Radiological and laboratory prognostic parameters for gastric dilation in rabbits (Oryctolagus cuniculus)

BACKGROUND

The aim of this study was to evaluate the radiographical and laboratory findings in pet rabbits with gastric dilation (GD) and identify prognostic parameters.

METHODS

One hundred and fifty-five rabbits with GD were included for the radiographical analyses and 75 for the laboratory analyses. A vertebral stomach score (VSS) was established to determine the extension of the stomach on lateral radiographs. In addition, the caudal limit of gastric distention and the extension and position of gas accumulation in the stomach were recorded.

RESULTS

The VSS was significantly higher in rabbits with GD than in healthy rabbits (p = 0.001). Extensive amounts of gas accumulation in the stomach (p = 0.001) and a ventral or central location of gas accumulation (p = 0.023) were associated with significantly increased mortality. Azotemia (51%), hyperglycaemia (44%) and hyponatraemia (37%) were the most frequent biochemical alterations in rabbits with GD.

LIMITATIONS

Due to the retrospective nature of the data, the cause of GD could not be determined in all animals.

CONCLUSION

Rabbits with GD and severe alterations in glucose, creatinine and sodium concentrations, ventral or central gas accumulations and a large amount of gas in the stomach had a poor prognosis.

Tufted angiomas of the head and neck

BACKGROUND

Tufted angiomas (TAs) are uncommon benign vascular tumors mostly located cutaneously or subcutaneously in the skin of the neck and upper trunk, which appear during childhood and grow slowly. TAs are a variant of lobular capillary hemangiomas. This is the first study to provide an overview of the current literature in combination with the authors' own clinical experience on this rare entity in the head and neck area with non-dermatological localization.

METHODS

A selective Medline and Google Scholar database search was performed. Additionally, we conducted an ICD-10-based database search on hemangiomas (D18.0) in the Charité SAP patient records.

RESULTS

We identified 13 reports in the literature consisting of 16 cases of TA of the head and neck. Males were predominantly affected by TAs (70.6%). The mean age of the patients at the time of surgery was 31.5 years; the mean maximum diameter of the tumors was 16.3 mm. Additionally, we report on one case of TA in our Department of Head and Neck Surgery. A male patient presented with swelling and redness of the left upper eyelid. Radiological examination with computed tomography showed a suprabulbar tumor with a diameter of 13 mm. The tumor was surgically removed via a transcutaneous blepharoplasty approach with the patient under general anesthesia.

DISCUSSION

There is only one other case report on the surgical excision of an intra-orbital TA described to date. Here, we present an epidemiological overview, therapeutic considerations, and differential diagnoses.

[Tufted angiomas of the head and neck. German version]

BACKGROUND

Tufted angiomas (TAs) are uncommon benign vascular tumors mostly located cutaneously or subcutaneously in the skin of the neck and upper trunk, which appear during childhood and grow slowly. TAs are a variant of lobular capillary hemangiomas. This is the first study to provide an overview of the current literature in combination with the authors' own clinical experience on this rare entity in the head and neck area with non-dermatological localization.

METHODS

A selective Medline and Google Scholar database search was performed. Additionally, we conducted an ICD-10-based database search on hemangiomas (D18.0) in the Charité SAP patient records.

RESULTS

We identified 13 reports in the literature consisting of 16 cases of TA of the head and neck. Males were predominantly affected by TAs (70.6%). The mean age of the patients at the time of surgery was 31.5 years; the mean maximum diameter of the tumors was 16.3 mm. Additionally, we report on one case of TA in our Department of Head and Neck Surgery. A male patient presented with swelling and redness of the left upper eyelid. Radiological examination with computed tomography showed a suprabulbar tumor with a diameter of 13 mm. The tumor was surgically removed via a transcutaneous blepharoplasty approach with the patient under general anesthesia.

DISCUSSION

There is only one other case report on the surgical excision of an intra- orbital TA described to date. Here, we present an epidemiological overview, therapeutic considerations, and differential diagnoses.

