Growth of collagen fibrils produced by human osteosarcoma cells: high-resolution scanning electron microscopy. (1/206)

To demonstrate three-dimensionally the process of the collagen fibril growth, the bottom of culture dishes with human osteosarcoma cells (NOS-1) and their extracts were examined by conventional scanning electron microscopy (SEM). Backscattered electron (BSE) imaging of SEM was also applied to the specimens, which were stained with phosphotungustic acid and uranyl acetate. Conventional SEM images showed several stages of collagen fibril assembly. Short collagen fibrils with tapered ends were distributed at the bottom of the dish just beneath and/or around the cultured cells; they were 1 microm long and 20-30 nm in diameter at the thickest middle portion. These fibrils were often twisted and united in a right helical direction, and consequently increased in length (5-10 microm) and diameter (more than 100 nm). In BSE images, the periodical bands stained with phosphotungstic acid and uranyl acetate were visualized throughout the individual fibrils. The banding pattern indicated that the polarity of the collagen molecules was unidirectional; namely, that all molecules were pointed in the same direction throughout the length of the fibrils.  (+info)

Analytical and clinical evaluation of two homogeneous assays for LDL-cholesterol in hyperlipidemic patients. (2/206)

BACKGROUND: LDL-cholesterol (LDL-C) concentrations are the primary basis for treatment guidelines established for hyperlipidemic patients. LDL-C concentrations are commonly monitored by means of the Friedewald formula, which provides a relative estimation of LDL-C concentration when the triglyceride concentration is <2000 mg/L and there are no abnormal lipids. The Friedewald formula has several limitations and may not meet the current total error requirement of <12% in LDL-C measurements. METHODS: We evaluated the analytical and clinical performance of two direct methods (Roche and Wako) by analyzing 313 fresh serum samples obtained from dyslipidemic patients in a lipid clinic and comparing them with modified beta-quantification. RESULTS: Both homogeneous assays displayed excellent precision (CV <2%). The Roche method showed a mean total error of 7.72%, and the Wako method showed a mean total error of 4.46% over a wide range of LDL-C concentrations. The Roche method correlated highly with the modified beta-quantification assay (r = 0.929; y = 1.052x - 168 mg/L; n = 166) and showed a bias of -4. 5% as a result of the assigned standard value. The Wako method also correlated highly with beta-quantification (r = 0.966; y = 0.9125x + 104.8 mg/L; n = 145) without significant bias. The Roche method correctly classified 97% of patients with triglycerides <2000 mg/L, 75% of patients with type IIb hyperlipemia (HPL), and 84% of patients with type IV HPL based on the cutpoints of 1300 and 1600 mg/L, compared with 98%, 78.4%, and 89%, respectively, for the Wako method. In dysbetalipoproteinemic patients, both methods have a 30% mean positive bias compared with beta-quantification. CONCLUSIONS: Both direct methods can be a useful alternative when ultracentrifugation is not available for the diagnosis and control of lipid-lowering medication for patients with mixed HPL, but not for patients with type III hyperlipidemia.  (+info)

Fine structure of lipid-depleted mitochondria. (3/206)

The fine structure of mitochondria and submitochondrial vesicles depleted of their lipid by extraction with aqueous acetone was studied. Thin sections of mitochondrial membranes depleted of more than 95% of their lipid retained the unit membrane structure. Densitometer tracings of the electron micrographs showed that the unit membrane of extracted mitochondria was, on the average, wider than that of unextracted controls and showed a greater variation in width. The outer membrane was lost in mitochondria from which 80-95% of the lipids was extracted. Inner membrane particles were present on submitochondrial vesicles depleted of up to 85% of their lipids. However, when more than 95% of the lipid was removed, few, if any, particles remained attached to the membranes but many particles were found unattached in the background. When lipid was restored to lipid-deficient preparations, the mitochondrial membranes were found to be devoid of inner membrane particles but were fully active with respect to succinate-cytochrome c reductase activity.  (+info)

Octagonal nuclear pores. (4/206)

Negative staining of isolated nuclear envelopes by phosphotungstate shows that the nuclear pores are octagonal rather than circular. Pores of the same shape and approximately the same width, 663 +/- 5 A, were demonstrated in the newt, Triturus, the frog, Rana, and the starfish, Henricia. The outer and inner diameters of the annulus associated with each pore are respectively greater and less than the width of the pore itself. For this reason surface views of the envelope, unless negatively stained, fail to show the true dimensions of the pores.  (+info)

Novel filaments 5 nm in diameter constitute the cytosolic ring of the plastid division apparatus. (5/206)

