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Biomedical subjects

H Fuchs

Publications and source records attributed to H Fuchs.

At least 109 records · Page 6Linked to original sources
PubMed1984

Modeling Balbiani Ring gene transcription with electron microscope tomography.

Cross-sectional views of mature regions of Balbiani Ring (BR) transcription loops were reconstructed by electron microscope tomography. Balsa wood models were built based upon the resulting tomograms. Coordinates of the centers of the ribonucleoprotein BR granules were estimated and employed to calculate the approximate orientation of the BR transcription unit axis in the plastic section. The density of BR granules per micron of transcription unit axis was estimated. Employing structural parameters for mature regions of BR transcription loops derived from present and previous studies, theoretical calculations were performed to examine potential steric restrictions around the central chromatin axis. Tomograms were also observed and photographed on a varifocal (vibrating) mirror to illustrate the utility of a rapid user-interactive 3-D display.

Animals↗
PubMed1982

Dissociation of C1 and concentration dependence of its activation kinetics.

The activation of the zymogen C1s to the enzyme C1s in the human C1 complex [C1q(c1rC1s)2] was studied as a function of the concentrations of (C1rC1s)2 and C1q which were saturated with oligomers of rabbit IgG. A large concentration dependence of the sigmoidal kinetics was observed in the 2-180 nM concentration range. This was explained by association-dissociation equilibria between the antibody-saturated C1q and various forms of the (C1rC1s)2 complex (unactivated to activated). The establishment of these equilibria (binding constant 2 x 10(7) M-1) was assumed to be fast as compared to the rates of the activation steps (rate constants 10(-3) and 10(-2) sec-1 at 30 degrees C). The fast re-equilibration of the C1 complex explains the finding that small amounts of antibody-saturated C1q catalysed the activation of large amounts of C1s. The interpretation of the kinetic results was supported by a direct demonstration of the dissociation of C1 into C1q and (C1rC1s)2 by analytical and density gradient centrifugation. No difference was found between the rates of activation and the dissociation properties of reconstituted C1 and C1 isolated from serum.

Centrifugation, Density Gradient↗
PubMed1981

Foqus: a FORTRAN program for the quantitative analysis of x-ray spectra from thin biological specimens.

An online FORTRAN program for the quantitative analysis of energy dispersive X-ray spectra from thin biological specimens is presented. The methods of background suppression by digital filtering and peak deconvolution by linear least-squares fitting with measured peak profiles are used. The continuum quantitation method for spectra from thin biological sections as proposed by Hall is applied. The performance of the computer program, utilizing the facilities of a disk operating system, is demonstrated. The routines were optimized for speed, resulting in a run-time of less than 5 seconds on a 16 bit minicomputer for a full quantitation for 7 elements of an energy dispersive thin section X-ray spectrum, including an optional absorption correction. Since no assembly language subroutines are implemented, the restrictions for the use of the program with different computer systems are minimized.

Calibration↗
PubMed1980

Assembly of subcomponents C1r and C1s of first component of complement: electron microscopic and ultracentrifugal studies.

Monomeric C1s (Mr, 85,000; s20,w, 4.3S), a subcomponent of first component of complement (C1), the dimer (Mr, 170,000; s20,w, 6.7 S) of C1r, another subcomponent, and the tetrameric complex (C1r,C1s)2 (Mr, 340,000; s20,w, 8.7 S) are elongated molecules. Hydrodynamic equivalents of cylindrical shape have a diameter of 3.3 nm and lengths of 20 nm for C1s, 36 nm for (C1r)2, and 64 nm for (C1r,C1s)2. In electron micrographs the C1r,C1s complex appears as a chain composed of six to eight globular domains with a contour length of 51 nm. A structure is proposed in which (C1r)2 forms a core to which C1s protomers are associated at both ends. The C1 complex (s20,w, 16.3 S) reconstituted from C1q, C1r, and C1s dissociates under the conditions used for electron microscopy. Some features of the C1 complex are revealed in the dissociation products.

Centrifugation, Density Gradient↗
PubMed1980

The use of frozen-hydrated bulk specimens for x-ray microanalysis.

The recent development of versatile instrumentation has removed a serious obstacle for the use of frozen-hydrated bulk specimens in studies of biological problems. Methods for freezing, fracturing, mounting, etching, and coating are now known and offer a wide spectrum of technical possibilities to choose from for a particular application. However, progress in biological studies is still limited by the problems encountered during the analysis. In order to keep the X-ray source volume commensurate with the size of cells, low accelerating voltages have to be used. Poor peak to background ratios are, thereby, obtained and the sensitivity of the method is deteriorated. Superficial freeze-drying improves the peak to background ratios, but it is no expedient because of the difficulty in determining the degree of dehydration. The most serious problem is specimen charging which occurs even after coating. The degree of charging is not uniform, neither within the sample nor between specimen and standard. Therefore, the determination of relative concentrations becomes uncertain.

Electric Conductivity↗
PubMed1977

[Computed tomography of the pancreas (author's transl)].

The computed tomography gives direct visualisation of the pancreas in a transverse section. Form, size, and changed consistency of the organ can be diagnosed. Being a non-invasive technique it does not stress the patient, and can be applied to the severly ill with acute haemorrhagic pancreatitis. Other indications are chronic pancreatitis, pancreatic abscess, pseudo-cyst and cancer. The differential diagnosis of cancer, especially from chronic pancreatitis, may be difficult. Further methods of investigation such as arteriography or endoscopic retrograde pancreatography may also have to be used.

Abscess↗
PubMed1976

[Rare fistulation in enterocolitis regionalis (Crohn's disease) (author's transl)].

The transmural inflammation in Crohn's disease, the variable localization of the disease and the tendency to a descending spread, all lead to a multitude of possible fistulae, the presence of which is often difficult to demonstrate. This is a report on 5 unusual fistula systems: in 2 cases entero-enteral (one of which with hydronephrosis), 1 case of rectovaginal fistula, 1 case of a branched fistula system in the right buttock, 1 case of fistulae between an abscess system in the spleen "bed" and the greater curvature of the stomach. A radiological and endoscopic diagnosis is important since surgically opened fistula systems heal only with great difficulty or not at all.

Abscess↗
PubMed1976

[Biochemistry of benign-symmetrical lipomatosis (adenolipomatosis Launois-Bensaude, Madelung's disease)].

1. Total lipids, total cholesterol, cholesterol esters, phospholipids, triglycerides and free fatty acids as well as the fatty acids profiles of the different lipid classes were determined in serum, lipomatous and normal adipose tissue. Triglycerides were elevated in patient L's serum. The distribution of serum lipoproteins in this patient's serum showed a type IV according to Fredrickson. All other lipid parameters were within the normal range. Palmitoleic acid was increased nearly in all lipid fractions of the patients' sera as well as in the lipids of lipomatous subcutaneous adipose tissue. 2. The lipomatous adipose tissues of the patients showing no histological abnormalities revealed higher levels of cyclic AMP than normal subcutaneous adipose tissue. 3. Serum uric acid was normal (patient E.), between the normal and pathological range (patient L.) and elevated (patient W.). Urinary uric acid excretion was increased in all three patients. 4. 14C-glycine was overincorporated into urinary uric acid in all three patients. 5. Adenine phosphoribosyltransferase activities in the hemolysates were within the normal range. A decrease of hypoxanthine-guanine phosphoribosyltransferase activities could be demonstrated in two patients' (e., w.) erythrocytes. Erythrocyte phosphoribosylpyrophate synthetase activity was slightly increased in patient L.'s and twice the normal value in patient W.'s erythrocytes.

Adult↗