Mildly oxidized HDL decrease agonist-induced platelet aggregation and release of pro-coagulant platelet extracellular vesicles

Stored platelet concentrates (PLCs) for therapeutic purpose, develop a platelet storage lesion (PSL), characterized by impaired platelet (PLT) viability and function, platelet extracellular vesicle (PL-EV) release and profound lipidomic changes. Whereas oxidized low-density lipoprotein (oxLDL) activates PLTs and promotes atherosclerosis, effects linked to oxidized high-density lipoprotein (oxHDL) are poorly characterized. PLCs from blood donors were treated with native (nHDL) or mildly oxidized HDL (moxHDL) for 5days under blood banking conditions. Flow cytometry, nanoparticle tracking analysis (NTA), aggregometry, immunoblot analysis and mass spectrometry were carried out to analyze PL-EV and platelet exosomes (PL-EX) release, PLT aggregation, protein expression, and PLT and plasma lipid composition. In comparison to total nHDL, moxHDL significantly decreased PL-EV release by -36% after 5days of PLT storage and partially reversed agonist-induced PLT aggregation. PL-EV release positively correlated with PLT aggregation. MoxHDL improved PLT membrane lipid homeostasis through enhanced uptake of lysophospholipids and their remodeling to corresponding phospholipid species. This also appeared for sphingomyelin (SM) and d18:0/d18:1 sphingosine-1-phosphate (S1P) at the expense of ceramide (Cer) and hexosylceramide (HexCer) leading to reduced Cer/S1P ratio as PLT-viability indicator. This membrane remodeling was associated with increased content of CD36 and maturation of scavenger receptor-B1 (SR-B1) protein in secreted PL-EVs. MoxHDL, more potently than nHDL, improves PLT-membrane lipid homeostasis, partially antagonizes PL-EV release and agonist-induced PLT aggregation. Altogether, this may be the result of more efficient phospho- and sphingolipid remodeling mediated by CD36 and SR-B1 in the absence of ABCA1 on PLTs. As in vitro supplement in PLCs, moxHDL has the potential to improve PLC quality and to prolong storage.

One Step Production of High-performance Sandwich Components

The combined PU spray and wet pressing process allows the manufacture of parts with high lightweight potential. The process can be used for the production of sandwich parts with compact continuous fiber reinforced PU outer layers and a process integrated formation of the foam core. Compared with established production processes for structural sandwich parts, the integration of the foam core formation in a wet pressing process is highly efficient and economical especially for complex structural parts.

Seasonal differences of tympanogram and middle ear findings in children

BACKGROUND

It is a known fact that bacterial or viral acute otitis media occurs more frequently in the winter months. Only a few older studies on seasonal differences in middle ear findings are available. These studies are based solely on tympanography, without correlation to intraoperative middle ear findings. This study addresses the question of whether seasonal differences can be found in the preoperative tympanogram and in the corresponding intraoperative findings in children with chronic middle ear problems.

PATIENTS AND METHODS

This retrospective study included patients who had undergone myringotomy with or without tympanostomy tube insertion at the Charité-Universitätsmedizin Berlin between January and December 2011. Corresponding to the catarrhal phases, winter months were defined as those from November to April; summer months from May to October. The preoperative tympanogram and the documented intraoperative middle ear finding were statistically analyzed for seasonal differences.

RESULTS

A total of 654 ears from 206 male and 127 female patients with mean age 3.7 ± 2.5 years were analyzed. In the majority of cases, a type B tympanogram was found (n = 376; 57.5%), whereas the middle ear was filled with air in 19.1% of cases. No significant seasonal differences were found for either the intraoperative middle ear findings or the preoperative tympanograms (p > 0.05).

CONCLUSION

For children with a typical history of chronic otitis media without effusion and chronic tube ventilation dysfunction, myringotomy with or without tympanostomy tube insertion is indicated independently of the season. The results indicate that a wait-and-see approach with hope of improvement during the summer months is not rational.

[Effectivity of early psychosocial counselling for family caregivers in general practioner based dementia care]

BACKGROUND

Psychoeducation and professional support of family caregivers are regarded as important aspects in dementia care. In the context of a general practitioner's (GP) based dementia care project we investigated if professional counselling after making a diagnosis of dementia can reduce the development of depression in family caregivers.

