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Biomedical subjects

A Engel

Publications and source records attributed to A Engel.

At least 271 records · Page 15Linked to original sources
PubMed1989

Rapid isolation of OmpF porin-LPS complexes suitable for structure-function studies.

A gentle and rapid isolation procedure is described yielding fractions containing better than 95% pure OmpF porin of Escherichia coli BE with different amounts of bound lipopolysaccharide (LPS). The procedure employs continuous free-flow electrophoresis (FFE) in the presence of detergent above its critical micelle concentration. Total yields of around 45% were typically obtained when porin-enriched membrane extracts were processed. By use of analytical ultracentrifugation a molecular mass of 114,000 and a sedimentation coefficient S20,w of 5.0 S were determined for porin trimers containing approximately 1 mol of tightly bound LPS. This porin readily formed 3D crystals suitable for high-resolution X-ray diffraction analysis. Three other porin-LPS isoforms isolated by FFE revealed molecular masses of 120,000, 124,000, and 151,000, suggesting that, in addition to the tightly bound LPS, 1, 2, and 8 mol of loosely bound LPS were present per mole of porin trimer. Each of the four different isoforms was suitable for reconstitution into highly ordered protein-lipid membrane arrays. The membrane crystals obtained with the 151-kDa isoform exhibited a unit cell polymorphism similar to that previously reported.

Bacterial Outer Membrane Proteins↗
PubMed1989

Nonocclusive ischaemic bowel disease in patients on chronic haemodialysis.

Six patients with chronic renal failure on longstanding haemodialysis are presented, in whom nonocclusive bowel ischaemia occurred as a rare complication of their underlying disorder. Factors implicated in the development of bowel ischaemia in these patients are chronic constipation resulting in increased intraluminal pressure on the bowel wall, premature and progressive arterial disease and bouts of hypotension accompanying the haemodialysis procedure. Contrast studies of the bowel and computed tomography examination can suggest the diagnosis, but angiography alone provides the exact answer in demonstrating nonocclusive mesenteric ischaemia. In patients with chronic renal failure and longstanding dialysis presenting with abdominal symptoms this diagnosis should be considered.

Aged↗
PubMed1989

Mammographic wire-guided biopsies in non-palpable breast lesions.

The use of mammography, both for diagnostic and screening purposes, is steadily increasing. It is a very sensitive examination method; findings such as an ill-defined or spiculated mass, clustered, irregular and dense microcalcifications, asymmetric densities or architectural distortion, are suggestive of malignancy. These findings are often not specific enough to make an unequivocal diagnosis of malignancy, and they are frequently not palpable. The presence of clinically occult, but mammographically present findings warrants biopsy to determine their histological nature. In order to avoid unnecessarily large biopsies and to assure the removal of the suspicious portion of the breast, precise localization in necessary, guided by mammography. Using a needle-hookwire method, 87 biopsies were done for non-palpable breast lesions detected among 3,196 mammographies performed. Experience with this method and the results show that 17 patients, i.e. every fifth biopsy, had a malignancy. In 5 patients out of 17, the findings proved to be in situ carcinoma. In another group of 17 women the biopsy result was atypical epithelial proliferation, considered to be a transitional phase of in situ carcinoma.

Adult↗
PubMed1989

Determination of protein and nucleic acid concentration and localization of specific elements by scanning transmission electron microscopy.

Elastic and inelastic dark-field micrographs simultaneously recorded by the scanning transmission electron microscope (STEM) provide structural and quantitative chemical information at a spatial resolution of some nanometers. Simultaneous acquisition is essential as it warrants: (i) the geometrical identity of picture elements (pixels) in these micrographs, and (ii) the identity of recording conditions (focus, electron dose) for the elastic and inelastic images. Suitable off-line processing of such multichannel images allows the concentration of protein or nucleic acid within embedding material to be evaluated. In addition, location and number of chemical elements such as phosphorus can be determined. Theoretical sensitivity is a few phosphorus atoms in a volume of approximately 1000 nm3 (not demonstrated in this paper). Quantitative electron microscopy of this kind, however, requires the influence of mass loss as well as plural scattering to be correctly accounted for. Experimental conditions that provide a sound basis for concentration determination as well as element mapping are discussed.

Animals↗
PubMed1988

Native mitochondrial creatine kinase forms octameric structures. II. Characterization of dimers and octamers by ultracentrifugation, direct mass measurements by scanning transmission electron microscopy, and image analysis of single mitochondrial creatine kinase octamers.

