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Biomedical subjects

A Henschen

Publications and source records attributed to A Henschen.

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

Hysteretic behaviour of citrate synthase. Site-directed limited proteolysis.

Limited proteolysis of citrate synthase by Astacus protease, chymotrypsin, clostripain, subtilisin and trypsin on primary fragmentation all yielded similarly sized large (Mr 35 000-36 000) and small fragments (Mr 13 500-14 000) but endoproteinase Lys-C gave fragments of Mr 40 500 and Mr 6500. The sites of the proteolytic attack were determined by Edman degradation of the fragmented synthase preparations, Chymotrypsin, subtilisin, trypsin and endoproteinase Lys-C hydrolyse the synthase at positions 323-324 (-Leu-Arg-), 321-322 (-Ala-Val-)/322-323 (-Val-Leu-), 313-314 (-Arg-Val-) and 366-367 (-Lys-Ala-), respectively. Chymotrypsin and subtilisin attack the small domain of the synthase at the loop between helices O and P very near to a catalytic residue, His-320, and abolish all synthase activities. Primary fragmentation by endoproteinase Lys-C and trypsin reduces the catalytic activity in the physiological overall reaction. Both fragmented enzyme species catalyse the hydrolysis and C-C bond cleavage reactions of citryl-CoA in a stimulated fashion compared to the steady-state rates of the native enzyme, and without hysteretic behaviour. The proteolytic cleavage occurs at acetyl-CoA binding sites within the small domain at the loops connecting helices O to P (trypsin) and Q to R (endoproteinase Lys-C) and reduces the affinity of acetyl-CoA. All of the altered kinetic properties of the fragmented enzyme species are related to this reduced affinity. The correlation between structure and function indicated above is strengthened by the unaltered affinity of oxaloacetate towards the fragmented synthase species. None of the proteolytic enzymes applied attacks oxaloacetate binding sites as defined by the structural work. Oxaloacetate inhibits the hydrolysis of citryl-CoA by the fragmented synthases (endoproteinase Lys-C, trypsin) competitively. An explanation is proposed. The isolated small and large fragments (endoproteinase Lys-C, trypsin) were enzymically inactive. Enzymic activity was restored on recombination of the fragments under denaturing conditions. Cleavage of the loops between helices O to P and Q to R by sequential fragmentation with endoproteinase Lys-C and trypsin inactivated the synthase completely. This result lends support to the idea that the open and closed crystal forms of the structural work are interconverted during the catalytic cycle.

Amino Acid Sequence↗
PubMed1984

Human low-molecular-mass kininogen. Amino-acid sequence of the light chain; homology with other protein sequences.

The complete amino acid sequence of the human low-molecular-mass kininogen light chain has been determined. The peptide chain contains 38 amino acid residues. In position 18 the half-cystine residue which forms the disulfide bridge to the heavy chain was found. Alignment of the present sequence with other kininogen light chain sequences indicated that the amino-terminal part of it is species-specific and the carboxy-terminal part is function-specific. Statistically significant internal homologies between various parts of the low-molecular-mass kininogen sequence as well as homologies between parts of the sequences of kininogen and ribonucleases were observed.

Amino Acid Sequence↗
PubMed1984

Boar acrosin is a two-chain molecule. Isolation and primary structure of the light chain; homology with the pro-part of other serine proteinases.

Acrosin (EC 3.4.21.10), the major proteinase of mammalian spermatozoa, has been demonstrated to be a two-chain glycoprotein with an Mr-4200 light chain covalently attached to an Mr-37000 heavy chain. Following mercaptolysis of the disulfide bonds, the two chains were separated by high-performance liquid chromatography on a reversed-phase column. Sequence analysis of the isolated light chain (23 amino acid residues) indicated a considerable sequence homology with the bovine chymotrypsinogen activation peptide (6 out of 15 positions with identical amino acids, i.e. 40% identity) and the pro-part of other serine proteinases (17-22% identity), thus suggesting that the acrosin light chain corresponds to the pro-part of the acrosin zymogen. In position 3, the light chain confers a carbohydrate side chain N-glycosidically linked to the acceptor sequence Asn-Xaa-Thr. Evidence is presented that the acrosin light chain is connected via two disulfide bridges to the heavy chain which contains about 320 amino acids including the active-site residues of the proteinase.

Acrosin↗
PubMed1984

The auricular myocardiocytes of the heart constitute an endocrine organ. Characterization of a porcine cardiac peptide hormone, cardiodilatin-126.