METHODS

42 patients with dementia and their family caregivers took part in the prospective, randomized study with a follow-up after 18 months. 29 families received psychosocial counselling, the control group was provided an information brochure about dementia including helpful contact addresses. Counselling included education about the illness. Additionally, the current individual needs were identified and assistance was administered if necessary.

RESULTS

The counseling was rated as "very helpful" or "helpful" by most of the caregivers as well as by the partaking GPs. While depression rate between counseling and control group did not differ significantly at baseline, the depression rate was significantly increased in the control group after 18 month as compared to the intervention group.

CONCLUSION

Despite the small study size we provide first strong evidence that early psychosocial counselling can reduce the development of depression in family caregivers. Early, professional counselling improves the quality of dementia care within a GP-based dementia care setting and it might stabilize and extend the home care duration of dementia patients.

[Tonsil protrusion in the case of an infraauricular mass. A rare iceberg tumor]

We report on a very rare case of iceberg tumor. A giant lipoma arising from the deep lobe of the parotid gland led to an infraauricular mass and tonsil protrusion. After appropriate imaging (ultrasound and MRI) surgical resection was performed. Tonsil protrusions require differential diagnostic evaluation. Apart from the most prevalent parotid gland tumors, like pleomorphic adenoma and cystadenolymphoma, one must consider rare lipomas. Malignancy (e.g. liposarcoma) can only be excluded by histological examination of the whole specimen.

Colonization of residents and staff of a long-term-care facility and adjacent acute-care hospital geriatric unit by multiresistant bacteria

Long-term-care facilities (LTCFs) are reservoirs of resistant bacteria. We undertook a point-prevalence survey and risk factor analysis for specific resistance types among residents and staff of a Bolzano LTCF and among geriatric unit patients in the associated acute-care hospital. Urine samples and rectal, inguinal, oropharyngeal and nasal swabs were plated on chromogenic agar; isolates were typed by pulsed-field gel electrophoresis; resistance genes and links to insertion sequences were sought by PCR; plasmids were analysed by PCR, restriction fragment length polymorphism and incompatibility grouping. Demographic data were collected. Of the LTCF residents, 74.8% were colonized with ≥1 resistant organism, 64% with extended-spectrum β-lactamase (ESBL) producers, 38.7% with methicillin-resistant Staphylococcus aureus (MRSA), 6.3% with metallo-β-lactamase (MBL) producers, and 2.7% with vancomycin-resistant enterococci. Corresponding rates for LTCF staff were 27.5%, 14.5%, 14.5%, 1.5% and 0%, respectively. Colonization frequencies for geriatric unit patients were lower than for those in the LTCF. Both clonal spread and plasmid transfer were implicated in the dissemination of MBL producers that harboured IncN plasmids bearing bla(VIM-1), qnrS, and bla(SHV-12). Most (44/45) ESBL-producing Escherichia coli isolates had bla(CTX-M) genes of group 1; a few had bla(CTX-M) genes of group 9 or bla(SHV-5); those with bla(CTX-M-15) or bla(SHV-5) were clonal. Risk factors for colonization of LTCF residents with resistant bacteria included age ≥86 years, antibiotic treatment in the previous 3 months, indwelling devices, chronic obstructive pulmonary disease, physical disability, and the particular LTCF unit; those for geriatric unit patients were age and dementia. In conclusion, ESBL-producing and MBL-producing Enterobacteriaceae and MRSA were prevalent among the LTCF residents and staff, but less so in the hospital geriatric unit. Education of LTCF employees and better infection control are proposed to minimize the spread of resistant bacteria in the facility.

