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Biomedical subjects

G Fischer

Publications and source records attributed to G Fischer.

At least 487 records · Page 27Linked to original sources
PubMed1985

[Demonstration of biological processes in model space or: in search of new natural constants].

It is possible to comprehend the mathematical and geometrical pattern of functions and parameter-descriptions as transformation function. In this manner, the Einstein's equation between mass and energy will be better conceivable, in which also information can incorporated as a view of matter. From geometrical aspect, a so called "material unit sphere" is originated which can be used as a model for description of biological processes. So the material unit sphere takes the same position in biology as the complex numerical plane established by Gauss used in electrical engineering. In this sphere, a force vector is calculable as the reason for processes of growth. For the developed method, new natural constants will be necessary which have to be find by measurements.

Animals↗
PubMed1985

[Neurinoma of the posterior cerebral fossa and mitral valve prolapse. Possible association and study of possible peri-operative consequences on rhythm].

27 patients with an acoustic neurinoma were submitted to a complete cardiological survey oriented towards the detection of mitral valve prolapse (2D echo) and ECG signs of a particular risk of arrhythmia (standard ECG and continuous Holter monitoring). 9 of these 27 patients presented MVP, but none of them presented any serious ventricular arrhythmias. The corrected QT interval was significantly longer in patients without MVP. The frequency of the association of MVP and acoustic neurinoma can not be explained simply by the female predominance of the series and its should be interpreted with reservation in the absence of a control series. The absence of pre-operative arrhythmia does not exclude the potentiating role of MVP in the development of certain cases of unexplained post-operative death.

Adult↗
PubMed1985

[Early surgery of ruptured aneurysms. A factor in preventing ischemia].

110 patients with ruptured aneurysms were operated on within 4 to 96 hours after subarachnoid hemorrhage. Clinical grades (Hunt) were: 1-2-3 in 93 cases and 4-5 in 17 cases. Among the patients grades 1-2-3, 81% had a good out come without any neurological abnormality, among the patients graded 4-5, only 27% had a fair out come. Cerebral ischemia has been noted (CTS can + neurological deficits) in 7 cases only among patients graded 1-2-3 (93 cases). The results, concerning ischemia, are better than the natural course of ruptured aneurysms and better than the course in series with delayed operation. Probably vasospasm is not alone to create ischemia.

Adult↗
PubMed1984

Conformational specificity of chymotrypsin toward proline-containing substrates.

A number of peptide-4-nitroanilide substrates containing proline within the peptide chain have been synthesized and subjected to chymotryptic hydrolysis. Values of kcat and Km have been obtained from measurements at pH 7.8 and 25.0 degrees C. Kinetic studies at high enzyme concentrations up to 6.0 X 10(-4) mol X 1(-1) have allowed the evaluation of the conformational specificity of chymotrypsin due to the observation of various kinetic phases during the time-course of the reaction. When proline occupies the P2 position within the peptide chain, it is shown that the enzyme cleaves only the trans isomer of the substrate. The conformational specificity has also been studied for proline in P4 and P5 positions of the substrate. In some cases, an enzyme-catalyzed hydrolysis of the cis isomer was detected. From the amplitude ratios and the rate constants of the kinetic phases, information about the structural dependency of the cis/trans interconversion could be obtained. Charged residues N-terminal to the isomeric bond are of little influence on either cis/trans ratio or the rate of cis to trans interconversion. Extending the peptide chain N-terminal to the isomeric bond by alanine decreases to a low extent the cis content and increases the rate constant of the trans isomer formation.

Aniline Compounds↗
PubMed1984

Growth requirements of immature astrocytes in serum-free hormonally defined media.

A chemically defined serum-free medium is described that has been optimized for the selective growth of immature astrocytes starting from early postnatal mouse cerebellar cultures. The medium is a modification of one described recently [Fischer et al, 1982] and consists of epidermal growth factor (EGF, 10 nM), transferrin (10 micrograms/ml), insulin (10 micrograms/ml), and bovine serum albumin (BSA, 1 mg/ml) in BME with Earle's salts. None of these constituents of the medium alone nor combinations of two of them can stimulate the proliferation and survival of immature astrocytes. Only with a combination of EGF and transferrin together with either insulin or BSA can proliferation of the cells be obtained. For optimal growth all four constituents are needed. However, the immature astrocytes can only grow for a limited time period of about 2-3 wk in this medium. Therefore they can be selected for and characterized but not continuously cultivated in this medium.