A peptide hormone was extracted from the porcine right atrium following a bioassay for differential vasorelaxant effects on smooth muscle strips from aorta and renal and inferior mesenteric arteries. The isolation procedure included several steps of gel-permeation and ion-exchange chromatography, and high performance liquid chromatography. During the isolation procedure, other peptides of smaller molecular weight were also found, which, in relation to cardiodilatin-126 (CDD-126), are shorter at their N-terminal. Among these, CDD-88 has also been isolated and characterized, and has been established as a prominent member of the cardiac hormone family. The N-terminal and C-terminal segments of the 126 amino acid-containing molecule were synthesized and used to raise region-specific antibodies. The natural peptide was then localized within myoendocrine cells of the right atrium where specific atrial granules are located. Renal effects of cardiodilation were studied in conscious dogs and showed strong diuretic and natriuretic activities. According to our functional studies, cardiodilatin-126 and cardiodilatin-88 possess qualities of a significant hormone family regarding the regulation of extracellular fluid volume and blood pressure.

Amino Acid Sequence↗
PubMed1984

Chlorhexidine-induced degeneration of adrenergic nerves.

Possible toxic effects of chlorhexidine (CHX) on the sympathetic adrenergic ground plexus were studied in whole mounts of albino rat irides using Falck-Hillarp fluorescence histochemistry. CHX dissolved in an isotone , buffered sodium-acetate solution or in 70% alcohol was injected into the anterior chamber of eye. CHX caused a marked and dose-dependent degeneration of adrenergic nerves. Two days after the lowest dose, 0,25 micrograms (5 microliters of a 0.05% CHX solution), approximately 30% of the nerves had disappeared. Almost complete degeneration was observed after the same time with higher doses (2.5 micrograms, 5.0 micrograms, and 7.5 micrograms corresponding to 0.5, 1.0, and 1.5% CHX respectively). Two weeks after the lowest dose, the nerves had regenerated almost completely. With the highest dose used, only some 40% of the normal adrenergic nerve plexus had reformed after 51 days. Alcohol as a solvent did not have an additive effect on the neurotoxic action caused by CHX. The results demonstrate yet another aspect of chlorhexidine neurotoxicity, degeneration of peripheral adrenergic nerve terminals. This suggests that neurotoxic actions on thin unmyelinated fiber systems should be looked for also in the central nervous system (CNS).

Animals↗
PubMed1984

Some toxic effects of lead, other metals and antibacterial agents on the nervous system--animal experiment models.

Modern man is chronically exposed to lead levels in the biosphere, several times higher than the natural level that once existed. There is much concern about the possible adverse effects of this population-wide low-level lead exposure, particularly on the developing organism, where the central nervous system may be a primary target for lead. We have developed animal test systems which permit temporal and spatial discrimination of possible effects of lead and other potentially neurotoxic agents in the environment on the developing central nervous system, as well as on different types of peripheral nerves in the adult individual. In one experimental design, defined areas of the fetal rat brain are grafted to the anterior chamber of the eye of adult rat recipients which are exposed to lead (1% PbAc in drinking water). Such grafts will become vascularized from the host iris and continue their development in oculo. Thus the grafted brain tissue and the host brain will share circulation and therefore be exposed to exactly the same amounts of lead simultaneously. Studies of cerebellar grafts revealed that although there was a normal gross cytological development in the presence of lead, there was a severe, permanent impairment of the spontaneous discharge rates of the grafted Purkinje neurons as observed with electrophysiological techniques long after cessation of the lead treatment. The host Purkinje neurons were not affected. A similar, although less dramatic, impairment of cerebellar function could then be demonstrated in intact animals when newborn rats were given lead (8 mg PbAc/kg i.p.) during the first 20 days of life and then studied as adults. In other areas of the fetal central nervous system grafted to the eye, lead caused disturbed growth (substantia nigra, cortex cerebri). A screening technique for potentially harmful effects on autonomic and sensory nerve terminals in adult rats makes use of intraocular injections of agents to be tested. Morphological and histochemical changes of the innervation apparatus of the iris are then studied in iris whole-mount preparations. Lead causes an adrenergic hyperinnervation of the iris. Computer-based image analysis revealed severe degenerative effects by hexachlorophene and chlorhexidine. These studies demonstrate the usefulness of the intraocular grafts and the intraocular injection technique and the need to apply both structural and functional techniques in order to detect possible neurotoxic actions of xenobiotics. The techniques have revealed hitherto unknown toxic actions of lead on cerebellar function.

Adrenergic Fibers↗
PubMed1983

Purification and properties of guinea-pig submandibular-gland kallikrein.