A new model of primary human adipocytes reveals reduced early insulin signalling in type 2 diabetes

The aim of this study was to establish a diabetic model of primary human adipocytes for investigating potential defects in early insulin signalling. Specimens of human subcutaneous adipose tissue were obtained during orthopaedic surgical procedures. Preadipocytes were isolated and differentiated to adipocytes. Western blot analysis and immunoprecipitation were performed to determine protein content of IRS-1, IRS-2, p85, phosphorylation of IRS-1, IRS-2, Akt and MAPK as well as association between p85 and IRS-1/IRS-2. In addition to short-term insulin stimulation, the effect of hyperinsulinaemia was investigated by treating cells with insulin over a period of 36 hours. We found a significantly reduced basal expression of IRS-1 (54 +/- 15%) in adipocytes from type 2 diabetic subjects compared to controls with a further significant reduction in expression after long-term treatment (30 +/- 12%) compared to short-term treatment. IRS-2 expression also showed a significant reduction under hyperinsulinaemic conditions (20 +/- 2%) in diabetics vs. controls. Furthermore, long-term treatment with insulin in diabetic adipocytes led to a significant reduction in the phosphorylation of IRS-1(68 +/- 11%), IRS-2 (82 +/- 11%), Akt (42 +/- 2%), and MAPK (92 +/- 12%) and in the subsequent association between p85 to IRS-1 and IRS-2 (100 +/- 16% and 96 +/- 12%) in comparison to controls. Investigating glucose uptake diabetic adipocytes revealed a significant reduction of 90 +/- 2%. In this study, we were able to establish a new diabetic model of primary human adipocytes. A defect in early insulin signalling in type 2 diabetic patients under hyperinsulinaemic conditions was determined. These results might help to give further insights in early insulin action; additionally, this human model represents a useful target for the study of new therapeutic approaches.

LDL-oxidation and -subgroups in normo- and hypertensive patients with and without a family history of hypertension

OBJECTIVES

Oxidative modification of low-density-lipoprotein (LDL) increases its atherogenic potential to induce the accumulation of lipids and cells in the vascular wall. Patients have different lipoprotein profiles according to their LDL-subgroup pattern. The subgroup of LDL, which is most susceptible to oxidation, is most likely the dense LDL3 subfraction. In order to study an assumed association between hypertension, LDL subgroup distribution and the susceptibility of LDL to oxidation, 14 normotensive patients without family histories of hypertension (NT), 13 normotensive patients with family histories of hypertension (NT-FH), 10 hypertensive patients without family histories of (HT) and 11 hypertensive patients with family histories of hypertension (HT-FH) were evaluated.

PATIENTS AND METHODS

LDL was oxidatively modified by incubation with copper ions (1.6 microM/L). The course of LDL-oxidation was measured in vitro by continuous photometric monitoring and the quantitative distribution of 3 LDL-subgroups by capillary isotachophoresis (ITP).

RESULTS

The lag-phases of NT-FH and hypertensive patients were shorter than those of the control group (NT: 116 +/- 36 minutes; NT-FH 92 +/- 32 minutes, p < 0.05; HT: 95 +/- 41 minutes; HT-FH: 76 +/- 33 minutes, p < 0.05). Compared to NT a significant difference in the relative preponderance of LDL3 subgroup was observed for HT-FH (23.5 +/- 4.6% versus NT: 19.3 +/- 6.6%), additionally, statistical analysis showed a similar trend amongst the other patient groups (NT-FH: 20.4 +/- 7.4%, HT: 21.4 +/- 4.6%).

CONCLUSIONS

The increased occurrence of the LDL3 subgroup might contribute to a higher susceptibility to LDL oxidation and therefore create an increased risk of vascular disease in the genotypic and phenotypic hypertensive patient population.

Lipopolysaccharide and ceramide docking to CD14 provokes ligand-specific receptor clustering in rafts

The glycosylphosphatidylinositol-anchored receptor CD14 plays a major role in the inflammatory response of monocytes to lipopolysaccharide. Here, we describe that ceramide, a constituent of atherogenic lipoproteins, binds to CD14 and induces clustering of CD14 to co-receptors in rafts. In resting cells, CD14 was associated with CD55, the Fcgamma-receptors CD32 and CD64 and the pentaspan CD47. Ceramide further recruited the complement receptor 3 (CD11b/CD18) and CD36 into proximity of CD14. Lipopolysaccharide, in addition, induced co-clustering with Toll-like receptor 4, Fcgamma-RIIIa (CD16a) and the tetraspanin CD81 while CD47 was dissociated. The different receptor complexes may be linked to ligand-specific cellular responses initiated by CD14.

