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C Weibull

Publications and source records attributed to C Weibull.

At least 19 recordsLinked to original sources
PubMed1993

Crystallization and preliminary X-ray investigation of the Escherichia coli molecular chaperone cpn60 (GroEL).

The Escherichia coli molecular chaperone, cpn60 (GroEL), has been purified from an overproducing E. coli strain and crystallized. Of the two crystal forms that were obtained, one was found to be suitable for crystallographic and structural studies at low resolution. Preliminary X-ray investigation of the crystals show unit cell dimensions: a = 143.3, b = 154.6 and c = 265 A, with alpha = 82 degrees, beta = 95 degrees and gamma = 107 degrees. The space group is P1 and the crystals diffract to a maximum of 7 A when using CuK alpha X-rays from a rotating anode. Both electron microscopy and non-denaturing electrophoretic analysis of redissolved cpn60 crystals show that cpn60 crystallizes in the native oligomeric form. Comparison between the dimensions of oligomeric cpn60 and the crystallographic unit cell volume suggests that the unit cell contains two oligomeric cpn60 molecules. The VM value for two cpn60 molecules per unit cell is 3.5 A3/Da, corresponding to a water content of 65%. Electrophoretic analysis under denaturing conditions shows that the cpn60 in crystals is heterogeneous, and this probably explains the limited resolution of the diffraction data.

Bacterial Proteins↗
PubMed1991

Infectious entry pathway of adenovirus type 2.

Internalization of the infectious fraction of human adenovirus type 2 into HeLa cells was followed by a quantitative internalization assay. Treatments known to selectively block receptor-mediated endocytosis reduced the internalization of infectious virus to an extent close to the reduction of endocytosis of transferrin. This suggests that one of the first steps in the infectious cycle of adenovirus type 2 is internalization by the coated-pit and -vesicle pathway.

Adenoviruses, Human↗
PubMed1990

Physiological and Morphological Changes Induced by Nutrient Limitation of Pseudomonas fluorescens 378 in Continuous Culture.

Pseudomonas fluorescens 378 was studied in continuous culture at a dilution rate of 0.05 or 0.15 h and under a limitation of carbon/energy, nitrogen, phosphorus, iron(III), or oxygen. Cultures were examined for nutritional consumption, production of biosurfactant AP-6 and lipase, and electron microscopy morphology. Morphological features were lysis and plasmolysis of the cells, vacuoles in the cells, granules in cell nuclei, and DNA coagulation during transmission electron microscopy preparation. Biosurfactant and lipase production were lost after 8 to 15 retention times, but under iron limitation and at low dilution rate they were maintained for more than 30 retention times. Consumption of nutrients varied between different cultures. Between 2.4 and 6.0 g of succinic acid per g (dry weight) was consumed; the highest value was obtained under phosphorus limitation. The uptake of nitrogen was mostly about 0.16 g/g (dry weight), and that of phosphorus varied between 13 and 58 mg/g (dry weight). Phosphorus-limited cells reduced their phosphorus consumption by at least 50% compared with other limitations. Cell morphology varied among different cultures. Up to 25% cell lysis occurred at the higher dilution rate. The frequencies of plasmolysis varied between 0 and 85%. Granules in nuclei were found in 65 to 100% of the cells. Vacuoles appeared mostly in low numbers, but at the lower dilution rate under phosphorus or iron limitation the frequencies increased to between 25 and 85%. At high dilution rate, the DNA coagulated in 30 to 70% of the cells. Multivariate data analysis demonstrated a general difference between the two tested dilution rates; i.e., both nutritional and morphological features differed more between the two tested dilution rates than between the different limitations. Cultures at the lower dilution rate changed more with time; this was especially pronounced for phosphorus or iron limitation. The data analysis also showed a correlation between plasmolysis or vacuoles in the cells and an increased carbon uptake under phosphorus limitation.

Journal Article↗
PubMed1986

Extraction of proteins and membrane lipids during low temperature embedding of biological material for electron microscopy.

The extraction of proteins and membrane lipids from biological materials during embedding procedures for electron microscopy carried out at temperatures down to 223 K was studied. Glutaraldehyde-fixed cells of Acholeplasma laidlawii mainly served as test material. More than 99% of the protein and 88% of the lipid of these cells were retained after dehydration with ethanol or acetone between 277 and 223 K and infiltration with methacrylate at 223 K. When methanol was used for dehydration, only 54% of the lipid was retained. The amount of extracted lipid was essentially independent of the ratio between volume of extraction liquid and amount of material subjected to extraction. The cytoplasmic membrane of sectioned Acholeplasma-cells dehydrated and infiltrated as described above appeared more diffuse than that of cells fixed with glutaraldehyde and osmium tetroxide in epoxy resin at room temperature. Glutaraldehyde-fixed erythrocyte ghosts retained 85% of their phospholipid content when dehydrated with ethanol between 277 and 223 K and infiltrated with methacrylate at 223 K. Spinach chloroplasts and thylakoid vesicles retained 61% and 35%, respectively, of their chlorophyll content.

