Simple, rapid enzyme-linked immunosorbent assay (ELISA) for the determination of rat osteocalcin

Determination of the concentration of osteocalcin in rat serum is frequently performed using a commercially available radioimmunoassay (RIA). However, this assay takes 3 days to complete, uses radioactive material, and has a narrow linear range. The limited range of the RIA makes it necessary to test multiple dilutions of the sample which frequently results in values that differ, depending on the dilution. In order to overcome these limitations, we have developed an ELISA that utilizes the same standards and anti-rat osteocalcin antiserum, as is used in the RIA. The principle of the ELISA is that the osteocalcin in the sample competes with osteocalcin previously immobilized on a microtiter plate to bind to the available anti-rat osteocalcin antibodies. The amount of antibody bound to the immobilized osteocalcin is determined colorimetrically using a secondary antibody coupled to alkaline phosphatase. This ELISA has a three-log linear response with a sensitivity of 0.1-0.15 ng/ml and intra- and interassay coefficient of variance (CV) values of less than 10%. Most importantly, the assay is rapid and only requires a 2-hour incubation of the sample with the antiserum. The incubation time is important since we and others have observed a significant decrease in the osteocalcin level from serum samples incubated for long periods of time with the antiserum, presumably due to degradation of the osteocalcin. In general, the commercially available RIA gives osteocalcin values that are one-half to one-fourth that of the ELISA because the RIA requires a 48-hour incubation time.

The Effect of Salt Concentration on Adsorption of Low-Charge-Density Polyelectrolytes and Interactions between Polyelectrolyte-Coated Surfaces

In this investigation surface force, X-ray photoelectron spectroscopy and ellipsometry techniques have been used to study the adsorption of a low-charge-density cationic polyelectrolyte on negatively charged surfaces. It is shown that the low cationicity of this polyelectrolyte induces an adsorption behavior which is limited by steric factors rather than by the substrate surface charge or potential. It is also established that an increase in ionic strength of the solution results in desorption of the polyelectrolyte accompanied by an increase in layer thickness. This phenomenon is typical of a screening-reduced adsorption regime where electrostatic interactions predominate in the adsorption process. An increase in layer thickness most often occurs as a result of an increased adsorbed amount. Here, however, the increase in layer thickness occurs despite a reduction in the adsorbed amount. This can be understood as resulting from a reduced polyelectrolyte-surface affinity and a swelling of the adsorbed layer. Finally, it is demonstrated that the employed techniques complement each other and reveal new information on the interaction forces and conformation of polyelectrolytes at the solid-liquid interface. Copyright 1998 Academic Press.

Efficacy and safety of a new cholesterol synthesis inhibitor, atorvastatin, in comparison with simvastatin and pravastatin, in subjects with hypercholesterolemia

BACKGROUND

High levels of total and LDL-cholesterol are associated with an increased risk of atherosclerotic vascular disease. Lowering of serum cholesterol levels by pharmacologic intervention with inhibitors of cholesterol synthesis, the so-called statins, reduces the incidence of cardiovascular events in subjects with and without atherosclerotic manifestations. In a 16-week, multicenter, randomized, open-label cross-over study we compared the efficacy and safety of the new compound atorvastatin for reducing LDL-cholesterol with simvastatin or pravastatin.

METHODS

Following a 4-week placebo-controlled baseline period patients with LDL-cholesterol between 4.1 and 6.2 mmol/l and serum triglycerides below 3.4 mmol/l were randomly assigned to treatment either with 5 or 20 mg atorvastatin, or with 10 mg simvastatin or 20 mg pravastatin once daily for 4 weeks. After a placebo-washout period of 4-6 weeks, patients switched to the alternate treatment. At the end of weeks 3 and 4 of each study phase the serum concentrations of lipid parameters and apolipoproteins as well as safety parameters were determined.