Homogeneous assay based on 52 primer sets to scan for mutations of the ABCA1 gene and its application in genetic analysis of a new patient with familial high-density lipoprotein deficiency syndrome

Familial high-density lipoprotein (HDL)-deficiency syndromes are caused by mutations of the ABCA1 gene, coding for the ATP-binding cassette transporter 1. We have developed a homogeneous assay based on 52 primer sets to amplify all 50 ABCA1 exons and approximately 1 kb of its promoter. The assay allows for convenient amplification of the gene from genomic DNA and easy mutational analysis through automatic sequencing. It obviates the need to use mRNA preparations, which were difficult to handle and posed a risk to miss splice junction or promoter mutations. The application of the test to the molecular analysis of a new patient with familial HDL-deficiency (Tangier disease) led to a discovery of two novel ABCA1 mutations: C2665del and C4457T.

ApoE-containing high density lipoproteins and phospholipid transfer protein activity increase in patients with a systemic inflammatory response

High density lipoproteins (HDL) mediate reverse cholesterol transport as well as the clearance of oxidation products or inflammatory mediators, thereby contributing to tissue integrity. The decrease in HDL in inflammation has been attributed to decreased lecithin:cholesterol acyltransferase activity, whereas the role of phospholipid transfer protein (PLTP) and cholesteryl ester transfer protein has not been analyzed in detail. We have studied the activities of HDL-modifying proteins and the heterogeneity of HDL in healthy control subjects and three groups of postsurgery patients: no bacterial infection (group 1), bacterial focus and systemic inflammatory response (group 2), and severe sepsis (group 3). For all patients, a decrease in total HDL could be demonstrated, with a loss of mainly large, apolipoprotein A-I (apoA-I) HDL particles, an almost total loss of apoC-I, and an increase in apoE HDL (200-500 kDa), which did not contain significant amounts of apoA-I, apoA-II, or apoC-I. PLTP activity was increased in patients of groups 2 and 3, paralleled by a redistribution of PLTP into a population of small (120- to 200-kDa) particles, probably representing PLTP homodimers or lipid-complexed PLTP. In summary, the increase in apoE HDL and PLTP activity may improve the delivery of energy substrates and phospholipids to tissues that must maintain cellular membrane homeostasis under conditions of inflammatory stress.

Preparative free-solution isotachophoresis for separation of human plasma lipoproteins: apolipoprotein and lipid composition of HDL subfractions

We have previously shown that plasma lipoproteins can be separated by analytical capillary isotachophoresis (ITP) according to their electrophoretic mobility in a defined buffer system. As in lipoprotein electrophoresis, HDL show the highest mobility followed by VLDL, IDL, and LDL. Chylomicrons migrate according to their net-charge between HDL and VLDL, because ITP has negligible molecular sieve effects. Three HDL subfractions were obtained which were designated fast-, intermediate-, and slow-migrating HDL. To further characterize these HDL subfractions, a newly developed free-solution ITP (FS-ITP)-system was used, that allows micro-preparative separation of human lipoproteins directly from whole plasma (Böttcher, A. et al. 1998. Electrophoresis. 19: 1110-1116). The fractions obtained by FS-ITP were analyzed for their lipid and apolipoprotein composition and by two-dimensional nondenaturing polyacrylamide gradient gel electrophoresis (2D-GGE) with subsequent immunoblotting. fHDL are characterized by the highest proportion of esterified cholesterol of all three subfractions and are relatively enriched in LpA-I. Together with iHDL they contain the majority of plasma apoA-I, while sHDL contain the majority of plasma apoA-IV, apoD, apoE, and apoJ. Pre-beta-HDL were found in separate fractions together with triglyceride-rich fractions between sHDL and LDL. In summary, ITP can separate the bulk of HDL into lipoprotein subfractions, which differ in apolipoprotein composition and electrophoretic mobility. While analytical ITP permits rapid separation and quantitation for diagnostic purposes, FS-ITP can be used to obtain these lipoprotein subfractions on a preparative scale for functional analysis. As FS-ITP is much better suited for preparative purposes than gel electrophoresis, it represents an important novel tool for the functional analysis of lipoprotein subclasses.