The plastid division apparatus (called the plastid-dividing ring) has been detected in several plant and algal species at the constricted region of plastids by transmission electron microscopy. The apparatus is composed of two or three rings: an outer ring in the cytosol, an inner ring in the stroma, and a middle ring in the intermembrane space. The components of these rings are not clear. FtsZ, which forms the bacterial cytokinetic ring, has been proposed as a component of both the inner and outer rings. Here, we present the ultrastructure of the outer ring at high resolution. To visualize the outer ring by negative staining, we isolated dividing chloroplasts from a synchronized culture of a red alga, Cyanidioschyzon merolae, and lysed them with nonionic detergent Nonidet P-40. Nonidet P-40 extracted primarily stroma, thylakoids, and the inner and middle rings, leaving the envelope and outer ring largely intact. Negative staining revealed that the outer ring consists of a bundle of 5-nm filaments in which globular proteins are spaced 4.8 nm apart. Immunoblotting using an FtsZ-specific antibody failed to show immunoreactivity in the fraction containing the filament. Moreover, the filament structure and properties are unlike those of known cytoskeletal filaments. The bundle of filaments forms a very rigid structure and does not disassemble in 2 M urea. We also identified a dividing phase-specific 56-kD protein of chloroplasts as a candidate component of the ring. Our results suggest that the main architecture of the outer ring did not descend from cyanobacteria during the course of endosymbiosis but was added by the host cell early in plant evolution.  (+info)

Protein aggregation after focal brain ischemia and reperfusion. (6/206)

Two hours of transient focal brain ischemia causes acute neuronal death in the striatal core region and a somewhat more delayed type of neuronal death in neocortex. The objective of the current study was to investigate protein aggregation and neuronal death after focal brain ischemia in rats. Brain ischemia was induced by 2 hours of middle cerebral artery occlusion. Protein aggregation was analyzed by electron microscopy, laser-scanning confocal microscopy, and Western blotting. Two hours of focal brain ischemia induced protein aggregation in ischemic neocortical neurons at 1 hour of reperfusion, and protein aggregation persisted until neuronal death at 24 hours of reperfusion. Protein aggregates were found in the neuronal soma, dendrites, and axons, and they were associated with intracellular membranous structures during the postischemic phase. High-resolution confocal microscopy showed that clumped protein aggregates surrounding nuclei and along dendrites were formed after brain ischemia. On Western blots, ubiquitinated proteins (ubi-proteins) were dramatically increased in neocortical tissues in the postischemic phase. The ubi-proteins were Triton-insoluble, indicating that they might be irreversibly aggregated. The formation of ubi-protein aggregates after ischemia correlated well with the observed decrease in free ubiquitin and neuronal death. The authors concluded that proteins are severely damaged and aggregated in neurons after focal ischemia. The authors propose that protein damage or aggregation may contribute to ischemic neuronal death.  (+info)

Colorimetric, enzymatic, and liquid-chromatographic methods for serum uric acid compared. (7/206)

We describe high-performance liquid chromatography in conjunction with electrochemical detection as a possible reference method for serum uric acid. Separation was effected on a column packed with "Vydac" strong anion-exchange resin, with use of a detection potential of +0.80 V vs. an Ag/AgCl reference electrode. Results were linearly related to concentration up to 1.0 g/liter, and no interferences were seen. Assay of human sera gave within-run and day-to-day coefficients of variation of 0.83% and 1.1%, respectively; analytical recoveries averaged 100%. Comparison of the new procedure (x) with the phosphotungstate and uricase methods (y) showed the following linear regression and correlation coefficients for results: y equal 0.963x + 0.219 (r = 0.995), and y = 0.991x + 0.165 (r = 0.999), respectively. As compared to these methods, the procedure we describe is more accurate, because of the selective detection system based on retention time and redox potential. Samples can be analyzed at the rate of 20/h. No deproteinization is required.  (+info)

A morphological study of the internal component of influenza virus. (8/206)

Rapid treatment of influenza virus directly on the microscope grid with non-ionic detergent had allowed better visualization of the internal component. Many micrographs show that this ribonucleoprotein (RNP) is present as a continuous stand of 6 nm diam. arranged in the form of a double coil or helix. In spite of the minimal treatment to which the virus was subjected most helices still showed signs of degradation. The findings that we have obtained lead us to suggest that the RNP component of influenza virus must be very sensitive to both chemical and physical manipulations, any of which could cause it to fracture from one continuous strand into several pieces, although such breakages could possibly occur at specific points along its length.  (+info)