RESULTS

A total of 78 subjects entered the study. Treatment with 5 mg atorvastatin reduced total and LDL-cholesterol by 21 and 27%, respectively, which was similar to 10 mg simvastatin (total cholesterol -20%, LDL-cholesterol -28%) and 20 mg pravastatin (-18 and -24%, respectively). The effects of this low dose of atorvastatin on triglyceride levels (-16%) was not different from that of simvastatin and pravastatin (-8 and -11%, respectively). Treatment with 20 mg atorvastatin caused significantly larger reductions in total cholesterol (-33%) and LDL-cholesterol (-44%), serum triglycerides (-23%), and apo B (-40%) compared to simvastatin and pravastatin. Atorvastatin was well-tolerated, and no serious or medically important adverse events were observed.

CONCLUSIONS

We conclude that atorvastatin is a safe and very efficacious cholesterol-lowering agent, which also possesses significant triglyceride-lowering properties.

Effects of neuromuscular blocking agents on excitatory transmission and gamma-aminobutyric acidA-mediated inhibition in the rat hippocampal slice

BACKGROUND

Although neuromuscular blocking agents do not cross the blood-brain barrier, they may penetrate the central nervous system under particular circumstances and eventually cause neurotoxic consequences.

METHODS

The effects of neuromuscular blocking agents on excitatory and inhibitory transmission in area CA1 of rat hippocampal slices were investigated using extracellular and intracellular recording techniques.

RESULTS

Application of atracurium in the perfusion medium resulted in a dose-dependent enhancement of excitatory synaptic responses averaging 48.7 +/- 4.3% at a concentration of 10 nM. This effect was correlated with an increase in the size of the presynaptic fiber volley. Laudanosine, but not pancuronium bromide or vecuronium bromide, produced similar changes. In addition, atracurium and laudanosine blocked inhibitory transmission and reduced intracellularly recorded gamma-aminobutyric acidA receptor-mediated potentials. These effects were observed only at concentrations >1 microM and were not reproduced by pancuronium bromide and vecuronium bromide.

CONCLUSIONS

Atracurium and its metabolite, laudanosine, contrary to pancuronium bromide and vecuronium bromide, produce two distinct effects on hippocampal slices. They enhance excitatory transmission and neuronal excitability and they block inhibitory gamma-aminobutyric acidA-mediated synaptic responses.

Glyceraldehyde-3-phosphate dehydrogenase, the putative target of the antiapoptotic compounds CGP 3466 and R-(-)-deprenyl

R-(-)-Deprenyl (Selegiline) represents one of the drugs currently used for the treatment of Parkinson's disease. This compound was shown to protect neurons or glias from programmed cell death in a variety of models. The mechanism of action of neuroprotection as well as inhibition of apoptosis remains elusive. CGP 3466 is a structurally related analog of R-(-)-deprenyl that exhibits virtually no monoamine oxidase type B inhibiting activity but is neuroprotective in the picomolar concentration range. We showed specific binding of CGP 3466 to glyceraldehyde-3-phosphate dehydrogenase by affinity binding, by affinity labeling, and by means of BIAcore(R) technology. Apoptosis assays based on the human neuroblastoma cell line PAJU established the importance of this interaction for mediating drug-induced inhibition of programmed cell death.

Temperature-responsive size-exclusion chromatography using poly(N-isopropylacrylamide) grafted silica

Silica-based packing materials induce non-specific interactions with proteins in aqueous media because of the nature of their surface, mainly silanol groups. Therefore, the silica surface has to be modified in order to be used as stationary phase for the High Performance Size-Exclusion Chromatography (HPSEC) of proteins. For this purpose, porous silica beads were coated with hydrophilic polymer gels (dextrans of different molecular weights) carrying a calculated amount of diethyl-aminoethyl groups (DEAE). Actually, as shown by HPSEC, these dextran modified supports minimize non-specific adsorption for proteins and pullulans in aqueous solution. Then, in order to change the pore size in response to temperature, temperature responsive polymer of poly(N-isopropylacrylamide) (PIPAAm) was introduced into the surface of dextran-DEAE on porous silica beads. The structure of these supports before and after modification was alternately studied by Scanning Electronic Microscopy (SEM) and Scanning Force Microscopy (SFM). An adsorption of radiolabelled albumin was performed to complete our study. Silica modifications by dextran-DEAE and PIPAAm improve the neutrality of the support and minimize the non-specific interactions between the solid support and proteins in solution. At low temperature, the support having PIPAAm exhibits a high resolution domain in HPSEC and finally permits a better resolution of proteins and pullulans. At higher temperature, hydrophobic properties of PIPAAm produce interactions with some proteins and trigger off a slight delay of their elution time.