Transport of lipids from golgi to plasma membrane is defective in tangier disease patients and Abc1-deficient mice

Mutations in the gene encoding ATP-binding cassette transporter 1 ( ABC1) have been reported in Tangier disease (TD), an autosomal recessive disorder that is characterized by almost complete absence of plasma high-density lipoprotein (HDL), deposition of cholesteryl esters in the reticulo-endothelial system (RES) and aberrant cellular lipid trafficking. We demonstrate here that mice with a targeted inactivation of Abc1 display morphologic abnormalities and perturbations in their lipoprotein metabolism concordant with TD. ABC1 is expressed on the plasma membrane and the Golgi complex, mediates apo-AI associated export of cholesterol and phospholipids from the cell, and is regulated by cholesterol flux. Structural and functional abnormalities in caveolar processing and the trans-Golgi secretory pathway of cells lacking functional ABC1 indicate that lipid export processes involving vesicular budding between the Golgi and the plasma membrane are severely disturbed.

The gene encoding ATP-binding cassette transporter 1 is mutated in Tangier disease

Tangier disease (TD) is an autosomal recessive disorder of lipid metabolism. It is characterized by absence of plasma high-density lipoprotein (HDL) and deposition of cholesteryl esters in the reticulo-endothelial system with splenomegaly and enlargement of tonsils and lymph nodes. Although low HDL cholesterol is associated with an increased risk for coronary artery disease, this condition is not consistently found in TD pedigrees. Metabolic studies in TD patients have revealed a rapid catabolism of HDL and its precursors. In contrast to normal mononuclear phagocytes (MNP), MNP from TD individuals degrade internalized HDL in unusual lysosomes, indicating a defect in cellular lipid metabolism. HDL-mediated cholesterol efflux and intracellular lipid trafficking and turnover are abnormal in TD fibroblasts, which have a reduced in vitro growth rate. The TD locus has been mapped to chromosome 9q31. Here we present evidence that TD is caused by mutations in ABC1, encoding a member of the ATP-binding cassette (ABC) transporter family, located on chromosome 9q22-31. We have analysed five kindreds with TD and identified seven different mutations, including three that are expected to impair the function of the gene product. The identification of ABC1 as the TD locus has implications for the understanding of cellular HDL metabolism and reverse cholesterol transport, and its association with premature cardiovascular disease.

Inhibition of thermolysin and human alpha-thrombin by cobalt(III) Schiff base complexes

Cobalt(III) Schiff base complexes have been shown to inhibit the replication of the ocular herpes virus. It is well known that these complexes have a high affinity for nitrogenous donors such as histidine residues, and it is possible that they bind to (and inhibit) an enzyme that is crucial to viral replication. In model studies, we have found that [Co(acacen)(NH3)2]+ is an effective irreversible inhibitor of thermolysin at millimolar concentrations; it also inhibits human alpha-thrombin. Axial ligand exchange with an active-site histidine is the proposed mechanism of inhibition. The activity of thermolysin and thrombin can be protected by binding a reversible inhibitor to the active site before addition of the cobalt(III) complex.

Automated free-solution isotachophoresis: instrumentation and fractionation of human serum proteins

An automated free-solution isotachophoresis system (FS-ITP) for preparative fractionation of biopolymers is described, operated in a batch mode. The dimension of the separation chamber allows an up to 1200-fold higher sample load compared to separation in capillaries of 180 microm inner diameter as used in analytical capillary isotachophoresis (C-ITP). The preparative capacity of the system is within the milligram range. The method is fully compatible with analytical C-ITP, which is essential for preparative-scale isotachophoresis with regard to optimization of electrolyte systems and the search for suitable spacers. As a model application the fractionation of human serum proteins is reported. The collected fractions were analyzed by C-ITP and agarose gel electrophoresis.

