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Biomedical subjects

A Haeberli

Publications and source records attributed to A Haeberli.

At least 73 records · Page 4Linked to original sources
PubMed1985

Iodine content and density of thyroglobulin investigated by isopycnic centrifugation.

The density of in vitro iodinated thyroglobulin (Tgb) molecules, measured by isopycnic centrifugation, increases linearly with their iodine content. In contrast, the iodine to density (I:D) regression for differently iodinated native rat Tgbs is not constant but varies, depending on experimental conditions: For LID-fed rats the slope of the individual I:D regression line of each Tgb decreases linearly with the decreasing mean degree of iodination of the sample (r = 0.9104, P less than 0.01). On the other hand, in Tgb samples synthesized by propylthiouracil-blocked glands, the I:D regression is no longer linear. Rather, a bimodal pattern is obtained revealing a preexisting highly iodinated Tgb pool together with newly synthesized, non-iodinated protein. The results indicate: (a) the mean degree of iodination of a native Tgb cannot be estimated accurately if only its mean density is known, and (b) the degree of heterogeneity of iodination is identical for any in vivo produced Tgb sample with the same iodine content.

Animals↗
PubMed1985

Fibrin formation and platelet aggregation in patients with severe coronary artery disease: relationship with the degree of myocardial ischemia.

Fibrinopeptide A (FpA) concentrations in plasma and in 24 hr urine specimens as well as beta-thromboglobulin (BTG) in plasma were measured in 17 patients with severe angina pectoris, including both stable and unstable angina, and in 19 patients with acute myocardial infarction. Patients with unstable angina had plasma FpA and BTG levels of 5.2 +/- 1.7 ng/ml and 91 +/- 23 ng/ml, respectively. The corresponding concentrations of FpA in the 24 hr urine specimens were 8.2 +/- 1.4 micrograms/24 hr. These values were similar to those measured in patients with acute myocardial infarction and higher than the corresponding levels in patients with stable angina (p less than .05) and in normal control subjects (p less than .01). The similarity of the platelet and coagulation findings in patients with unstable angina and in those with myocardial infarction favors the hypothesis that coronary thrombosis may play a major role in the pathogenesis of acute myocardial infarction.

Angina Pectoris↗
PubMed1984

Effect of heparin on plasma fibrinopeptide A in patients with acute myocardial infarction.

The plasma level of fibrinopeptide A (fpA) was used as an index of thrombin action on fibrinogen in order to investigate the rates of fibrin formation and the effect of heparin on thrombin in patients with acute myocardial infarction. The fpA levels measured on admission in 19 patients with acute myocardial infarction ranged from 1.7 to 12.4 ng/ml and were elevated (greater than 2.5 ng/ml) in 16 patients. A loading dose of 5000 IU of heparin resulted in a significant decrease within 20 min of the mean fpA level (from 5.1 to 2.2 ng/ml; p less than .001) and in an fpA normalization in five of 16 patients. During the following continuous infusion of 20,000 IU of heparin per day, the mean fpA levels measured on day 0, 1, and 2 were 3.0, 3.2, and 3.4 ng/ml, respectively, with 16 of 46 fpA values within the normal range. In 10 additional patients, the effect of higher concentrations of heparin and the consequences of stopping heparin infusion were studied. An additional 5000 IU of heparin injected intravenously during continuous infusion of 20,000 IU of heparin per day resulted in a substantial decrease of the plasma fpA level in three of 10 measurements. The stopping of heparin infusion led to an impressive increase of the mean fpA level (from 3.1 to 12.9 ng/ml; p less than .001) within 2 hr. These data demonstrate increased fibrin formation in patients with acute myocardial infarction and neutralization of thrombin in vivo by heparin.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1984

Blood coagulation and acute iron toxicity. Reversible iron-induced inactivation of serine proteases in vitro.

Coagulopathy is a hallmark of severe ferrous sulfate poisoning in humans and laboratory animals. Although nontransferrin-bound Fe3+ is thought to initiate the disorder, little is known about how it interferes with blood coagulation. At iron concentrations comparable to those of previous animal investigations, we reproduced the coagulopathy, in other words, the dose-related prolongation of the prothrombin, thrombin, and partial thromboplastin time, in human plasma in vitro. Studies of the mechanism by which iron prevents a normal plasma coagulation revealed that the proenzymes of the coagulation cascade and fibrinogen were not damaged by iron. Fibrinogen coagulability and fibrin monomer aggregation were unaffected by very high iron concentrations. Instead, thrombin was markedly inhibited by iron in its clotting effect on fibrinogen and, specifically, in its fibrinopeptide A-generating capacity, the inhibitory effect being reversible upon iron removal by EDTA chelation and gel filtration. Thrombin generation in the presence of iron was reduced as well, indicating an inhibition of one or several other enzymes of the intrinsic coagulation cascade. Because the amidolytic activity of human thrombin as well as factor Xa, kallikrein, and bovine trypsin was also reversibly suppressed by ferrous sulfate as well as ferric citrate, we consider it likely that the coagulopathy occurring in iron poisoning is the consequence of a general, physiologically important phenomenon: the susceptibility of serine proteases to nontransferrin-bound Fe3+.