Influence of the nature of coupling agents on insulin adsorption on supports grafted with sialic acid for high-performance affinity chromatography

Porous silica exhibits excellent mechanical properties for use as a stationary phase for high-performance liquid chromatography. However, negative surface charges make it unusable in its native state. For this reason, silica beads are coated with dextran polymers carrying a calculated amount of diethylaminoethyl groups. Both the minimization of non-specific interactions and the hydrophilic character of such supports allow their functionalization with biospecific ligands and finally their use in high-performance affinity chromatography of biological products. The use of these modified supports in high-performance affinity chromatography requires a better understanding of various characteristics of stationary phases. For this purpose, several techniques were utilized, in particular, size-exclusion chromatography and adsorption of radiolabelled albumin. These methods provided complementary information on the structure of these supports. Coated silica-based supports were functionalized with sialic acid by means of different coupling agents. The affinity of these supports for insulin was determined by the establishment of adsorption isotherms and by high-performance affinity chromatography, to evidence the relationships between structural characteristics of the supports and their separation properties. The study of interactions between these supports and insulin allowed us to show the importance of the coupling method on the performances of supports in affinity chromatography.

High-performance affinity chromatography for the purification of heparin-binding proteins from detergent-solubilized smooth muscle cell membranes

Heparin and heparan sulfates are regulators of cellular events including adhesion, proliferation and migration. In particular, the antiproliferative effect of heparin on smooth muscle cell (SMC) growth is well described. However, its mechanism of action remains unclear. Numerous results suggest an endocytosis mediated by a still unknown heparin receptor on vascular SMCs. In order to identify a putative heparin receptor on SMCs that could be involved in heparin signalling, affinity chromatography supports were developed. In this paper, we describe high-performance liquid affinity chromatography (HPLAC) supports obtained from silica beads coated with dextran polymer substituted by a calculated amount of diethylaminoethyl functions. With a polysaccharide dextran layer, this type of support can be grafted with specific ligands, such as heparin, using conventional coupling methods. In a previous work, we demonstrated, using butanedioldiglycidyl ether, that silica stationary phases coupled to heparin could be used for the fast elution and good peak resolution of heparin-binding proteins. In the present work, an affinity chromatographic fraction of SMC membrane extracts was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and six heparin-binding proteins from dodecyloctaethyleneglycol monoether-solubilized SMCs were observed. Their Mr values were between 40 and 70 kDa, with three major protein bands at 66, 45 and 41 kDa. These results indicate the usefulness of the chromatographic method for purifying heparin binding proteins from SMC membrane.

An in vitro blood-brain barrier model: cocultures between endothelial cells and organotypic brain slice cultures

This communication describes a novel in vitro blood-brain barrier (BBB) model: organotypic slice cultures from the central nervous system were overlaid on endothelial cell monolayers grown on permeable membranes. Morphological, electrophysiological, and microdialysis approaches were carried out to characterize and validate this model. After 10 days in coculture, morphological studies reveal the presence of tight junctions. Electrophysiological recordings of neuronal activity performed on organotypic cultures with or without an endothelial cell monolayer show that amplitude of evoked responses were comparable, indicating good viability of cocultures after 2 weeks. Perfusion of known BBB permeable or nonpermeable molecules was used to test the coculture tightness in conjunction with electrophysiological or microdialysis approaches: application of glutamate (Glu), which doesn't easily cross the BBB, triggers off rhythmic activity only in control cultures, whereas epileptogenic activity was observed in both control cultures and cocultures during perfusions with picrotoxin, a molecule that can diffuse through the BBB. Finally, the microdialysis technique was used to determine the permeability of molecules coming from the perfusion chamber: L-dopa, dopamine, and Glu were employed to assess the selective permeability of the coculture model. Thus, these results indicate that the in vitro model described possesses characteristics similar to those of the BBB in situ and that cocultures of organotypic slices and endothelial cell monolayers have potential as a powerful tool for studying biochemical mechanisms regulating BBB function and drug delivery to the central nervous system.