Preparation of Golgi subfractions with free-solution isotachophoresis: analysis of sphingomyelin synthesis in Golgi subfractions from rat liver

A new displacement electrophoresis technique, termed free-solution isotachophoresis (FS-ITP) was used for the analysis of sphingolipid metabolism in Golgi subfractions. The discontinuous electrolyte system enables tissue-derived membrane vesicles to be separated and purified due to their polarity patterns in a mobility gradient. In this study total Golgi apparatus obtained from rat liver by discontinuous density gradient centrifugation was subfractionated by preparative FS-ITP, yielding enzymatically active cis-, medial-, and trans-Golgi subfractions. These membrane vesicles were assayed by the following established enzyme marker activities: NADH cytochrome c reductase (cis-Golgi), NADP phosphatase (medial-Golgi), and thiamine pyrophosphatase (trans-Golgi). The activity of phosphatidylcholine:ceramide phosphocholine transferase, a sphingomyelin synthesizing enzyme, is attributed to the cis- and medial-Golgi-derived subfractions. Analysis of Golgi lipids revealed a decline in membranous ceramide along the cis- to trans-Golgi polarity axis. Furthermore, significant amounts of newly synthesized sphingomyelin and diacylglycerol are transferred from the medial/cis- to the trans-Golgi compartment. The FS-ITP system is well suited for micropreparative experimental applications, as demonstrated by studies on phosphatidylcholine:ceramide phosphocholine transferase activity in Golgi membrane vesicles of rat liver obtained by FS-ITP.

Temperature dependent intermediate structures during the main phase transition of dimyristoyl phosphatidylcholine vesicles a combined iodine laser-temperature jump and time resolved cryo-electron microscopy study

The kinetics of the main phase transition of dimyristoylphosphatidyl choline (DMPC) unilamellar vesicles were investigated in the time range from microseconds to seconds. Iodine laser-temperature jump (ILTJ) experiments showed three discrete relaxation phenomena. Time resolved cryo-electron microscopy (CEM) was applied to produce images of intermediate states typical for the relaxation times of lipid vesicles in the micro- to millisecond time window. A careful measurement of the rate of temperature decrease observed during the production of vitrified lamellae of aqueous samples on a copper grid was performed. The best conditions resulted in average rates of cooling of 3 x 10(4) K/s. By comparing the images from CEM of DMPC vesicle samples vitrified above, at, and below the phase transition temperature a structural model was designed, which explains the temperature jump relaxation times in the micro- to millisecond time range by the formation and disappearance of coexisting clusters of crystalline, intermediate, and fluid lipid areas inside the DMPC bilayers.

Purification, cloning, and expression of a human enzyme with acyl coenzyme A: cholesterol acyltransferase activity, which is identical to liver carboxylesterase

An enzyme with acyl coenzyme A:cholesterol acyltransferase (ACAT) activity was isolated from porcine liver, and sequences derived from trypsinized peptides indicated homology to liver carboxylesterase. By use of degenerate primers, human cDNA clones were identified, which were identical to human liver carboxylesterase. Expression of the full-length cDNA in Chinese hamster ovary (CHO) cells led to an approximately threefold increase in cellular ACAT activity. This was accompanied by an approximately 20-fold increase of cellular cholesteryl ester content. By light and electron microscopy, recombinant CHO cells contained numerous lipid droplets that were not present in control CHO cells. Expression of an antisense cDNA in HepG2 cells reduced cellular ACAT activity by 35% compared with control. To further investigate the role of the enzyme in cellular cholesterol homeostasis, regulation of the mRNA was investigated in 7-day cultured human mononuclear phagocytes (MNPs). When these cells were incubated in lipoprotein-deficient serum for 18 hours, the mRNA for ACAT/carboxylesterase was almost not detectable on Northern blots, whereas after incubation with acetylated low-density lipoproteins, a strong hybridization signal was obtained. This is evidence that the mRNA of ACAT/carboxylesterase is induced by cholesterol loading. It is concluded from the data presented that ACAT/carboxylesterase is relevant for cellular cholesterol esterification in vivo. The regulation in MNPs indicates that the enzyme is also involved in foam cell formation during early atherogenesis.