Acholeplasma laidlawii↗
PubMed1984

Extraction of lipids during freeze-substitution of Acholeplasma laidlawii-cells for electron microscopy.

Cells of the bacterium Acholeplasma laidlawii were rapidly frozen against a copper block cooled by liquid helium. The frozen cells were transferred to liquid nitrogen and subsequently to acetone or methanol at 183 K. After 24 h the cells were infiltrated at 203 K with a non-polar methacrylate resin of the same type as Lowicryl HM20. The resin was cured at the same temperature. Acetone extracted approximately 5% of the lipid content of the cells, methanol 15-45% and the resin only negligible amounts. Similar results were obtained with A. laidlawii-ghosts. The cells appeared well preserved when examined in the electron microscope.

Acholeplasma laidlawii↗
PubMed1984

Light and electron microscopic studies of anaerobic curved bacteria isolated from the vagina.

Twenty strains of anaerobic curved rods isolated from vaginal secretion were studied with light and transmission electron microscopy. Ten of the strains were of a short (approx. 1.5 microns) Gram-variable type, while ten were of a long (approx. 3 microns) Gram-negative type. The former had one to four flagella and the latter between one and eight. The flagella originated from the concave aspect of the cells. Thin sections of both types of bacteria revealed an approximately 30 nm thick cell wall with no outer membrane, similar to that of most Gram-positive bacteria. An electron-dense zone in the middle of the cell wall, atypical of Gram-positive bacteria, was found, however. Amorphous and electron-translucent cytoplasmic inclusions, not membrane-enclosed, were detected. These inclusions stained metachromatically with Albert's stain.

Bacteria, Anaerobic↗
PubMed1979

Fractionation of membranes from Acholeplasma laidlawii A on the basis of their surface properties by partition in two-polymer aqueous phase systems.

Acholeplasma laidlawii A consists of pleomorphic cell clusters surrounded by a single membrane. When lysed, a cell gives rise to several membrane fragments which cannot be separated from each other by isopycnic sucrose gradient centrifugation. A heterogeneous lateral organization of the cell membranes was detected by countercurrent distribution of membrane fragments in a two-polymer aqueous phase system. It revealed that the membranes consist of at least two subpopulations with respect to surface properties. Changes in the fatty acid and cholesterol content of the membranes revealed that the resolution of different subpopulations was predominantly due to a critical ratio of monoglucosyldiglyceride to diglucosyldiglyceride. The heterogeneity of the membrane probably depends on lipid-lipid and lipid-protein steric interactions. Charged lipids, an apolar monoglucolipid and the ratio between lipids and proteins also affect membrane partition. The differences in the subpopulations were further reflected by different specific activities of NADH dehydrogenase, NADH oxidase and ATPase. These activities varied independently. Minor quantitative differences in the protein patterns of different subpopulations were apparent. The origin and the preservation of the membrane subpopulations are discussed in terms of lipid-lipid and lipid-protein interactions, their age and energy metabolism.

Acholeplasma laidlawii↗
PubMed1978

Comparison of light and electron microscopic determinations of the number of bacteria and algae in lake water.

Determinations of the number of microorganisms in lake water samples with the bright-field light microscope were performed using conventional counting chambers. Determinations with the fluorescence microscope were carried out after staining the organisms with acridine orange and filtering them onto Nuclepore filters. For transmission electron microscopy, a water sample was concentrated by centrifugation. The pellet was solidifed in agar, fixed, dehydrated, embedded in Epon, and cut into thin sections. The number and area of organism profiles per unit area of the sections were determined. The number of organisms per unit volume of the pellet was then calculated using stereological formulae. The corresponding number in the lake water was obtained from the ratio of volume of solidified pellet/volume of water sample. Control experiments with pure cultures of bacteria and algae showed good agreement between light and electron microscopic counts. This was also true for most lake water samples, but the electron microscopic preparations from some samples contained small vibrio-like bodies and ill-defined structures that made a precise comparison more difficult. Bacteria and small blue-green and green algae could not always be differentiated with the light microscope, but this was easily done by electron microscopy. Our results show that transmission electron microscopy can be used for checking light microscopic counts of microorganisms in lake water.

Journal Article↗
PubMed1975

Ultrastructure of Lactobacillus fermentum during early and late growth phases and during thiamine deficiency.

Thin sections of exponentially growing and stationary-phase cells of L. fermentum from thiamine sufficient and thiamine deficient media were studied by electron microscopy. Compared to the exponential-phase cells the stationary-phase cells from both types of media had thicker cell walls and cross walls and fewer and smaller granules of storage material. Exponential-phase, thiamine deficient cells had rather thin cell walls and small mesosomes.

Cell Membrane↗