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At least 253 records · Page 14Linked to original sources
PubMed2003

Non-particulate (continuous bed or monolithic) restricted-access reversed-phase media for sample clean-up and separation by capillary-format liquid chromatography.

Restricted-access reversed-phase non-particulate (continuous bed or monolithic) stationary phases of different hydrophobicity synthesized in 100 microm i.d. fused silica capillaries have been evaluated. A specific property of restricted-access media (RAM) is that they interact with small analytes and exclude big molecules, e.g. proteins, from access to the active sites and adsorption on the surface. This dual property facilitates direct injection of biological fluids for drug or drug-metabolite analysis. Different RAM and RAM-precursor capillary columns were tested to assess the influence of chromatographic bed morphology on loadability. Inverse size-exclusion chromatography was used for investigation of pore structural properties of the capillary-format continuous beds. The data obtained were used to discuss the mechanism of separation of the biological samples using capillary columns and to propose a model for the topochemical architecture of the RAM investigated. Different morphology of the non-particulate reversed-phase precursors resulted in two types of RAM material shielded with hydrophilic polymer, classified as homogeneous or heterogeneous topochemistry stationary phases. Capillary columns were applied for chromatography of biological fluids. High resolution was obtained, without the need for column switching, when capillary columns operated in gradient conditions. Extensive evaluation of the chromatographic properties (hydrophobicity, efficiency, separation impedance, and loadability) of the non-particulate reversed-phase materials was performed before and after shielding with hydrophilic polymer to generate restricted-access properties. Minor changes of hydrophobicity, efficiency, or separation impedance were observed after the shielding.

Acetaminophen↗
PubMed2005

Particle picking by segmentation: a comparative study with SPIDER-based manual particle picking.

Boxing hundreds of thousands of particles in low-dose electron micrographs is one of the major bottle-necks in advancing toward achieving atomic resolution reconstructions of biological macromolecules. We have shown that a combination of pre-processing operations and segmentation can be used as an effective, automatic tool for identifying and boxing single-particle images. This paper provides a brief description of how this method has been applied to a large data set of micrographs of ice-embedded ribosomes, including a comparative analysis of the efficiency of the method. Some results on processing micrographs of tripeptidyl peptidase II particles are also shown. In both cases, we have achieved our goal of selecting at least 80% of the particles that an expert would select with less than 10% false positives.

Algorithms↗
PubMed2005

[Pituitary and ovarian mass syndrome in primary hypothyroidism].

INTRODUCTION: Hyperprolactinemia and a pituitary mass syndrome can occur in patient with primary hypoyhroidism. In young women, hypothyroidism can be associated with ovarian cysts. EXEGESIS: We report a case of a 30 year-old women who was treated for an anemia. She had clinical and biological signs of primary hypothyroidism with hyperprolactinemia at the biology. Pituitary MRI showed a pituitary mass. The pelvic ultrasound examination and CT scan showed a right ovarian cyst. The subsequent thyroid hormone replacement was associated with a clinical, a biological and radiological resolution. It was a pituitary and ovarian mass syndrome secondary to primary hypothyroidism. CONCLUSION: The recognition of these associations may eliminate unnecessary surgery and lead to the choice of hormone replacement therapy.

Adult↗
PubMed2002

Determination of olanzapine in human blood by liquid chromatography-tandem mass spectrometry.