Animals↗
PubMed1984

Intralobular distribution of UDP-glucuronosyltransferase in livers from untreated, 3-methylcholanthrene- and phenobarbital-treated rats.

A 3-methylcholanthrene-inducible enzyme form of UDP-glucuronosyltransferase has been localized within the liver lobule both immunohistochemically and enzymatically in microdissected centrilobular and periportal liver tissue. Livers of untreated, 3-methylcholanthrene- and phenobarbital-treated rats have been compared. The enzyme was detected in hepatocytes throughout the liver. However both immunohistochemical determination of the enzyme level and biochemical determination of its activity towards 1-naphthol revealed a heterogeneous distribution of the enzyme. In untreated controls and 3-methylcholanthrene-treated rats both enzyme activity and histochemical staining was highest in centrilobular hepatocytes. However, after phenobarbital-treatment enzyme staining and activity was highest in periportal hepatocytes, suggesting that the differentially inducible enzyme activities may be localized in different zones of the liver lobule. The results demonstrate that the 3-methylcholanthrene-inducible UDP-glucuronosyltransferase is preferentially expressed in centrilobular hepatocytes.

Animals↗
PubMed1984

Molecular analysis of hexahydro-1H-indeno[1,2-b]pyridines: potential antidepressants.

Biological tests indicate hexahydro-1H-indeno[1,2-b]pyridines to be potential human antidepressants with additional stimulating properties. Two diastereomeric series with H4a,H5-trans,H4a,H9b-cis and H4a,H5-cis,H4a,H9b-cis configurations have been tested biologically. The results revealed that the H4a,H5-cis,H4a,H9b-cis series and the ortho-substituted 5-phenyl H4a,H5-trans,H4a,H9b-cis compounds lack activity. Neither the conformation with lowest potential energy nor any other electron-derived parameter correlate with these data. The only relevant difference between the active and the inactive compounds detected thus far is the rotational barrier of the phenyl in the 5-position. The conclusion was reached that certain conformations, which do not resemble those of lowest potential energy, cannot be adopted by the inactive compounds. Therefore, the interaction of the drug with the binding site, responsible for its biological activity, appears to be governed by a dynamic process. This process is characterized by a transformation of the conformation of lowest potential energy to one with an energy content above the minimum.

Antidepressive Agents↗
PubMed1984

[Determination of dipeptidyl aminopeptidase activities in the cerebrospinal fluid].

The investigation of enzyme activity in cerebrospinal fluid has been without relevant results for laboratories analysing spinal fluid. For neurochemical purposes, it is interesting that the Substance P is convered by Depeptidyl-aminopeptidase IV (DP IV), liberating dipeptides. The hydrolysis of nitroanilids of the form Xaa-Pro-NHNp in cerebrospinal fluid was analysed using them as peptidases substrates. Finally a method for measuring the activity was proposed.

Dipeptides↗
PubMed1984

[Lumbosciatica caused by spondylolisthesis. Results of the surgical treatment by facetolaminectomy and interbody arthrodesis by the posterior approach in a series of 66 cases].

66 patients with spondylolisthesis were reviewed after surgical procedure with a follow-up period of more than a year postoperatively. The indication for the operation was disabling sciatica in all patients. 4 patients had undergone prior excision of the herniated disc. All the patients underwent a removal of the loose posterior element as suggested by the Gill procedure and intervertebral body fusion using a posterior surgical approach. The surgical procedures with only one regressive neurological complication are described. The results are considered from a clinical and anatomo-radiological point of view. In this series 86.5 percent of 66 patients became sciatica-free. 62 percent of the total series rated the end result as excellent or good. 92.4 percent of the patients demonstrated bony fusion between the two grafted vertebrae. The benefits of posterior laminectomy with interbody fusion are also attractive for spondylolisthesis with sciatica.

