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Biomedical subjects

F P Ottensmeyer

Publications and source records attributed to F P Ottensmeyer.

At least 19 recordsLinked to original sources
PubMed1991

Vectorial sequence of mineralization in the turkey leg tendon determined by electron microscopic imaging.

Turkey leg tendons were used as a model tissue to study the spatial and temporal relationships of mineral deposition between matrix vesicles and collagen fibrils by various electron microscopic techniques--bright field, selected-area dark field (SADF), and electron spectroscopic imaging (ESI). These latter imaging techniques enabled the direct localization and spatial distributions of both apatite crystals and atomic elements (Ca, P) within matrix vesicles and collagen. In longitudinal planes of section, a consistent vectorial gradient of mineralization was observed which started with the first localization of apatite mineral in matrix vesicles; with further development, the mineral spread from the vesicle to the extravesicular interstices and then into the adjacent collagen fibrils. Once intrafibrillar, the mineral was observed to advance both laterally and axially. The association of vesicle/collagen mineral was examined by ESI analysis of Ca and P elemental maps and appeared as a continuum between the vesicles and the adjacent collagen fibrils. Similarly, an intimate spatial relationship was observed between the mineral of vesicles and collagen in transversely cut sections of tendon. The sequential development of this mineralized matrix is discussed in light of matrix vesicle/collagen interactions.

Animals↗
PubMed1990

Experimental ionization cross-sections of phosphorus and calcium by electron spectroscopic imaging.

The absolute partial electron scattering cross-section for the phosphorus L2,3-shell ionization was measured by electron spectroscopic imaging using poliovirus as a primary standard. The equivalent calcium cross-section was obtained in relation to phosphorus using the stoichiometric ratio for these two elements in hydroxyapatite, Ca10(PO4)6(OH)2. At 80 keV, the partial cross-section of phosphorus was 2.26 x 10(-20) and 2.68 x 10(-20) cm2/atom for poliovirus and hydroxyapatite, respectively, at 150 eV loss for a 15-eV energy window and an acceptance angle of 15 mrad. Under the same conditions the calcium cross-section was 0.49 x 10(-20) cm2/atom at 360 eV loss. The experimental values are slightly higher than the theoretical cross-sections calculated either by hydrogenic or Hartree-Slater approaches.

Calcium↗
PubMed1988

An electron microscopic and spectroscopic study of murine epiphyseal cartilage: analysis of fine structure and matrix vesicles preserved by slam freezing and freeze substitution.

Newborn mice epiphyseal growth plates were preserved by slam freezing/freeze substitution and examined by conventional electron microscopy, stereopsis, high voltage electron microscopy, and electron spectroscopic imaging (ESI). To illustrate the improved ultrastructure of this cryogenic procedure, conventional, aqueously fixed growth plates were included showing collapsed hypertrophic chondrocytes surrounded by a depleted and condensed extracellular matrix. In contrast, the cryogenically prepared epiphyses contain chondrocytes and extracellular matrix vesicles both in direct contact with proteoglycan filaments retained in an expanded state. ESI is an electron microscopic technique which enables the direct localization of atomic elements superimposed over fine structural details. This technique was used to examine the colocalization of calcium and phosphorus within matrix vesicles and within their associated extracellular environments. Matrix vesicles appeared in three distinct diameter ranges. The integrity of the matrix vesicles was examined at various stages of mineralization and also within the mineralized zone of provisional calcification.

Animals↗
PubMed1988

Maximum entropy methods in dark field electron micrographs and elemental maps.

A maximum entropy algorithm is described which not only fits a model to the data consistent with the size of the noise and the maximum entropy principle but also distributes the residuals between the data and the model in a way consistent with the noise in the data having been generated by a random gaussian process. The results of applying the algorithm to profiles of electron micrographs, electron micrographs and model data is presented. The algorithm is found to achieve various degrees of signal to noise ratio enhancement. Preliminary results show that the spatial resolution is not suppressed. A biassing artifact is described.

Algorithms↗
PubMed1987

Evidence for an extended 7SL RNA structure in the signal recognition particle.

The signal recognition particle (SRP) functions in conjunction with the SRP receptor to target nascent ectoplasmic proteins to the protein translocation machinery of the endoplasmic reticulum membrane. SRP is a ribonucleoprotein consisting of six distinct polypeptides and one molecule of 7SL RNA 300 nucleotides long. SRP has previously been visualized by a variety of electron microscopic techniques as a rod-shaped particle 24 nm long and 6 nm wide. We report here microanalysis by electron spectroscopic imaging which localizes the RNA molecule in SRP to primarily the two ends of the particle. These results suggest that the single 7SL RNA molecule spans the length of the particle. Micrographs from a scanning transmission electron microscope permit visualization of unstained SRP with low electron exposure, as well as the direct measurement of the mol. wt of the particle. These micrographs confirm our earlier suggestion that SRP is divided into three structural domains and allow discrimination of the two ends of the structure. The results of both techniques have been combined in a model for the structure of SRP in which we propose the basic orientation of the 7SL RNA. The structure proposed is consistent with the secondary structure predicted for the RNA and with biochemical data.

Microscopy, Electron↗
PubMed1986

Automatic selection of molecular images from dark field electron micrographs.

A method is described which can be used objectively to select putative molecular images from dark field electron micrographs of unstained molecules. The only characteristic of the molecule required for automatic selection is an estimate of molecular weight. Structures are selected from micrographs by a series of steps including: low pass filtering, edge detection and mass determination. The procedure is shown to be reliable for images with signal-to-noise ratios of at least 4.0. Moreover, the method is insensitive to both the shape and the number of molecules in the image. Five different molecules with molecular weights between MW 330,000 and MW 4000 are successfully selected from low dose STEM and high dose tilt beam dark field electron micrographs.

