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Biomedical subjects

A Engel

Publications and source records attributed to A Engel.

At least 307 records · Page 17Linked to original sources
PubMed1984

Diagnostic radiology in wartime.

During the Lebanon War, 1982, over 80% of the wounded were sent from the triage area of the hospital directly to the radiology department. This article reports changes in the working pattern and organization of the department that were instituted for emergency treatment in wartime, and describes radiological examination methods for different organs. Computerized tomography is emerging as the most important diagnostic tool in addition to conventional radiological examinations.

Abdominal Injuries↗
PubMed1983

Two-dimensional crystal packing of matrix porin. A channel forming protein in Escherichia coli outer membranes.

Two-dimensional crystalline porin sheets were obtained by reconstitution of monodisperse protein trimers and phospholipids (dimyristoylphosphatidylcholine) by detergent dialysis, analogous to the reconstitution method used for functional tests (Schindler & Rosenbusch, 1981). Three different packing arrangements were observed: two were hexagonal (with p3 symmetry and lattice constants of 9.3 nm and 7.9 nm), and one rectangular (a = 7.9 nm, b = 13.9 nm). The different crystals could be correlated to phospholipid-to-protein weight ratios of 0.16 to 0.72. At the higher ratio, large hexagonal lattices predominated. Higher lipid ratios did not reveal other crystal forms. The packing arrangement of the large hexagonal form appears very similar to the hexagonal habit of three-dimensional crystal forms (Garavito et al., 1983). The shape of the stain-penetrated triplet indentations appeared conserved in the crystal forms to a resolution of 2.2 nm. The mass distribution between triplets, however, were significantly different. They are likely to correspond primarily to lipids. Mass determinations of unstained porin by scanning transmission electron microscopy showed that unit cells consisted of single trimers. The mass found (100,000 daltons) is in good agreement with the value obtained by sedimentation equilibrium analysis.

Bacterial Proteins↗
PubMed1983

Computed tomography in the diagnosis of adrenal pathology.

Computed tomographic diagnosis of adrenal pathology, based on experience with 13 cases, is presented. These include five pheochromocytomas, two functioning cortical adenomas and one case each of nonfunctioning adenoma, adrenal cyst with adenoma, carcinoma, metastasis, and bilateral hyperplasia. One additional case of a small adrenal tumor of undetermined nature was probably a small nonfunctioning adenoma. The smallest tumor detected was 25 mm in diam and the largest was 150 mm. Other imaging modalities employed were mainly conventional urography with tomography and ultrasonography. By these means only the larger adrenal tumors were detected. The relative merits and drawbacks of other imaging procedures are discussed and compared to computed tomography. Computed tomography should be the initial imaging procedure of choice when adrenal pathology is suspected.

Adenoma↗
PubMed1982

Mass mapping of a protein complex with the scanning transmission electron microscope.

A mass map of the hexagonally packed intermediate layer (HPI-layer), a regular protein monolayer from the cell envelope of Micrococcus radiodurans, has been obtained by scanning transmission electron microscopy. Samples were freeze-dried within the microscope, and low-dose images were recorded in the dark-field mode directly in digital form and processed by correlation averaging. The averaged projection of the unstained structure--i.e., the mass map--thus calculated shows a resolution to 3-nm period and reveals morphological features consistent with those obtained by negative staining. The mass of individual morphological domains was extracted by using variously the mass map itself or an average from a negatively stained HPI layer to define the domain boundaries. Protrusions as small as 1,300 daltons could be measured reproducibly within the unit cell of 655,000 daltons. The method developed opens an avenue to identify molecular species in situ and to correlate topographic information with biochemical data.

Bacterial Proteins↗
PubMed1982

Percutaneous transluminal angioplasty of the iliac and lower limb vessels: one year's experience.

Percutaneous transluminal angioplasty (PTA) based on the angiographic technique consists of the use of fluoroscopically monitored special catheters to relieve stenotic segments of recanalize occlusive lesions of the vascular tree. In the course of one year, 192 patients were evaluated angiographically for peripheral vascular disease, of whom 32 were selected for PTA. Twelve patients had PTA for the iliac vessels with a success rate of 83%; 20 patients had PTA for the lower limb arteries with a 60% success rate. The end results depended on the nature of the underlying lesion, with totally occluded arteries having the poorest outcome. The method and the results are described, and the value of the procedure, as reflected in the literature and from our experience, is discussed.

Adult↗
PubMed1980

Purification of acetylcholine receptors, reconstitution into lipid vesicles, and study of agonist-induced cation channel regulation.

We report the purification of acetylcholine receptors with active agonist-regulated cation channels from Torpedo californica electric organ tissue by five methods. In one method, previously used by others, contaminating proteins were removed from partially purified membranes by alkaline extraction, preserving membrane integrity throughout the procedure. In the other four methods, acetylcholine receptors were purified after solubalization with sodium cholate. The continual presence of soybean lipid in mixed micelles with cholate was required to prevent irreversible inactivation of the cation channel. Solubilized receptors were purified by affinity chromatography using either Naga naja siamensis toxin III or concanavalin A coupled to agarose. Sucrose gradient centrifugation was also used to purify solubilized receptors. The best method combined affinity chromatography on toxin-agarose and concanavalin A agarose. Receptors purified by all five methods were incorporated into soybean lipid vesicles by the cholate dialysis technique. The agonist-regulated cation channels of the receptors were equally active after reconstitution, independent of the method used for purification. All reconstituted vesicle preparations were similar in preferential orientation of acetylcholine receptor toward the external surface, dose-response to carbamylcholine, carbamylcholine-induced desensitization, and carbamycholine-induced influx of 22Na+ per mol of receptor. Carbamylcholine-induced 22Na+ influx/receptor was greater after reconstitution than in native vesicles. This was because, in native vesicles, carbamylcholine-induced 22Na+ influx was limited by equilibration of the internal volume of the vesicles with the external 22Na+ concentration, whereas in reconstituted vesicles 22Na+ influx was limited by desensitization of the receptor molecule. We demonstrate that only one of the two toxin binding sites on the receptor monomer, the one which can be affinity alkylated with 4-(N-maleimido)benzyltrimethylammonium, controls the carbamylcholine-induced opening of the cation channel.

Acetylcholine↗
PubMed1980

Self-assembly of single and closely spaced nucleosome core particles.

Self-assembly of DNA with the four core histones but in the absence of H1 generates nucleosome core particles which are spaced randomly over large distances. Closely spaced core particles, however, exhibit a preferred short linkage which is not a multiple of 10 base pairs. They bind about 140 base pairs whereas apparently shorter DNA lengths per nucleosome observed after digestion with micrococcal nuclease are the result of degradation from the ends. The DNA length of one superhelical turn in the core particle is 83 +/- 4 base pairs. Single core particles may bind more DNA than closely spaced core particles but probably less than two full turns of 168 base pairs. The internal structures of single and of native core particles are very similar as judged by their amount of DNA, sedimentation coefficient, appearance in the electron microscope, and digestion with DNase I. In addition to core particles, a particle is described which sediments at 9 S and consists of 108 base pairs of DNA bound to the histone octamer. It appears to be the smallest stable "core particle" but it is not a degradation product of the 146-base-pair core particle. Digestion of end-labeled 9 S and nucleosome core particles with DNase I shows distinct differences.

Animals↗