Adolescent↗
PubMed1984

[Epidermoid cysts of the cerebellopontile angle. 6 cases].

6 cases of cerebello-pontine angle (CPA) epidermoid cysts were encountered from 1970 up to 1983. This series accounts for 3,3% of 177 CPA tumours operated on during the same period. Epidermoid cysts result from heterotopia of ectoblastic tissue and CPA is their most frequent site of development. The wall of the cyst is composed of a stratified squamous epithelium. The inside of the cyst is filled with soft waxy material resulting from the desquamation of keratin of the cyst wall. Macroscopically, the cyst is extensive and usually closely attached to the brain stem, cranial nerves and vessels. The commonest clinical picture is that of a trigeminal neuralgia usually typical of tic douloureux. Plain x-ray films of the skull disclose no abnormalities. Air encephalography was performed in an early case: it showed an obliteration of the cerebello pontine cistern by the cyst mass, with no air injection of the tumor as mentioned elsewhere. Computerized tomography made other procedures obsolete in our 4 latest cases: it showed a non-enhancing low-density mass filling the CPA. Hypodensity characteristics can make differentiation from dermoïd and arachnoid cysts. In a patient, auditory evoked response were lengthened bilaterally and suggested a brain stem compression rather than a cochlear nerve involvement. Operative treatment was performed in all of our 6 patients through a suboccipital craniotomy with the aid of the operative microscope. The aim of surgery should be, whenever possible, total removal of the capsule. A partial section of the fifth nerve is not needed. No patient died postoperatively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

[Determination of enzymatic catalysis for the cis-trans-isomerization of peptide binding in proline-containing peptides].

The rates of cis to trans interconversion of Glt-(Ala)n-Pro-Phe-4-nitroanilides (n = 1-3) were estimated by means of a two-step process with chymotrypsin as the trans-substrate cleaving activity. By the aid of this system, pig kidney and several other tissues contained demonstrable catalytic activity against the cis to trans interconversion of the proline containing peptides. The active protein fraction was purified 38-fold from pig kidney cortex by ammonium sulfate precipitation and a series of column chromatographic techniques. Activity was detected against the cis to trans interconversion of Glt-Ala-Ala-Pro-Phe-4-nitroanilide to a different extent. No activity was found with Phe-Pro-4-nitroanilide. With respect to the substrate specificity, this enzyme must be classified as a peptidyl-prolyl cis-trans-isomerase. The enzyme was strongly inactivated by p-chloromercuribenzoate, sodium dodecylsulfate, Hg2+- and Cu2+-ions, but was not inhibited by metal chelators, diisopropylphosphorofluoridate and chlorotosylamidophenylbutane. The activity is abolished by incubation with trypsin. The enzyme is heat sensitive at 50 degrees C. The results presented in this paper suggest a new type of enzymes, characterized by catalytic activity against conformational interconversions. The possibility of the location of the enzyme on ribosomal particles is discussed.

Amino Acid Isomerases↗
PubMed1984

Prolonged cholestatic jaundice and leukopenia associated with piroxicam.

A case of prolonged cholestatic jaundice and leukopenia occurring in a 60 year old wh piroxicam--a non-steroidal antiinflammatory agent--is reported. Histological examination of liver biopsy revealed pronounced canalicular and intracellular bile retention. After discontinuation of the drug serum bilirubin declined to normal values over a period of 10 weeks.

Anti-Inflammatory Agents↗
PubMed1984

[Biodynamics].

The definition of a biological impulse's law is possible by the assumption of a biological axiom on a physical level with the Newton's axiom. Hence it follows a unique definition of velocity of growth and of acceleration of growth. With help of this significant quantities and of derived biological equations, hence it follows a closed biological system of quantities as a system of 4 main quantities which is possible to fasten with a lock to SI-System by power. The main quantity is biological force which appear as a vector with n dimensions. With consideration also of information it's possible to derive a biological unit of space which hold this vector. This space allows to derivate 2 more transformation relations analogous the Einstein's relation.

Biomechanical Phenomena↗