Aniline Compounds↗
PubMed1982

Sialic acid dependent polypeptide chain heterogeneity of human fibrinogen demonstrated by two-dimensional electrophoresis.

Human fibrinogen was compared with asialofibrinogen by two-dimensional electrophoresis to evaluate the contribution of sialic acid to the heterogeneity of the gamma- and B beta-polypeptide chains. Reduced fibrinogen showed three major variants for both the gamma- and B beta-chains. In addition two minor gamma-bands with a more acidic isoelectric point than the normal gamma-chains were observed. Electrophoresis in the second dimension (SDS) suggests that these most acidic bands are gamma-chain-variants with a higher molecular weight. In asialofibrinogen only two predominant variants with more alkaline isoelectric points were present in each chain type. It is concluded that enzymatic removal of sialic acid partially reduced the heterogeneity of the gamma- and B beta-polypeptide chains of human fibrinogen, but additional sources producing charge heterogeneity must be sought.

Chemical Phenomena↗
PubMed1982

A subfraction of human fibrinogen with high sialic acid content and elongated gamma chains.

Fibrinogen isolated from normal human single donor or pool plasma was fractionated by DEAE-cellulose chromatography. Three different fibrinogen subfractions were obtained. The most acidic fraction comprising 22% of the whole fibrinogen pool was prominent by two special features: 1) its sialic acid content was significantly higher than that of bulk fibrinogen, namely 8 mol of sialic acid/mol of fibrinogen versus 6 mol in bulk fibrinogen. 2) Two-dimensional electrophoresis of the polypeptide chains obtained after reduction revealed a preferential accumulation in this subfraction of the elongated gamma chains previously described as gamma chain heterogeneity of whole human fibrinogen.

Chromatography, DEAE-Cellulose↗
PubMed1982

Thyroxine-rich iodopeptides as fragment of reduced guinea pig thyroglobulin.

Full reduction of guinea pig thyroglobulin with mercaptoethanol followed by polyacrylamide gel electrophoresis reveals the presence besides the well known three polypeptide chains, of small amounts of iodopeptides with a molecular weight of 3 000 to 46 000 daltons. One of these peptides with a molecular weight of roughly 10 000 daltons has a much higher efficiency to couple iodotyrosines into thyroxine than any other fragment of thyroglobulin. Despite its small quantity this peptide contributes more than one third to the total thyroxine synthesis from a given iodide shot at any time up to five days after its injection. Iodopeptides akin to that found in guinea pigs were recently described by several authors in different species. They probably represent the preferential domains for hormone synthesis within the intact thyroglobulin molecule.

Animals↗
PubMed1982

Comparison of 125I-fibrinogen kinetics and fibrinopeptide A in patients with disseminated neoplasias.

To provide more information on the pathways of fibrinogen catabolism in generalized cancer, the effect of heparin on fibrinopeptide A (fpA) and on 125I-fibrinogen kinetics was studied in 15 patients with disseminated neoplasia. Three patients had evidence of venous thrombosis and in 2 additional patients a low fibrinogen level together with increased amounts of FDP/fdp and a positive ethanol test indicated disseminated intravascular coagulation (DIC). The plasma levels of fpA were grossly elevated (4.6--20, mean 11.4 ng/ml, normal values 1.01 +/- 0.45 ng/ml) in patients with thrombosis or DIC, and normal to grossly elevated (0.4--10.4, mean 6.1 ng/ml) in the other patients. Intravenous heparin bolus lowered the fpA level in 11/11 patients, and continuous heparin treatment led to an impressive suppression or complete normalization of the plasma fpA in 5/6 patients. This finding is thought to reflect heparin suppression of thrombin activity on fibrinogen. In some cases, the fpA fall after heparin bolus was slow and/or incomplete, suggesting fpA generation at sites not easily accessible to heparin or insufficient heparin dosage. The 125I-fibrinogen kinetics were characterized by a significantly shorter half-life (t1/2: 2.5 days), increased catabolic rate constant (j: 0.44 days-1), and increased absolute turnover (68.9 mg fibrinogen/kg/day) as compared to 4 normal subjects (t1/2: 4.2 days; j: 0.26 days-1; turnover 21.7 mg fibrinogen/kg/day). As estimated from the fpA generation rates, intravascular thrombin action on fibrinogen contributed only in minor part to increase the turnover of 125I-fibrinogen. In particular, the turnover was greatly accelerated in heparin-treated patients despite impressive suppression or normalization of the fpA levels in 5/6 cases.