Electron micrographs of negatively stained and metal-shadowed mitochondrial creatine kinase (Mi-CK) molecules purified as described by Schlegel et al. (Schlegel, J., Zurbriggen, B., Wegmann, E., Wyss, M., Eppenberger, H. M., and Wallimann, T. (1988) J. Biol Chem. 263, 16942-16953) revealed a homogeneous population (greater than or equal to 95%) of distinctly sized square-shaped, octameric particles with a side length of 10 nm that frequently exhibited a pronounced 4-fold axis of symmetry. The cube-like molecules consist of four dimers that are arranged around a stain-accumulating central cavity of 2.5-3 nm in diameter. This interpretation is supported by single particle averaging including correlation analysis by computer. Upon prolonged storage or high dilution, the cube-like octamers tended to dissociate into "banana-shaped" dimers. Sedimentation velocity and sedimentation equilibrium experiments yielded an s value of 12.8-13.5 S and an Mr of 328,000 +/- 25,000 for the octameric cubes. An s value of 5.0 S and a Mr of 83,000 +/- 8,000 was found under conditions which revealed banana-shaped dimers. These dimers proved to be very stable, as their dissociation into monomers of 45 kDa (s value = 2.0 S) required 6 M guanidine HCl. Thus, the oligomeric structures observed in the electron microscope are identified as Mi-CK dimers (banana-shaped structures) and cubical Mi-CK octamers assembled from four Mi-CK dimers. The octameric nature of native Mi-CK and the formation of Mi-CK dimers were confirmed by direct mass measurements of individual molecules by scanning transmission electron microscopy yielding a molecular mass of 340 +/- 55 kDa for the octamer and 89 +/- 27 kDa for the dimer. A structural model of Mi-CK octamers and the possible interaction with ATP/ADP-translocator molecules as well as with the outer mitochondrial membrane is proposed. The implications with respect to the physiological function of Mi-CK as an energy-channeling molecule at the producing side of the phosphoryl creatine shuttle are discussed.

Animals↗
PubMed1988

[Sonography of the Achilles tendon and its bursa].

Pain and disturbed function in the sole of the foot leads to damage of the tendo Achilles and to abnormalities in its vicinity. They are frequent consequences of some sporting activities (jogging). Differentiation between bursitis, fat necrosis, degenerative changes in tendons and their rupture and from abnormalities of the ankle joint is important for treatment. In the symptomatic patients whom we examined, the bursa was involved in 72.9% and lesions of the tendo Achilles were found in 62.1%.

Achilles Tendon↗
PubMed1988

Multifocal bleeding due to anticoagulant therapy.

A 62-year-old patient on anticoagulant therapy presented with hemothorax, pulmonary hemorrhages and a high retroperitoneal hematoma with obstruction-infarction of the right kidney. Following plasma infusion and pleural drainage, the clinical condition stabilized and kidney function improved.

Hematoma↗
PubMed1988

High-resolution real-time ultrasonography. Diagnosis and follow-up of jugular and subclavian vein thrombosis.

Thrombosis of the internal jugular and subclavian veins was demonstrated by high-resolution real-time ultrasonography in eight patients. The sonographic findings were an intraluminal mass of low or mild amplitude echoes, loss of respiratory rhythmicity and venous pulsation, absence of vein response to respiratory maneuvers (Valsalva and sniff test) and incompressibility of the thrombotic jugular vein. Follow-up examinations after anticoagulant and local streptokinase therapy allowed monitoring of the treatment. High-resolution ultrasonography is a useful noninvasive technique for the diagnosis and follow-up of therapy in thrombosis of the jugular and subclavian veins.

Adult↗
PubMed1988

Processing of quantitative scanning transmission electron micrographs.

While digital image processing is widely used for 3-D structure reconstruction from tilt-series recorded in the electron microscopy (EM), a few scanning transmission electron microscopy (STEM) specific procedures have been developed which provide us with useful quantitative information on the structure of biological macromolecules and their assemblies. These include determination of the mass- or elemental distribution within the structure under investigation. Simple procedures evaluate the mass of proteinous particles, the mass-per-length of filaments or the mass-per-area of sheets. Averaging of STEM elastic darkfield (DF) micrographs from regular structures has demonstrated the possibility of obtaining mass maps, which can reveal domains as small as 1,000 daltons. While the elastic DF image defines the (regular) structure at high-resolution, thereby providing a rule for averaging, much weaker signals are simultaneously acquired by detectors positioned at specific energy losses. Since many (approximately 500) identical subunits from a single multichannel micrograph can be averaged, and many such averages can readily be accumulated due to the precise morphological characterization obtained from the elastic DF image, an element map is expected to emerge from thus averaged electron energy loss windows.