Guinea-pig submandibular kallikrein has been purified from the glands to electrophoretic homogeneity by conventional procedures. The enzyme is active as a kininogenase, releasing kallidin at a rate of 462 micrograms/min per mg of protein from bovine kininogen, and proved potently hypotensive in the guinea pig and in the dog, properties which indicate its tissue kallikrein nature. The specific activity determined on the substrate N-alpha-benzoyl-L-arginine ethyl ester (11.1 mumol/min per mg of protein) is much lower than that measured with N-acetyl-L-phenylalanyl-L-arginine ethyl ester (483 mumol/min per mg of protein). The latter value is of an order of magnitude comparable with the specific activities of other tissue kallikreins determined with this sensitive kallikrein substrate. The enzyme is a glycoprotein consisting of 237 amino acid residues and containing three to four glucosamine molecules. Its amino acid composition is not identical with that reported for guinea-pig coagulating-gland kallikrein, but is remarkably similar to that of the porcine tissue kallikreins. Apparent Mr values are 29000 (sodium dodecyl sulphate/polyacrylamide-gel electrophoresis) or 34000 (gel filtration). The amino acid sequence of the first 31 N-terminal residues was determined and was found to be closely homologous with that of other tissue kallikreins.

Amino Acid Sequence↗
PubMed1983

The right auricle of the heart is an endocrine organ. Cardiodilatin as a peptide hormone candidate.

A new polypeptide hormone candidate regulating vascular smooth muscle function was extracted from porcine atrial tissue. The purification steps were followed by a bioassay. The hormonally active substance has been analyzed and found to be a small polypeptide exhibiting a molecular weight of about 7500 and is named "cardiodilatin" (CDD). Further chemical data on this new hormone will be published elsewhere. A partial amino acid sequence of cardiodilatin is offered and shows that among the well known hormones or neuropeptides, none exhibit a homologue partial sequence.

Amino Acid Sequence↗
PubMed1983

Hexachlorophene-induced degeneration of adrenergic nerves: application of quantitative image analysis to Falck-Hillarp fluorescence histochemistry.

Possible toxic effects of hexachlorophene (HCP) on sympathetic adrenergic nerves were studied using Falck-Hillarp fluorescence histochemistry on whole-mounts of albino rat irides. HCP dissolved in 5 microliters DMSO, or DMSO alone, was injected into the anterior chamber of the eye. HCP caused a dose-dependent degeneration of adrenergic nerves, first observable after 7 micrograms and profound after 21 micrograms. One and 3 days after 35 micrograms of HCP there was an almost total loss of adrenergic nerves. Regeneration from remaining non-terminal axons led to an almost complete reformation of the adrenergic nerve plexus after 18 days. The results demonstrate a new aspect of hexachlorophene neurotoxicity, degeneration of peripheral adrenergic nerve terminals and suggest that neurotoxic actions on thin unmyelinated fiber systems should be looked for also in the central nervous system (CNS).

Animals↗
PubMed1983

Sauvagine induces release of adrenocorticotropin, beta-endorphin and corticosterone in rats.

The effect of sauvagine, a frog skin peptide, on ACTH, beta-endorphin and corticosterone secretion, was studied in rats. A subcutaneous injection of 5 micrograms kg-1 of sauvagine in rats produced a prompt increase in immunoreactive plasma concentration of ACTH and beta-endorphin, which reached a peak value 15-30 min after the peptide injection. The stimulatory action of sauvagine on ACTH and beta-endorphin secretion was dose related. Intensity and duration of corticosterone secretion, produced by sauvagine mediated ACTH release, was dose-dependent, the threshold dose being 0,5 microgram kg-1 s.c. Pretreatment of rats with dexamethasone-21-phosphate, prevented the corticosterone releasing effect of sauvagine. Sauvagine perfusion (2,1 nM/h) of biogel columns containing isolated and dispersed anterior pituitary cells induced a sharp increase of ACTH levels in the eluate. Considering the high corticotropin releasing potency of sauvagine and its chemical similarity to ovine CRF, it is interesting to hypothesize whether this peptide may represent, in lower vertebrates, an ancestral form of the mammalian hypothalamic releasing factor.

Adrenocorticotropic Hormone↗
PubMed1983

Fibrinogen Manchester: identification of an abnormal fibrinopeptide A with a C-terminal arginine leads to histidine substitution.

Purified samples of fibrinogen Manchester, a congenital dysfibrinogenaemia with impaired fibrinopeptide A (FPA) release, were digested with thrombin. Amino acid sequencing of the fibrin showed that FPA had been completely released. High performance liquid chromatographic (HPLC) analysis of the clot supernatant showed the presence of a new peptide eluting ahead of the normal FPA. The amino acid composition and sequence of the new peptide established its identity as a variant of FPA containing histidine in position 16 instead of the usual arginine. The chromatograms from both siblings with the defect demonstrated that they were heterozygous for this clotting defect.

Amino Acid Sequence↗
PubMed1983

Delayed release of an abnormal fibrinopeptide A from fibrinogen Manchester: effect of the A alpha 16 Arg leads to His substitution upon fibrin monomer polymerization and the immunological crossreactivity of the peptide.