Vaccination against persistent viral infection exacerbates CD4+ T-cell-mediated immunopathological disease

Lymphocytic choriomeningitis virus (LCMV) infection of normal mice results in a fatal immunopathologic meningitis mediated by CD8+ cytotoxic T lymphocytes (CTL). We have previously shown that female beta2-microglobulin-deficient (beta2m-/-) mice, which are also deficient in CD8+ T cells, are susceptible to LCMV-induced immune-mediated meningitis, characterized by significant weight loss and mortality. This LCMV disease in beta2m-/- mice is mediated by CD4+ T lymphocytes. Our previous studies have also demonstrated that male beta2m-/- mice are less susceptible than female beta2m-/- mice to LCMV-induced, immune-mediated mortality and weight loss. In this report, we show that vaccination of male beta2m-/- mice enhances immunopathology following intracranial infection with LCMV. We observed increased production of gamma interferon (IFN-gamma), an increase in CD4+ CTL precursor frequency, and an increased frequency of IFN-gamma-producing cells from spleen cells of vaccinated male beta2m-/- mice. Vaccinated male beta2m-/- mice also had significantly increased inflammation in the cerebrospinal fluid (CSF), characterized by a large CD4+ T-cell infiltrate. CSF cells from vaccinated mice showed increased production of IFN-gamma on day 7 postchallenge. Neither vaccinated nor control beta2m-/- mice were able to clear virus, and the two groups had similarly high levels of virus early after infection. These results suggest that the magnitude of the early immune response is more important than the level of virus in the brain in determining the outcome of immunopathology in beta2m-/- mice. We show here that vaccination can increase CD4+ T-cell-dependent immunopathology to a persistent viral infection.

Amplification of 11q13 DNA markers in head and neck squamous cell carcinomas: correlation with clinical outcome

This study was performed on 282 patients with primary head and neck squamous cell carcinomas to evaluate the prognostic importance of 11q13 amplification. Amplification of the 11q13 DNA markers, HST-1/FGF-4 and BCL-1, evaluated by Southern and slot blot hybridisation, was detected in 52% of tumours. 11q13 amplification was associated with tumour site since this alteration occurred in 76% of tumours arising in the hypopharynx, versus 40% in the other sites (P = 0.0007). 11q13 amplification was also significantly related to the presence of involved neck lymph nodes (P = 0.013). The relationship between 11q13 amplification and risk of progression was studied in two subgroups of head and neck cancer patients with regard to treatment modalities. The presence of 11q13 amplification in the tumour was not significantly associated with a shorter event-free survival (P = 0.82) and crude survival (P = 0.61) of the 201 patients treated by surgery and postoperative radiotherapy. Similarly, absence of a relationship was observed for the group of 79 patients treated by surgery alone. These results confirm that 11q13 amplification is a prominent event in head and neck squamous cell carcinoma, indicating that it may be a common genetic event in the development of these neoplasms, but is not a reliable prognostic marker.

