan was dissolved in different acid solutions and chitosan-gelatin sponges were produced by frothing up the polymer solution and then freeze-drying the foam. Prednisolone was used as a model drug. Using tartaric or citric acid resulted in instable, soft, elastic and disintegrating sponges with fast drug release. Elastic but harder sponges from stable foams were obtained when hydrochloric or lactic acid were used. The use of acetic or formic acid enabled the production of stable foams, soft and elastic sponges and a slow drug release. The rate of drug release was decreased by crosslinking the polymers with glutaraldehyde, but only if acetic, formic or acetic acid were used. Therefore, it is possible to manipulate the mechanical properties and the drug liberation rate by using different acids to dissolve chitosan.

Lipid emulsions as a novel system to reduce the hemolytic activity of lytic agents: mechanism of the protective effect

The hemolytic activity of sodium oleate, a high lytic agent, was investigated in different surfactant solutions and lipid emulsion formulations. A new explanation of the protective function of these systems is proposed. It was found that the hemolytic activity of the lytic agent was greatly decreased in solutions and/or dispersions with the surfactant Cremophor EL, Solutol H16 and phospholipids, which can usually build a micellar or liposomal structure. In the case of F68, where the micelle formation is still controversial, the hemolytic activity of the lytic agent was practically not affected and complete hemolysis was observed. In contrast to this, all emulsion formulations, independent of the emulsifier type, showed a stable erythrocyte behavior. Additionally, in the case of lipid emulsions only, a larger amount of the lytic agent could be added without any remarkable increase in the hemolytic activity. As an explanation for these effects it is proposed that the lytic agent is either incorporated into the lipophilic core or intercalates between the emulsifier molecules at the interface. This decreases the direct contact of the lytic agent with the erythrocyte membrane. As a result, the erythrocytes will effectively be protected from hemolytic damage, which can otherwise be induced by such substances.

A rapid and quantitative method for total fatty acid analysis of fungi and other biological samples

A quantitative method for the one-step esterification and determination of absolute amounts of polyunsaturated fatty acids in biotechnologically produced fungal mycelia is proposed. A system of two internal standards was used to quantify the total fatty acid content of the samples by gas chromatography. The degree of methylation of the analyzed fatty acids was calculated using the internal standards, and subsequently this quotient was used to validate the derivatization and extraction reactions. By utilizing this degree of methylation, the corrected amounts of the various fatty acids in the sample can be calculated.

In vitro investigation of the effect of various isotonic substances in parenteral emulsions on human erythrocytes

The hemolytic behaviour of human erythrocytes in parenteral emulsions containing various isotonizing substances (xylitol, sorbitol and glycerol) was studied. It was found that complete hemolysis of human erythrocytes occurred in parenteral emulsions with isotonic or isosmotic concentration of glycerol after 5 min, whereas emulsions which contained an isotonic concentration of xylitol or sorbitol did not show any hemolysis after 40 min. Conversely, formulations with different concentrations of glycerol in an isotonic solution of sorbitol did not show any hemolytic behaviour after 40 min. It appeared that all the hemolytic phenomena encountered in glycerol were of an isotonic character since hemolysis was totally prevented by the inclusion of an isotonic concentration of sorbitol. According to these in vitro results it seems that glycerol, a commonly used substance in commercial parenteral emulsions, may not be the best isotonizing substance.