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Biomedical subjects

K Bauer

Publications and source records attributed to K Bauer.

At least 235 records · Page 13Linked to original sources
PubMed1983

Peripheral hearing loss: implications for clinical dichotic listening tests.

This experiment assessed the extent to which a peripheral hearing loss may confound interpretation of dichotic listening test results in assessment of central auditory deficit. A normal-hearing listener was tested monotically and dichotically with CV nonsense syllables in two conditions. In one, an EAR plug was inserted in the auditory canal to simulate a unilateral conductive hearing loss. In the second, no plus was inserted. Syllables were presented with equal intensity to the two ears for dichotic testing and testing was conducted at several different intensities. With the plug inserted, both magnitude and direction of percent ear advantage varied with test intensity even when monotic speech recognition scores exceeded 95% for both ears. When dichotic tests are used to assess central auditory deficit in patients with peripheral hearing loss, we recommend that the test intensity be at least 10 dB from both the lower and upper knees of monotic performance-intensity functions.

Dichotic Listening Tests↗
PubMed1983

[Interaction of radiographic contrast media with immunoglobulins].

As a special form of contrast medium incidents, various reaction modes between iodinated contrast media and immunoglobulins are described. Theoretical explanations and typical examples are given for each of the four different possible action mechanisms. Diagnostic precautions are proposed in order to avoid unfavourable reactions especially with paraproteins. Special attention is drawn to the antigen-antibody like reaction between iodinated contrast media and IgM paraproteins. Some immunological criteria are recalled to attention, this type of reaction has to meet stringently. Only by this, misinterpretation of inevident conclusions from analogy can be prevented in future similar cases.

Antigen-Antibody Reactions↗
PubMed1982

Biosynthesis of carnosine and related peptides by glial cells in primary culture.

Synthesis of carnosine (beta-alanylhistidine) and related peptides by glial cells in primary culture could be demonstrated. After incubation with [3H]beta-alanine, the radiolabeled dipeptides could be isolated from the cell extract and the culture medium. With gamma-amino[3H]butyric acid, however, rapid degradation of the tracer without significant synthesis of homocarnosine (gamma-aminobutyrylhistidine) was observed. Aminooxyacetic acid, a known inhibitor of gamma-aminobutyryl:alpha-ketoglutarate aminotransferase, inhibits the degradation of gamma-amino[3H]butyric acid very strongly and of [3H]beta-alanine partially. After preincubation of the cells with this inhibitor, incorporation of gamma-amino[3H]butyric acid into homocarnosine and related peptides could be demonstrated.

Alanine↗
PubMed1982

Substrate specificity of an adenohypophyseal endopeptidase capable of hydrolyzing luteinizing hormone-releasing hormone: preferential cleavage of peptide bones involving the carboxyl terminus of hydrophobic and basic amino acids.

The substrate specificity of a peptidase from anterior pituitaries that is capable of hydrolyzing luteinizing hormone-releasing hormone (LH-RH; less than Glu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH2) at the Tyr5-Gly6 peptide bond has been investigated by using inhibitors and model substrates. While trypsin and chymotrypsin inhibitors from plants and animals are without any effect, many microbial protease inhibitors and synthetic peptides containing hydrophobic and basic amino acids inhibit the degradation of radiolabeled LH-RH by this enzyme. The model substrates N-acetyl-Phe-Gly-Leu-beta-naphthylamide, N-acetyl-Leu-Gly-Leu-beta-naphthylamide, and N alpha-benzoyl-Arg-Gly-Leu-beta-naphthylamide are hydrolyzed at the X-Gly peptide bonds; N-acetyl-Gly-Gly-Leu-beta-naphthylamide is not degraded. Hydrolysis of typical amino- and carboxypeptidase substrates was not observed. Degradation of the general protease substrates insulin B chain and denatured hemoglobin also could not be detected. Thus, the enzyme is not LH-RH specific but may be characterized as an endopeptidase that hydrolyzes peptides preferentially at the carboxyl terminus of hydrophobic and basic amino acids.

Amino Acid Sequence↗
PubMed1981

Ontogenesis of neuropeptide degrading enzymes in the mouse brain.

The ontogenesis of neuropeptide degrading enzymes was studied in the mouse brain, from the 10th gestational day up to adulthood. Two activities were followed: the pyroglutamate aminopeptidase and the post-proline cleaving enzyme, using either TRH or specific fluorgenic peptides as substrates. In the hypothalamus as well as in cerebral hemispheres, the specific activities of both enzymes was highest on the 13th fetal day and decline thereafter until the 20-22nd post-natal day, with a plateau around birth. In contrast, a classical peptidase, the leucyl-arylamidase increased only in fetal life, and reached the adult level before birth.