Fibrinogen Manchester is an abnormal fibrinogen with an impaired release of fibrinopeptide A (FPA) and a polymerization abnormality. In the accompanying article we have identified the amino acid substitution in fibrinogen Manchester as A alpha 16 Arg leads to His. When fibrinogen Manchester was digested with low thrombin concentrations approximately 40-50% of the total FPA content was release at a rate similar to FPA release from normal fibrinogen. The fibrin so formed exhibited an impaired polymerization of monomers. Digestion of fibrinogen Manchester with high concentrations of thrombin for prolonged times released the remaining FPA which had an abnormal retention time when studied by high performance liquid chromatography (HPLC). This fibrinopeptide has been shown previously to contain the A alpha 16 Arg leads to His substitution. fibrin resulting from this exhaustive digestion had normal polymerization of monomers. The normal and substituted FPAs were isolated by HPLC and compared in a double antibody competitive-binding assay for normal FPA. The immunological cross-reactivity of the abnormal peptide was reduced, so that approximately 5 times more abnormal peptide was required on a molar basis to displace labelled normal FPA. Normal intact fibrinogen was 10-fold less reactive (on a half molar basis) than free normal FPA and the crossreactivity of fibrinogen Manchester was measurably less than that of normal fibrinogen. It is concluded that immunological measurement alone of FPA released from abnormal fibrinogens may not give a complete description of the kinetics of peptide release if the amino acid substitution lies within the FPA sequence. The combination of radioimmunoassay and HPLC, however, provides a powerful analytical approach that should be useful in classifying and characterizing abnormal fibrinogens.

Blood Coagulation Disorders↗
PubMed1983

Solid-phase synthesis of sauvagine-(17-40).

The solid-phase synthesis of the tetracosapeptide corresponding to the C-terminal amino acid sequence of sauvagine is described. After purification by gel filtration, the polypeptide appeared to possess an acceptable degree of homogeneity, as judged by different kinds of electrophoresis and chromatography, and by automated Edman degradation analysis. Preliminary pharmacological results indicate that the fragment-(17-40) is practically devoid of any sauvagine activity on the circulatory system and endocrine glands; a weak effect on gastric emptying delay has been demonstrated (1% of the natural product).

Amino Acid Sequence↗
PubMed1983

Hemocyanins in Spiders, XVIII. Complete amino-acid sequence of subunit e from Eurypelma californicum hemocyanin.

The complete amino-acid sequence of subunit e of the hemocyanin from the tarantula, Eurypelma californicum, was determined by a combination of manual and automated methods. By limited proteolysis with chymotrypsin, two large fragments (e-CHn 29 and e-CHn 42) were obtained. The large peptides were further cleaved with cyanogen bromide, trypsin (with and without prior blocking of lysine residues), chymotrypsin, Staphylococcus aureus proteinase, Astacus fluviatilis proteinase, or 25% formic acid. The complete chain comprises 621 residues. A remarkable feature of the sequence is a hexapeptide -His-His-Trp-His-Trp-His- which is believed to take part in the binding of copper.

Amino Acid Sequence↗
PubMed1983

Novel structure elucidation strategy for genetically abnormal fibrinogens with incomplete fibrinopeptide release as applied to fibrinogen Schwarzach.

A novel and simple strategy was developed for the structure elucidation of those genetically abnormal fibrinogens in which thrombin is unable to release fibrinopeptide A from the abnormal molecules. The method provides evidence for the Arg leads to Cys exchange at the C-terminus of the fibrinopeptide A sequence. The abnormal fibrinogen was mercaptolysed and then S-amino-ethylated. Upon thrombin digestion, the modified fibrinogen released new peptides, as shown by high-performance liquid chromatography. The amino-acid analysis proved that these peptides correspond to the expected fibrinopeptide A variants. It was therefore concluded that the analysed case of dysfibrinogenemia, designated Fibrinogen Schwarzach, contains an A alpha 16 Arg leads to Cys exchange in the heterozygous form.

Amino Acids↗
PubMed1983

On the structure of functional sites in fibrinogen.

Fibrinogen is involved in many biochemically and medically important processes. In order to obtain a deeper insight into the functional mechanisms of these processes it is necessary to analyse them on the molecular level. The complete covalent structure of human fibrinogen is known, and it is therefore now possible to establish structure-function relationships. For several functional sites the structural equivalent has been well identified, e.g. the thrombin and plasmin cleavage sites, and crosslinking site. For some other sites only the corresponding regions of the molecule are known, e.g. polymerization and calcium-binding sites. However, for many significant physiological functions of fibrinogen the structural basis has not yet been established. On the other hand, there are several regions of the molecule which by evolutionary evidence seem to be of functional importance, but for which no specific functions as yet have been assigned.

Amino Acid Sequence↗