Biomedical subjects

M Schatz

Publications and source records attributed to M Schatz.

95 records · Page 6Linked to original sources

PubMedDate not supplied

Structure of Lumbricus terrestris hemoglobin at 30 A resolution determined using angular reconstitution.

The three-dimensional (3D) structure of the giant hemoglobin of the common earthworm Lumbricus terrestris was determined from cryomicroscopical images of a vitrified molecular solution. From about 5000 molecular images, the best-fit 3D structure was calculated using recently developed analysis techniques. Multivariate statistical analysis data compression and automatic classification were used to find the characteristic projection images of the oligomer. The angular reconstitution approach was then applied to find the Euler angle orientations of these characteristic views. The Lumbricus hemoglobin molecule has an overall D6 (622) point-group symmetry and is found to have a local threefold symmetry axis within the 1/12th subunit. This additional symmetry appears to predict the presence of 36 abcd globin tetramers in the Lumbricus hemoglobin or a total of 144 heme chains for the whole oligomer. A distinct doughnut-shaped structure is elucidated in the center of the molecule. This central subunit, representing around 10% of the protein volume, may consist of non-heme-containing linker chains found generally in giant annelid hemoglobins.

Animals↗

PubMedDate not supplied

A new generation of the IMAGIC image processing system.

One of the aims of modern microscopy is to quantify two-, three-, or even four-dimensional phenomena in biology, medicine, and material sciences. The requirements imposed on software by such data processing are exemplified by the design considerations of the IMAGIC-5 software system. This system includes facilities for multivariate statistical analysis of large data sets, for correlation averaging of two-dimensional crystals, and for three-dimensional reconstruction of macromolecular structures. The molecules may be arranged as two-dimensional crystals, as helices, or as single particles with arbitrary pointgroup symmetry. IMAGIC's novel angular reconstitution approach allows for the rapid determination of three-dimensional structures of uncrystallized molecules to high resolution. The general organization, user interaction strategy, file structure, and extendibility of IMAGIC are discussed and illustrated with some practical examples.

Animals↗

PubMedDate not supplied

Invariant classification of molecular views in electron micrographs.

Biological macromolecules can exhibit many different orientations in electron microscopical preparations. In particular in vitreous-ice-embedded specimens, the number of different views can be high. Existing techniques of analysis require the alignment of the molecular views relative to one or more reference images with cross-correlation ("matched filtering") techniques and are somewhat unsatisfactory because of the high noise level and the large number of different views in such images. We here propose a method in which first rotation-, translation- and mirror-invariant functions are derived from the large set of input images. These functions are subsequently classified automatically using multivariate statistical classification techniques. The different molecular views in the images can therewith be found without bias, provided that a statistically significant number of copies of the views are present in the data set. The basic ideas are exemplified with realistic model data.

Fourier Analysis↗

PubMedDate not supplied

Diagnosis and management of rhinitis during pregnancy.

Chronic nasal symptoms occur commonly in pregnant women. The most frequent causes of rhinitis during pregnancy are allergic rhinitis, bacterial rhinosinusitis and rhinitis medicamentosa. The appropriate diagnosis in the individual pregnant woman can usually be established on the basis of the history, physical examination and nasal cytology. Benefit-risk considerations in the management of gestational rhinitis are discussed in detail.

Diagnosis, Differential↗

PubMedDate not supplied

Osteoporosis in corticosteroid-treated asthmatic patients: clinical correlates.

This study sought to identify clinical and laboratory characteristics associated with the development of osteoporosis in 44 corticosteroid (CS)-treated asthmatic patients. Percentage predicted bone density was inversely correlated with both the duration of CS therapy (r = -.39, p = 0.009) and 24-hour urine calcium excretion (chi 2 = 5.2, p = 0.022). Bone density was not related to prednisone equivalent dose, alternate day versus daily therapy or serum cortisol levels. These data suggest that (1) long duration of CS therapy and increased urine calcium may identify patients at increased risk of developing CS-induced osteoporosis, and (2) urinary loss of calcium may be of particular importance in the pathogenesis of this condition.

Adrenal Cortex Hormones↗