Staurosporine but not chelerythrine inhibits regeneration in hippocampal organotypic cultures

A mechanical lesion in hippocampal organotypic cultures is followed by a recovery process involving scar formation, sprouting of fibres and formation of new functional synapses. Here we tested the effect of staurosporine and chelerythrine, two protein kinase C (PKC) inhibitors, on this lesion-induced neurite outgrowth of Shaffer collaterals. At a concentration of 1 microM, staurosporine delayed functional recovery assessed by measuring synaptic field potentials across the lesion, without altering synaptic transmission on nonlesioned cultures. Immunostaining carried out by using antibodies directed against neurofilament proteins showed that there was a marked reduction in the number of regenerating fibres crossing the lesion. In contrast to this, chelerythrine (50 microM) did not prevent functional recovery, although it affected synaptic transmission and plasticity at this concentration. We conclude that the inhibition of sprouting produced by staurosporine is independent of its blockade of PKC-mediated phosphorylation mechanisms.

Sprouting and functional recovery in co-cultures between old and young hippocampal organotypic slices

We developed a model of lesion of Schaffer collaterals in hippocampal organotypic slice cultures to analyse the capacity for sprouting and functional recovery expressed in young (one week old) and old (four week old) slice cultures. Slice cultures were sectioned at different ages of maturation in two separate half-slices and maintained in co-culture. Functional recovery was assessed by measuring synaptic responses elicited across the lesion seven days after the lesion and sprouting was evaluated by biocytin labeling of the regenerating fibers seen under the same conditions. Sprouting and functional recovery were found to be markedly reduced and delayed in old vs young cultures. Preparation of co-cultures between young CA3 and old CA1 half-slices resulted in a significant reduction in the capacity for sprouting and regeneration of the young CA3 neurons. Conversely, co-cultures prepared between old CA3 and young CA1 half-slices showed a markedly enhanced capacity for sprouting and functional recovery of old CA3 neurons. These results indicate that the age-dependent impairment in sprouting and regeneration expressed in cortical regions can be improved by and depends upon the presence of a favourable environment.

Sequential Adsorption of Human Serum Albumin (HSA), Immunoglobulin G (IgG), and Fibrinogen (Fgn) at HMDSO Plasma Polymer Surfaces

The sequential adsorption of human serum albumin (HSA), immunoglobulin G (IgG), and fibrinogen (Fgn) at hexamethyldisiloxane (HMDSO) plasma polymer surfaces was investigated with ellipsometry and total internal reflection fluorescence spectroscopy (TIRF) as a function of adsorption time, pH, and excess electrolyte concentration. HSA was found to self-exchange very slowly ( approximately hours) at pH 7.2, irrespective of adsorption time in the range 90 s to 90 min. Preadsorbed HSA was exchanged by Fgn and IgG only to a limited extent irrespectively of pH (5 </= pH </= 8) and excess electrolyte concentration (5 mM </= Cs </= 150 mM). At an excess electrolyte concentration of 150 mM, the sequential adsorption of Fgn and IgG was dramatically reduced by HSA preadsorption, irrespective of pH. At an excess electrolyte concentration of 5 mM, on the other hand, there were indications of second-layer adsorption of Fgn and IgG. Copyright 1997Academic Press

Regulatory phosphorylation of AMPA-type glutamate receptors by CaM-KII during long-term potentiation

Long-term potentiation (LTP), a cellular model of learning and memory, requires calcium-dependent protein kinases. Induction of LTP increased the phosphorus-32 labeling of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type glutamate receptors (AMPA-Rs), which mediate rapid excitatory synaptic transmission. This AMPA-R phosphorylation appeared to be catalyzed by Ca2+- and calmodulin-dependent protein kinase II (CaM-KII): (i) it correlated with the activation and autophosphorylation of CaM-KII, (ii) it was blocked by the CaM-KII inhibitor KN-62, and (iii) its phosphorus-32 peptide map was the same as that of GluR1 coexpressed with activated CaM-KII in HEK-293 cells. This covalent modulation of AMPA-Rs in LTP provides a postsynaptic molecular mechanism for synaptic plasticity.