A liquid chromatographic-tandem mass spectrometric (LC-MS-MS) assay was developed and validated to quantitatively determine olanzapine (OLZ) concentrations in human blood. Liquid-liquid extraction, using n-butanol:cyclohexane (3:47, v/v), was used to isolate OLZ and its internal standard, LY170158, from the biological matrix. Chromatographic resolution of OLZ from endogenous interferences and known metabolites was accomplished with a MetaChem Monochrom HPLC column (4.6 x 150 mm, d(p) 5 microm). Detection occurred using a Perkin-Elmer Sciex API III Plus triple quadrupole mass spectrometer using positive ion APCI and multiple reaction monitoring (MRM). The linear dynamic range was from 5 to 500 ng ml(-1) based on a 0.25-ml aliquot of human blood. The inter-day precision (%RSD) and accuracy (%RE) ranged from 3.65 to 10.64 and from -2.14 to 3.07, respectively. Modifications to an existing assay for the determination of OLZ in human plasma were necessary. A different structural analog was used as the internal standard due to instability observed for the original analog when using human blood as the matrix. A second modification was the addition of the anti-oxidant sodium ascorbate to inhibit degradation of OLZ in human blood, as has been noted by other investigators. Upon fortification of human blood with sodium ascorbate (final concentration, 0.33 mM), OLZ was found to be stable for at least 1 week at -70 degrees C as well as through two freeze-thaw cycles. This assay, which will be used to investigate the distribution of OLZ in human blood, grants insight into the proper sample handling conditions needed to perform valid determinations of OLZ in human blood.

Antipsychotic Agents↗
PubMed2002

Tutorial on off-axis electron holography.

Through recent years, off-axis electron holography has helped us to understand and to overcome some experimental restrictions in transmission electron microscopy. With development of powerful electron microscopes, slow-scan CCD cameras, and computers, holography is not an academic technique anymore used by specialized laboratories. Holography has proven its wide range of applications in solving real-world problems in materials science and biology. At medium resolution, that is, on nanometer scale, holography allows access to large area phase contrast produced by magnetic fields and electric potentials. In the high-resolution domain, holography unveils its power by unscrambling amplitude and phase of the electron wave, resulting in an improved lateral resolution up to the information limit. Holography is a thoroughly quantitative method, and, in combination with the perfect zero-loss filtering inherent to this method, the interpretation of the reconstructed data is strongly simplified. After outlining the basics of holography, in this tutorial we focus on development of a step-by-step procedure for recording and reconstruction of holograms. At the end, some recent applications are discussed.

Holography↗
PubMed2003

A novel light source for SICM-SNOM of living cells.

We have developed a novel light source for use in a scanning near-field optical microscope (SNOM or NSOM) based on a nanopipette whose distance from the sample surface is controlled using scanning ion conductance microscopy. The light source is based on the general principle of the chemical reaction between a fluorophore in the pipette and ligand in the bath, to produce a highly fluorescent complex that is continually renewed at the pipette tip. In these experiments we used fluo-3 and calcium, respectively. This complex is then excited with an Ar+ laser, focused on the pipette tip, to produce the light source. This method overcomes the transmission problem of more traditional SNOM probes and has been used to acquire simultaneous high-resolution topographic and optical images of biological samples in physiological buffer. A resolution of approximately 220 nm topographic and approximately 190 nm optical was determined through imaging fixed sea-urchin sperm flagella. Live A6 cells were also imaged, demonstrating the potential of this system for SNOM imaging of living cells.

Aniline Compounds↗
PubMed1989

Distances as degrees of freedom.

Tertiary contact distance information of varying resolution for large biological molecules abounds in the literature. The results provided herein develop a framework by which information of this type can be used to reduce the allowable configuration space of a macromolecule. The approach combines graph theory and distance geometry. Large molecules are represented as simple, undirected graphs, with atoms, or groups, as vertices, and distances between them as edges. It is shown that determination of the exact structure of a molecule in three dimensions only requires the specification of all the distances in a single tetrahedron, and four distances to every other atom. This is 4N-10 distances which is a subset of the total N(N-1)/2 unique distances in a molecule consisting of N atoms. This requirement for only 4N-10 distances has serious implications for distance geometry implementations in which all N(N-1)/2 distances are specified by bounded random numbers. Such distance matrices represent overspecified systems which when solved lead to non-obvious distribution of any error caused by inherent contradictions in the input data. It is also shown that numerous valid subsets of 4N-10 distances can be constructed. It is thus possible to tailor a subset of distances using all known distances as degrees of freedom, and thereby reduce the configuration space of the molecule. Simple algebraic relationships are derived that relate sets of distances, and complicated rotations are avoided. These relationships are used to construct minimum, complete sets of distances necessary to specify the exact structure of the entire molecule in three dimensions from incomplete distance information, and to identify sets of inconsistent distances. The method is illustrated for the flexible structural types present in large ribosomal RNAs: 1.) A five-membered ring; 2.) a chemically bonded chain with its ends in contact (i.e., a hairpin loop); 3.) the spatial orientation of two separate molecules, and; 4.) an RNA helix that can have variation in individual base pairs, giving rise to global deviation from standardized helical forms.