Catalase↗
PubMed1985

Structure of the signal recognition particle by electron microscopy.

The signal recognition particle (SRP) is a ribonucleoprotein consisting of six distinct polypeptide components and one molecule of small cytoplasmic RNA (7SL RNA). The particle was previously shown to function in protein translocation across and protein integration into the endoplasmic reticulum membrane. Homogeneous signal recognition particle preparations were visualized by electron microscopy (i) after negative staining, (ii) by dark-field imaging of unstained specimens, and (iii) by platinum-shadowing. The results of each of these different techniques indicate that the signal recognition particle is a rod-shaped particle 5-6 nm wide and 23-24 nm long.

Animals↗
PubMed1978

Radiation exposure and recognition of electron microscopic images of protamine at high resolution.

The effect of radiation exposure on visual recognition of individual macromolecules of the protein protamine was examined using high resolution electron microscopy in scanning transmission, fixed beam transmission, dark field and bright field, and recording of images on plates or via video imaging systems including image intensifiers and digital image storage. Loss of recognition of protamine, including its 5 A substructure, followed approximately three-hit kinetics with a Do on the exponential portion of the curve of about 470 e/A2. In spite of the inevitable chemical damage at high doses, virtually all molecules in orientations that exhibited the characteristic protamine structure could still be recognized in dark field scanning transmission or fixed beam bright field at 100-200 e/A2. Recognition fell from 30 to 6% when doses were increased from 1000 to 2000 e/A2 in fixed beam dark field. Exposure rates, varied over seven orders of magnitude from 0.15 e/A2-s to 3 X 10(6) e/A2-s, had no effect at all on the recognition of structures.

Animals↗
PubMed1978

Structure analysis of small proteins by electron microscopy: valinomycin, bacitracin and low molecular weight cell growth stimulators.

Dark field electron microscopy was combined with optical filtering to study at high resolution the structure of the cyclopeptide antibiotics, bacitracin and valinomycin, and two proteins of unknown structure, LMW-CSA N and B, low molecular weight granulocyte colony stimulating activity isolated from medium conditioned with normal or leukemic leukocytes. For bacitracin and valinomycin the images faithfully represented the known structural features at a resolution of 0.5 nm or better, depicting a two-ring structure for bacitracin, as well as the position of the potassium ion in valinomycin. Both proteins of unknown structrue had at least one cyclic peptide portion. LMW-CSA N had a size of 2.0 nm, LMW-CSA B of 2.4 nm. A potential site of the calcium ionophoric activity in the latter protein was found to be in the larger of the two ring portions constituting the molecule.

Bacitracin↗
PubMed1977

Platinum - dimethylsulphoxide as a specific nucleic acid reagent for base sequence determination by electron microscopy.

The reaction of platinum (II) - dimethylsulphoxide complex with the bases of the nucleic acids were investigated with a new towards their use as heavy atom markers for base sequence determination by electron microscopy. Both at pH 6.0 and pH 7.5 one platinum atom was bound simultaneously to the pyrimidines and two to adenine, while at the lower pH one platinum, and at the higher pH, two platinum atoms were bound to guanine. The stain therefore appears to be useful to determine the guanine and adenine sequence in single strands of RNA and DNA. Where complementary strands are available the complete sequence determination of all four bases should be possible.

Base Sequence↗
PubMed1977

Signal to noise enhancement in dark field electron micrographs of vasopressin: filtering of arrays of images in reciprocal space.

A technique for filtering arrays of images of dispersed molecules is presented which takes advantage of the crystallographic properties of regular arrays and the rapidity of optical treatment. A filter in reciprocal space consisting of perforations in a square or rectangular lattice, as determined by the image arrrangement, reduces noise and averages the images simultaneously by transmitting only regularly recurring image structure. The filter is universal for all image contents and introduces no additional biases. The signal to noise improvement approaches square root N for N independent images of the same molecule in the same configuration. The procedure which is simple, rapid and inexpensive, is demonstrated with the aid of dark field electron micrographs of the protein vasopressin and combined with iodination of that molecule to elucidate its structure.

Crystallography↗
PubMed1977

Iodinated E. coli 70S ribosomes as a radiocolloid of uniform particle size for lymph-node and liver scanning.

As an example of the use of biologic particles as carriers for radioactive tracers, E. coli 70S ribosomes were labeled with I-125 using chloramine-T. The labeled ribosomes, after treatment with glutaraldehyde, were injected into rabbits either subcutaneously (through the dorsum of the foot) or intravenously (through the ear). After subcutaneous injection, 40% of the activity accumulated in the lymph nodes during the first 5 hr, and the 70S ribosomal particles were shown to remain within the lymphatic system for at least 8 hr. After intravenous injection, 71% of the activity was detected in the liver within minutes by scintigraphic techniques. The effective half-time of the label in the liver from glutaraldehyde-treated I-125-tagged 70S ribosomal colloidal particles is 4-5 hr. No pyrogenic response was observed. Barring any deleterious side effects, the results indicate that biologic cell components of definite dimensions (in this case E. coli 70S ribosomes about 20 nm in diam) could be considered as radiocolloids for lymph-node and liver imaging.

Animals↗
PubMed1975

Three-dimensional structure of herring sperm protamine Y-I with the aid of dark field electron microscopy.

High resolution electron micrographs of herring sperm protamine (clupeine) Y-I provide sufficient detail to constrain the folding of the known amino-acid sequence of the protein into a unique three-dimensional configuration. The structure consists of a loose helix of turns of various sizes held together at one edge, spread apart along the other. This form appears to represent the shape of several fish protamines.

Animals↗