Computer Systems↗
PubMed1988

Health effects of sunlight exposure in the United States. Results from the first National Health and Nutrition Examination Survey, 1971-1974.

The dermatologic component of the first National Health and Nutrition Examination Survey (N = 20,637), conducted from 1971 through 1974, documented the deleterious effect of ultraviolet radiation on selected skin and eye conditions. Actinic skin damage was more frequent in white men with high as compared with low sunlight exposure, 36.7% vs 23.3%, respectively. Among white women, the corresponding figures were 34.1% vs 18.6%, respectively. Actinic damage was found more often in individuals with light eye color. Basal cell epitheliomas were found in 11.3% of white men aged 65 to 74 years who had severely actinic-damaged skin as compared with 1.0% of those with undamaged skin. Sunlight exposure was positively associated with localized hypomelanism, localized hypermelanism, seborrheic keratoses, senile lentigines, freckles, acne rosacea, spider nevi, varicose veins, venus star, dry skin, wrinkled skin, pterygia, arcus senilis, and a variety of minor oral lesions of the tongue, palate, and buccal mucosa. These findings suggest that a large number of dermatologic conditions, which may in part result from overexposure to sunlight, may be preventable.

Adolescent↗
PubMed1988

Feeding patterns of urban black infants.

Feeding patterns of 116 urban black infants were studied from 3 weeks to 6 months of age. Dietary data were collected using a diet history and a food frequency checklist completed by trained interviewers at each well child clinic visit at 3 weeks and at 2, 4, and 6 months of age. At 3 weeks, 20% of the infants were solely breast fed, 58% were formula fed, and 22% were partially breast fed. Twenty percent of 3-week-old infants were receiving baby foods. This increased to 48% at 2 months, and to 72% at 4 months. By 6 months of age, 98% of infants received baby foods. Nursing mothers tended to introduce baby foods later than formula-feeding mothers. This is consistent with other studies. Commercially prepared baby foods were used much more commonly than were foods prepared at home. Infant cereal was most often introduced first, followed by strained juices, strained fruits, strained vegetables, combination dinners, desserts, and plain meats, in that order. Table foods contributed very little to caloric intakes of infants less than 4 months of age. Liberal amounts of water and sugar water were given to infants in this cultural group.

Adult↗
PubMed1987

[Importance of the ossicle and therapy of Osgood-Schlatter disease].

If ossicles occur within the disease pattern of Osgood-Schlatter disease (apophysitis tibialis adolescentium) the duration of the complaints is usually extended to twice the normally expected period. Their shape and location influences the clinical course of the disease. Surgical removal of these ossifications is the therapy of choice if the complaints persist for a relatively long time. With regard to conservative treatment it has been shown on the basis of the duration of healing that functional therapy with an expansion of the ischiocrural musculature is preferable to immobilization of the joint. We consider functional treatment to be justified even if there is an increased formation of ossicles on non-immobilization of the joint, since such ossification occurs with only 20-25% of all cases of Osgood-Schlatter disease and the duration of the complaints is markedly less enhanced than with immobilization measures. As far as the sportsman is concerned, this entails only brief loss of training and the possibility to avoid muscular atrophy of the affected leg by means of physiotherapeutic exercise.

Adolescent↗
PubMed1987

Mathematical model of Klebsiella pneumoniae resistance to amikacin and gentamicin.

1. The resistance of Klebsiella pneumoniae to amikacin and gentamicin was studied by a mathematical model to predict the rate of sensitivity decrease. The results accurately matched experimental data, showing that the model is a reliable predicting tool. 2. The observations were carried out over six years and included 2677 cultures that were positive for K. pneumoniae. At the beginning of the observation period, 85.7% of the cultures were sensitive to amikacin and 40.8% were sensitive to gentamicin. Sensitivity to amikacin showed a surprisingly rapid decrease; at the end of the experimental period, amikacin and gentamicin sensitivities were 33.3% and 27.8%, respectively. 3. We conclude that patterns of resistance of other bacteria could be investigated using this method.

Amikacin↗
PubMed1987

CT guided transgluteal fine needle aspiration biopsy.

CT is a suitable method for evaluation of local recurrence of rectal carcinoma after abdomino-perineal resection, as the presence of a soft tissue mass in the presacral area may be due to either residual changes from the previous surgery, or recurring disease. CT guided fine needle aspiration biopsy with a transgluteal approach was a relatively simple and fast procedure for obtaining cytological proof on the nature of the lesion in 7 out of 9 patients.

Biopsy, Needle↗