Base Composition↗
PubMed1992

Acquired type II von Willebrand's disease associated with adrenal cortical carcinoma.

A case of acquired von Willebrand's disease (AvWD) associated with an adrenal cortical carcinoma is reported. The circulating highest molecular weight multimers (HMWM) of von Willebrand factor (vWF) were decreased when assessed by SDS-agarose plasma electrophoresis, leading to the diagnosis of type II AvWD. No forms of inhibitor could be detected in the plasma of the patient. In contrast, indirect immunoperoxidase studies with a monoclonal antibody to vWF demonstrated an absorption of vWF into malignant cells. Infusion of a vWF-FVIII concentrate, containing significant amounts of HMWM of vWF, allowed surgical resection of the tumour. After the first infusion of the concentrate, the vWF-RCo recovery was found to be low (38%) compared to the vWF:Ag (75%) and FVIII:C (163%) recoveries. The resolution of all biological signs of vWD, including the abnormal multimeric pattern, in the post-operative period was prompt and permanent. Therefore, the absorption of the HMWM of vWF by carcinomatous cells appears to represent a likely pathophysiological mechanism responsible for the AvWD syndrome in this patient.

Adrenal Gland Neoplasms↗
PubMed1985

Cryo-electron microscopy of helical particles TMV and T4 polyheads.

Vitrified Tobacco Mosaic Virus (TMV) and T4 polyhead suspensions have been studied by cryo-electron microscopy. The order of TMV particles is preserved to distances better than 0.3 nm when vitrified. In spite of the high beam sensitivity of unstained biological material, the resolution of images extends to 1.15 nm. Radial density distributions calculated from images of TMV and the helical aggregate of TMV protein (TMVP) show that the RNA is likely visualized in the virus. However, due to the imaging conditions of unstained vitrified specimens, the position of the RNA is erroneous. While TMV and TMVP do not show any departure from cylindrical symmetry, T4 polyheads are sensitive to the thickness of the ice layer in which they are embedded. To avoid flattening, T4 polyheads have to be embedded in an ice layer thicker than their diameter.

Freezing↗
PubMed1978

Concurrent grandparent death and birth of schizophrenic offspring: an intriguing finding.

The finding, in the following study, of grandparent death within +/- two years of birth of 41 per cent of schizophrenics (N = 70), a rate significantly higher than that in psychiatric (N = 45) and normal (N = 25) control groups, raises the possibility that this family stress factor may contribute to the development of schizophrenia. The implications are considered regarding the likelihood that the concurrent stresses of the death and the birth, two major events in the family life cycle, could confound and impede mourning and parenting processes. Two hypotheses are suggested: (a) that a bereaved parent may be emotionally unavailable to spouse and infant, and (b) that attention to the child may block mourning and absorb painful feelings, with the child assuming a special replacement role. The dysfunctional potential is related to other interacting variables, including biological factors, mourning resolution, and the family system. Further study is called for.

Adolescent↗
PubMed2006

Diastereoselective synthesis of some novel benzopyranopyridine derivatives.