Adult↗
PubMed1981

[Fibrinogen Bern I and fibrinogen Bern II: 2 hereditary fibrinogen variants with diverse biochemical properties].

Two inherited fibrinogen variants, fibrinogen Bern I and fibrinogen Bern II, have been partially characterized. The markedly prolonged thrombin clotting times observed with both variants result from impaired fibrin monomer aggregation. Complete correction of this polymerization defect at physiological calcium concentrations has been achieved for fibrinogen Bern I. This variant also exhibits a charge abnormality in the gamma-polypeptide chain, an increased sialic acid content and defective calcium binding by the C-terminal part of the molecule. Fibrinogen Bern II, on the other hand, exhibits a defect which, although located at a site important for polymerization, is not influenced by the binding of calcium ions.

Binding Sites↗
PubMed1981

Reaccumulation of thyroglobulin and colloid in rat and mouse thyroid follicles during intense thyrotropin stimulation. A clue to the pathogenesis of colloid goiters.

Since Marine's observations some 50 years ago, it has been generally accepted that colloid goiters invariably result from colloid repletion of originally hyperplastic goiters after cessation of the goitrogenic stimulus. However, clinical observations suggest that many goiters never go through a stage of hyperplasia, but are colloid-rich from the beginning. We have injected rats and mice with thyrotropin (TSH), three times a day for 4 d, while the animals were kept on an iodine-rich diet (HID). Additional groups of animals were fed an iodine-poor diet (LID) or a diet containing 0.15% propylthiouracil (PTU) or 1% sodium perchlorate (ClO4). At intervals, thyroid weight, DNA, iodine and thyroglobulin content, thyroglobulin iodination, and intracellular droplet formation were measured. Histologic sections were also prepared and stained with periodic acid Schiff. Furthermore, thyroxine concentration was measured in the serum. Thyroglobulin content dropped by approximately 30% in HID animals but by 60% in all other groups 1 d after starting TSH. Thereafter, thyroglobulin reaccumulation occurred and droplet formation correspondingly decreased despite continuous heavy TSH stimulation. The largest amount of thyroglobulin was reaccumulated in HID animals followed by the PTU/LID groups, whereas no reaccumulation was observed in the ClO4 group. Reaccumulation of thyroglobulin only occurred if there was concomitant organification of at least some iodine. The subsequent phases of depletion and reaccumulation of thyroglobulin were mirrored by the morphology of the follicular lumina, the staining properties of the colloid and the serum T4 concentration. These observations suggest that endocytosis gradually becomes refractory to continuous TSH stimulation if a certain minimal amount of iodine is available for organic binding. Thus, primarily colloid-rich goiters may form in the presence of continuously higher than normal thyrotropin levels without a previous stage of follicular hyperplasia. The view should be revised that accumulation of colloid and intense thyrotropin stimulation are mutually exclusive events.

Animals↗
PubMed1981

Changes in the polypeptide assembly of guinea pig thyroglobulin induced by thyrotropin-regulated thyroid activity.

We have previously reported that the relative proportion of three polypeptide chains in guinea pig thyroglobulin is closely related to the iodine content of the protein. The present work demonstrates that it is not the iodine content per se but, rather, TSH-regulated thyroid activity which modulates the substructure of thyroglobulin. In a first set of experiments, the impact of TSH stimulation on sodium dodecyl sulfate (SDS)-induced dissociation of 19S thyroglobulin into 12S subunits was compared to that of iodination. While in control animals the ratio of 12S to 19S thyroglobulin was 48:52, it changed to 35:65 in glands strongly stimulated with TSH and blocked with MMI. This rise in the relative proportion of 19S thyroglobulin occurred despite a simultaneous drop of iodine content from 0.6% to 0.24%. It was only after TSH suppression that the well known inverse correlation between the level of iodination and dissociability reappeared. In a second set of experiments, SDS-treated thyroglobulin was fully reduced by splitting disulfide bonds with mercaptoethanol. In addition to the previously described three polypeptide chains, A, B, and C, a hitherto neglected nonreducible fraction comigrated with 19S thyroglobulin on polyacrylamide gels. Native thyroglobulin with widely varying iodine contents was obtained from unstimulated glands and from glands strongly stimulated with TSH. Drastic changes in the polypeptide chain assembly, depending on the degree of TSH stimulation but entirely independent of iodination, were observed. There was a strong negative correlation between the nonreducible 19S thyroglobulin fraction and both the B and C polypeptide chains with all experimental manipulations. We conclude that thyroglobulin substructure is highly dependent on the degree of TSH stimulation of the thyroid. TSH, through stimulation of unknown metabolic pathways, is a more important determinant of thyroglobulin substructure than the degree of iodination of the protein.