Aging↗
PubMed1981

Specificity of a serum peptidase hydrolyzing thyroliberin at pyroglutamyl-histidine bone.

The substrate specificity of a serum enzyme which degrades thyroliberin (less than Glu-His-Pro-NH2) into pyroglutamic acid and His-Pro-NH2 has been investigated and compared with that of the pyroglutamyl aminopeptidase from calf liver. The latter enzyme has a broad specificity, causing rapid degradation of thyroliberin, pyroglutamyl beta-naphthylamide and luliberin. In contrast, the serum enzyme causes rapid stereospecific cleavage only of the pyroglutamyl-histidine bond of thyroliberin and closely related peptides. Compounds such as less than Glu-Ala, less than Glu-His and pyroglutamyl beta-naphthylamide, which are known substrates of the pyroglutamyl aminopeptidases (such as the liver enzyme), are not substrates of the serum enzyme, and inhibit it only poorly. Pyroglutamyl-containing peptides such as luliberin and neurotensin and thyroliberin analogues such as LLD-thyroliberin, less than Glu-His-Pro-NHCH3, less than Glu-His-Pro-Gly-NH2 and less than Glu-Phe-Pro-NH2 inhibit effectively the degradation of thyroliberin by the serum enzyme, but are not hydrolyzed by this enzyme. The high specificity of the serum enzyme implies a physiological function.

Aminopeptidases↗
PubMed1981

Evidence of age-dependent activity increase of poly(C)-avid-serum ribonuclease in man.

The activity of ribonuclease (E 3.1.4.22) was estimated in sera of 401 normal subjects (normal renal function, no signs of catabolism), age ranging from 16 to 100 years (mean: 50.25 +/- 19.98) with Poly (C) as substrate. Further activity was measured with the substrates Poly (U), Poly (A) and Poly (G) in 10 sera from each age decade between 21-30 years and 81-90 years. Greatest activity was found with Poly (C) as substrate (mean: 15.88 kU/l +/- 9.57). Covariant analysis (age as covariant) revealed no sex-related activity distribution at any age, whereas the age-dependent activity increase was highly significant (p less than 0.001; 11-20 years: 9.48 kU/l +/- 3.07; 81-90 years: 34.72 kU/l +/- 5.88). Activity with the other substrates was very low and constant throughout all ages. It seems to be mandatory to consider the age of the patient when interpreting ribonuclease activity.

Adolescent↗
PubMed1981

Determination of free haemoglobin in serum by an automated assay using 4-aminophenazone and the Cobas Bio System.

A colorimetric method for the determination of free haemoglobin in human serum is described, using 4-aminophenazone as chromogen, and commercially available haemiglobin cyanide solutions as standards. The reaction system is suitable for manual measurements as well as determinations with a centrifugal analyser (Cobas Bio System). Accuracy, linearity and stability of the procedure is shown. A reference interval in sera of normal adults was established, with an upper limit of 5 mg/dl. The alternative use of heparin plasma instead of serum is discussed.

Aminopyrine↗
PubMed1980

Characterization of a nonchymotrypsin-like endopeptidase from anterior pituitary that hydrolyzes luteining hormone-releasing hormone at the tyrosyl-glycine and histidyl-tryptophan bonds.

A neutral endopeptidase which degrades luteinizing hormone-releasing hormone (LH-RH, <GLu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-GLy-NH2) has been purified 900-fold from extracts of bovine anterior pituitary. This Ca2+-independent enzyme of 83 000 molecular weight (as estimated by gel filtration) cleaves LH-RH (KM = 180 microM) at the Tyr5-Gly6-His2-Trp3 bonds. Its activity is inhibited by the SH-reactive agents N-ethylmaleimide and p-(chloromercuri)benzoate but not by the OH-reactive agent diisopropyl fluorophosphate. Hydrolysis of the fluorogenic chymotrypsin substrate glutarkyl-Gly-Gly-Phe-beta-naphthylamide by this endopeptidase could not be detected. These properties differentiate the endopeptidase from chymotrypsin and from a glutaryl-Gly-Gly-Phe-beta-naphthylamide hydrolyzing activity of high molecular weight, which has been isolated from the same tissue and also hydrolyzes internal bonds of LH-RH.

Animals↗