BACKGROUND: The formation of novel N-substituted-1,2,3,4-tetrahydro[1,3]-dioxolo-[6,7]-5H-[1]benzopyrano [3,4-c]pyridines were observed unexpectedly during the acid-mediated ketal removal of ethylenedioxy ketal protected 4-piperidones. The literature revealed that benzopyranopyridine derivatives are of scientific interest and some exhibit interesting biological activities. Diastereomeric resolution was utilized to isolate optically pure chiral molecules. RESULTS: The acid catalyzed deprotection of N-substituted-4,4-ethylenedioxy-3- [(1,3-benzodioxol-5-yloxy)methyl]piperidines, prepared by condensation of the corresponding phenols and mesylate derivatives, unexpectedly resulted in cyclodehydration leading to new benzopyrano derivatives, N-substituted-1,2,3,4-tetrahydro[1,3]-dioxolo-[6,7]-5H-[1]benzopyrano [3,4-c]pyridines. The process involves the deprotection of the carbonyl protecting group, and then the cyclization reaction occurs followed by dehydration to give the final product.These N-substituted-1,2,3,4-tetrahydro[1,3]-dioxolo-[6,7]-5H-[1]benzopyrano [3,4-c] pyridines were dealkylated giving the corresponding N-unsubstituted derivatives. The cis-1,3,4,4a,5,10b-hexahydro-[6,7]-2H-[1]benzopyrano [3,4-c]pyridine derivative was also obtained from the N-benzylated-1,2,3,4-tetrahydro[1,3]-dioxolo-[6,7]-5H-[1]benzopyrano [3,4-c]pyridine via catalytic hydrogenation. The resolution of the enantiomers was carried out using D-(-)-mandelic acid as chiral reagent. The absolute configuration of the S,S-mandelate salt derivative was determined by X-ray crystallographic analysis. CONCLUSION: The approach led to the construction of N-substituted-1,2,3,4-tetrahydro[1,3]-dioxolo-[6,7]-5H-[1]benzopyrano [3,4-c] pyridines ring systems involving the one-pot deprotection, cyclization and dehydration of N-substituted-4,4-ethylenedioxy-3- [(1,3-benzodioxol-5-yloxy)methyl]piperidines. The hydrogenation of the N-benzylated benzopyrano [3,4-c]pyridine derivative followed by resolution led to the formation of a new compound.

Journal Article↗
PubMed2002

Molecular views and measurements of hemostatic processes using atomic force microscopy.

Hemostasis and thrombosis are highly complex and coordinated interfacial responses to vascular injury. In recent years, atomic force microscopy (AFM) has proven to be a very useful approach for studying hemostatic processes under near physiologic conditions. In this report, we review recent progress in the use of AFM for studying hemostatic processes, including molecular level visualization of plasma proteins, protein aggregation and multimer assembly, and structural and morphological details of vascular cells under aqueous conditions. AFM offers opportunities for visualizing surface-dependent molecular and cellular interactions in three dimensions on a nanoscale and for sensitive, picoNewton level, measurements of intermolecular forces. AFM has been used to obtain molecular and sub-molecular, resolution of many biological molecules and assemblies, including coagulation proteins and cell surfaces. Surface-dependent molecular processes including protein adsorption, conformational changes, and subsequent interactions with cellular components have been described. This review outlines the basic principles and utility of AFM for imaging and force measurements, and offers objective perspectives on both the advantages and disadvantages. We focus primarily on molecular level events related to hemostasis and thrombosis, particularly coagulation proteins, and blood platelets, but also explore the use of AFM in force measurements and surface property mapping.

Adsorption↗
PubMed1992

Cytogenetic assays for genotoxic agents.

The induction of genetic damage has clear and dramatic implications for human health, with teratogenic, mutagenic, cataractogenic and carcinogenic consequences resulting from cellular chromosomal alterations in appropriate tissues. When analysing the potential of an agent to initiate genetic damage or in evaluating possible incumbent genomic damage a variety of complementary assays may be employed. These apply to cells in vitro, to in vivo assessments involving small mammals and most importantly to derived human cells and tissues including those of ocular origin. Cytogenetic assays have the important advantage that they enumerate damage at the level of the individual cell. Assays involving the examination of chromosomal aberrations at mitosis, of cells prior to mitosis using the technique of premature chromosome condensation, of micronuclei in post-mitotic cells and of sister chromatid exchanges will be described. The development of human chromosome specific probes and fluorescent in situ hybridisation (FISH) techniques combine the resolution of molecular biology with classical cytogenetics in a powerful approach to defining genomic change and its consequences. These techniques and assays can be further augmented by in situ cytometry such that overall a number of parameters can be quantified involving cellular kinetics, clastogen and/or aneugen definition and ultimately the establishment of dose response relationships. A rational basis for avoidance or control, for intervention or for defining probable cause of the role of genotoxicants in the development of human disease can then be established.