Clusterin (complement lysis inhibitor) forms a high density lipoprotein complex with apolipoprotein A-I in human plasma

Clusterin/human complement lysis inhibitor (CLI) is incorporated stoichiometrically into the soluble terminal complement complex and inhibits the cytolytic reaction of purified complement components C5b-9 in vitro. Using an anti-clusterin affinity column, we found that an additional protein component with a molecular mass of 28-kDa co-purifies with clusterin from human plasma. We show by immunoblotting and amino acid sequencing that this component is apolipoprotein A-I (apoA-I). By using physiological salt buffers containing 0.5% Triton X-100, apoA-I is completely dissociated from clusterin bound to the antibody column. Free clusterin immobilized on the antibody-Sepharose selectively retains apoA-I from total human plasma. Delipidated apoA-I and to a lesser extent ultracentrifugation-purified high density lipoproteins (HDL) adsorbed to nitrocellulose also have a binding affinity for purified clusterin devoid of apoA-I. The isolated apoA-I-clusterin complex contains approximately 22% (w/w) lipids which are composed of 54% (mole/mol) total cholesterol (molar ratio of unesterified/esterified cholesterol, 0.58), 42% phospholipids, and 4% triglycerides. In agreement with the low lipid content, apoA-I-clusterin complexes are detected only in trace amounts in HDL fractions prepared by density ultracentrifugation. In free flow isotachophoresis, the purified apoA-I-clusterin complex has the same mobility as the native clusterin complex in human plasma and is found in the slow-migrating HDL fraction of fasting plasma. Our data indicate that clusterin circulates in plasma as a HDL complex, which may serve not only as an inhibitor of the lytic terminal complement cascade, but also as a regulator of lipid transport and local lipid redistribution.

Macrophage interaction of HDL subclasses separated by free flow isotachophoresis

Preparative isotachophoresis (ITP) was used for the fractionation of fasting and postprandial high density lipoproteins (HDL) according to their net charge in the absence of molecular sieve effects. Three major HDL subpopulations with fast, intermediate, and slow mobility have been recognized. Particle size analysis by gradient gel electrophoresis has shown that in the fast-migrating subpopulation particles dominate with a size of HDL3a and HDL2b. The subpopulation with intermediate mobility contains particles with a size between HDL2a and HDL3b, while in the slow migrating subpopulation particles dominate with a size of HDL2b, HDL3a, and HDL3c. The fast-migrating subpopulation is rich in apoA-I and phosphatidylcholine. The particles of this fraction bind at 4 degrees C to HDL receptors on macrophages with high affinity (KD = 7.71 micrograms/ml; Bmax = 245.6 ng). The subpopulations with intermediate mobility is rich in apoA-II, apoE, C apolipoproteins, cholesteryl esters, and sphingomyelin. Its affinity to HDL receptors (KD = 17.7 micrograms/ml; Bmax = 198.4 ng) is lower than that of the HDL particles in the fast-migrating subfraction. The slow-migrating subpopulation consists of particles rich in apoA-IV and is associated with a high LCAT activity. This fraction expresses the highest nonspecific binding to mouse peritoneal macrophages compared to the other HDL fractions and contains only a small amount of particles that interact with HDL receptors by high affinity binding (KD = 7.3 micrograms/ml; Bmax = 95.9 ng). In 37 degrees C binding experiments the fast-migrating subfraction reveals the highest total cell-associated activity. 72% of which is trypsin-resistant. The other subfractions express a lower total cell-associated activity and 45% of the activity of the intermediate- and 43% of the activity of the slow-migrating fraction is trypsin-sensitive. When the HDL fractions are isolated from postprandial sera of the same donor, the fast-migrating particles bind at 4 degrees C with a higher affinity (KD = 4.6 micrograms/ml) while no significant changes are observed in the intermediate- and slow-migrating subpopulations. The slow- and the fast-migrating HDL subpopulations isolated from fasting serum have a high capacity to promote cholesterol removal from macrophages. We hypothesize that the HDL subpopulations rich in apoA-I promote cholesterol removal predominantly via the interaction with HDL receptors, while apoA-IV-rich HDL particles receive their driving force for cholesterol efflux from the concomitant action of LCAT via a predominantly nonspecific interaction of the particles with the cell surface.(ABSTRACT TRUNCATED AT 400 WORDS)