MLN64 exhibits homology with the steroidogenic acute regulatory protein (STAR) and is over-expressed in human breast carcinomas

The MLN64 gene, which is localized in q12-q21 of the human chromosome 17, encodes a novel protein containing 2 distinct domains. At the N-terminal, MLN64 exhibits a potential trans-membrane region, while at the C-terminal, it shares homology with the F26F4.4 protein of Coenorhabditis elegans and the steroidogenic acute regulatory (StAR) protein, a mitochondrial protein which is involved in steroid-hormone synthesis. By comparing the C-terminal part of these proteins, we defined a novel protein domain, which we termed SHD for "StAR Homology Domain". Of the 93 primary invasive breast carcinomas that were examined, 14 were found to over-express MLN64. These 14 tumors also expressed high c-erbB-2 transcript levels, which were not detected in the MLN64-negative tumors. MLN64 mRNA and protein were specifically detected in malignant cells of breast carcinomas. MLN64 protein was localized within bundle-like structures distributed throughout the cell cytoplasm and condensed in a perinuclear patch, suggesting an association with a specific cell compartment. When the N-terminal part of MLN64 was deleted, MLN64 was uniformly distributed in the cell cytoplasm, indicating that N-terminal part is involved in the specific cytoplasmic localization of MLN64. The homology between the C-terminal part of MLN64 and the functional StAR domain (SHD) suggests that MLN64 and StAR, although distributed in different cellular compartments, may both play a role in steroidogenesis. In this case, the high levels of MLN64 observed in some breast carcinomas could contribute to the progression of these tumors through increased intratumoral steroidogenesis.

MLN64 exhibits homology with the steroidogenic acute regulatory protein (STAR) and is over-expressed in human breast carcinomas

The MLN64 gene, which is localized in q12-q21 of the human chromosome 17, encodes a novel protein containing 2 distinct domains. At the N-terminal, MLN64 exhibits a potential trans-membrane region, while at the C-terminal, it shares homology with the F26F4.4 protein of Coenorhabditis elegans and the steroidogenic acute regulatory (StAR) protein, a mitochondrial protein which is involved in steroid-hormone synthesis. By comparing the C-terminal part of these proteins, we defined a novel protein domain, which we termed SHD for "StAR Homology Domain". Of the 93 primary invasive breast carcinomas that were examined, 14 were found to over-express MLN64. These 14 tumors also expressed high c-erbB-2 transcript levels, which were not detected in the MLN64-negative tumors. MLN64 mRNA and protein were specifically detected in malignant cells of breast carcinomas. MLN64 protein was localized within bundle-like structures distributed throughout the cell cytoplasm and condensed in a perinuclear patch, suggesting an association with a specific cell compartment. When the N-terminal part of MLN64 was deleted, MLN64 was uniformly distributed in the cell cytoplasm, indicating that N-terminal part is involved in the specific cytoplasmic localization of MLN64. The homology between the C-terminal part of MLN64 and the functional StAR domain (SHD) suggests that MLN64 and StAR, although distributed in different cellular compartments, may both play a role in steroidogenesis. In this case, the high levels of MLN64 observed in some breast carcinomas could contribute to the progression of these tumors through increased intratumoral steroidogenesis.

Adsorption of immunoglobulin G and anti-factor VIII inhibitory antibody from haemophiliac plasma to derivatized polystyrenes

Modified polystyrene resins containing sulphonate groups and tyrosyl sulphamide or tyrosyl methyl ester sulphamide groups have been investigated with respect to their potential for selective binding of anti-Factor VIII inhibitory antibodies from plasma. Adsorption of total immunoglobulin G and of a monoclonal antibody to Factor VIII was measured following addition of the radioiodinated proteins to normal plasma, plasma depleted of Factor VIII by adsorption on a resin coupled to anti-Factor VIII antibody, and haemophiliac plasma containing various levels of inhibitory anti-Factor VIII antibody. Depletion of anti-Factor VIII antibody from the haemophiliac plasmas by incubation with the resins was also measured by Bethesda assay. The modified resins and their corresponding unmodified "controls' showed similar binding of total immunoglobulin G. However, only resins containing either sulphonate or a combination of sulphonate and tyrosyl sulphamide groups showed evidence of selective adsorption of anti-Factor VIII antibody from plasma.