Animals↗
PubMed2006

A transmission electron microscopy study on effects of a modified Glutaraldehyde fixation on Acanthamoeba castellanii.

Transmission electron microscopy (TEM) can provide high resolution imaging of biological specimens. The study is to establish the effects of a modified glutaraldehyde (GA) compare to the standard GA fixation on Acanthamoeba castellanii from TEM perspectives and thus provide precise and accurate information on the ultrastructure studies of the parasite. By increasing the contrast, the ultrastructures of the parasite were more evident. The TEM images were obtained from parasites fixed with the modified GA and the standard GA and then the area of the nucleus and the gray values of the image of the nucleus of the parasites were measured. The mean areas of the nucleus were found to be significantly reduced in the standard GA fixed parasites (12210.4 nm2) compared to the modified GA fixed parasites (8676.3 nm2) (p < 0.05). The mean gray values of the image were significantly reduced from 2024 in the standard GA fixed parasites (2024) to the modified GA fixed parasites (1636) (p < 0.05). The study shows that the modified GA produced significantly better contrast on TEM images of the A. castellanii compared to the standard GA. This was because the modified GA generated more free water molecules during fixation and the uptake of modified GA by the nucleus of the parasite organizing all protein constituents in the cell into a more closely packed configuration than that of the standard GA. With such properties, the modified GA is a better fixative providing better images for ultrastructures of the parasite.

Acanthamoeba castellanii↗
PubMed1988

Retrospective DNA analysis by rapid high resolution cytometry in cases with cervical cancer before and after radiotherapy.

DNA analyses of nuclei of squamous cells on 86 cases with squamous cells carcinoma of the uterine cervix, who had been treated with radiotherapy, were studied in 95 specimens. Forty-three specimens taken from invasive cancer cases before radiotherapy and 52 smears taken from the patients with cervical cancer after radiotherapy were examined by rapid high-resolution cytometry. The biologic behavior in this retrospective study was known, and the cases were classified into "poor" and "good" prognostic groups depending on their five year survival rates. In the poor prognostic group, the smears taken prior to radiotherapy showed a significantly lower 5N-exceeding rate (5NER) and a smaller Nuclear area than did those of the good prognostic group. The smears taken from the cases of recurrent cancer and postradiation dysplasia with poor prognosis showed significantly lower 5NER and a smaller Nuclear area than did those from cases of postradiation dysplasia and radiation changes in patients with a good prognosis after radiotherapy.

Adult↗
PubMed1983

[Use of methods of 2-dimensional electrophoresis in population genetics].

The review of literature on application of the methods of two-dimensional electrophoresis according to O'Farrel, in population genetics and in some adjacent fields of biology, is presented. Resolution capacities of both conventional and two-dimensional electrophoresis are briefly characterized. Data on application of two-dimensional electrophoresis methods for evaluation the degree of inter- and intraspecific variability, for detection and characterization of mutations, as well as for analysis of molecular mechanisms of inborn pathology are reviewed.

Alleles↗
PubMed1993

[High resolution autoradiographic detection of beta-gamma emitters in biological tissues: case of Indium 111].

The present paper proposes an efficient autoradiographic procedure for the microscopic localisation in biological tissues of both low energy electrons and electrons released at relatively high energy. These are emitted by radioactive tracers, decaying by electron capture and/or internal conversion, that are increasingly used in biology and medicine. A detailed inventory of the corpuscular and electromagnetic radiations has been established in the specific case of Indium-111, with emphasis placed on those presenting an autoradiographic interest. As far as the electromagnetic component is concerned, the probability for producing secondary electrons as a function of distance from the source has been calculated. The range of the electrons in the emulsion and in a tissue-like medium has also been taken into account. The comparison with experiments using isolated lymphocytes labelled with 111In-oxine confirms the feasibility to localize and quantify with a high resolution beta-gamma emitters within biological systems by autoradiographic imaging.

Autoradiography↗