Animals↗
PubMed1980

Quantitative determination of fibrin and fibrinogen in biological material.

In order to measure quantitatively fibrin and fibrinogen in biological material such as thrombi, exudates, or tissues, the following method was developed and tested on model thrombi of different composition. Any fibrin and fibrinogen present is proteolytically degraded by endogenous and/or exogenous plasmin to their common late, soluble fragments D and E. Fragment E is determined by electroimmunoassay using a specific antiserum. From the amounts of fragment E the original fibrin(fibrinogen) antigen and thus of fibrin plus fibrinogen can be calculated on the basis of a molecular weight ratio of 340,000 for fibrinogen to 48,500 for fragment E. Purified fibrinogen degraded to fragments by plasmin resulted in a yield of 89.9% +/- 1.5 of the expected amount of fragment E. Fibrin under identical conditions resulted in a yield of 84.0% +/- 2.4, whereas crosslinked fibrin gave yields of 78.2% +/- 9.2 only after prolonged incubation. Control studies demonstrated that the presence of plasma proteins did not change the yield of fragment E. Measurement of the fibrin(fibrinogen) content of thrombotic material contained in surgically removed human aortic aneurysms demonstrated the validity and applicability of this method to biological material.

Antigens↗
PubMed1979

[The fibrin and plasma-protein content of human thrombi].

The protein composition of cell-free thrombus contained in abdominal aneurysms of the aorta was investigated using PAGE and immunoreactivity after solubilization. 1. The dry weight was 18--29%, with minor differences between various locations. 2. 35--40% of the dry weight was extractable with NaCl/citrate and was identified as albumin (80%) and IgG (15%). Trace amounts of fibrinogen immunoreactive material were present. 3. The NaCl/citrate insoluble part was 80% hydrolyzable with plasmin. The predominant fragment was D-D dimer (from cross-linked fibrin). In addition, fragments Dand E were observed. Reduction of the NaCl/citrate insoluble part with 2-mercaptoethanol resulted in almost complete solubilization. PAGE analysis demonstrated alpha-polmers, gamma-gamma dimers and little free alpha-chains, indicating almost complete cross-linking of fibrin. Thus, the major protein were cross-linked fibrin, albumin and IgG.

Aortic Aneurysm↗
PubMed1979

[Importance of the sialic acid moiety for the heterogeneity in human fibrinogen].

To determine whether the observed heterogeneity of gamma- and B beta-polypeptide chains of human fibrinogen (2 and 1 sialic acid residue per chain) is due to differences in sialic acid content, fibrinogen was desialatgen was compared with normal fibrinogen. The gamma-chain heterogeneity observed in normal fibrinogen was absent in asialofibrinogen, whereas the B beta-chain heterogeneity appeared to be unaffected. Although the variants were indistinguishable on SDS-PAGE, isoelectric focusing in the presence of urea demonstrated heterogeneities of both gamma- and B beta-cahins even in asialofibrinogen. However, fewer bands were recognized in asialofibrinogen. The difference in sialic acid content of the gamma- and B beta-chain variants of human fibrinogen therefore explains on part of the polypeptide chain heterogeneity.

Chromatography, Ion Exchange↗
PubMed1979

Low molecular weight intracellular iodocompounds with long intrathyroidal half-life: remnants of thyroglobulin hydrolysis?

In this paper additional information on low molecular weight, soluble, intrathyroidal iodocompounds with slow metabolic rate is provided. These compounds have previously been localized autoradiographically within the follicular cells. Radioiodide was administered to rats on a normal iodine intake (6--7 microgram/day) for 80 days to approach isotopic equilibration of the intrathyroidal iodine with the dietary radioiodide. When the isotope was omitted from the diet the intrathyroidal radioiodine was released with an apparent half-life of approximately 12 days. When the individual soluble components carrying radioiodine were analyzed after separation on Sephadex G-200, different apparent half-lives were found, the half-life of thyroglobulin (Tgb) being roughly 10 days and that of the low molecular weight iodocomounds being in the order of 60 to 100 days or more. In addition to the soluble low molecular weight iodocompounds, the radioactivity in the particulate fraction increased by 100% during the tracer washout when compared to Tgb and the total soluble fraction. The soluble slow turnover iodocompounds contained a higher percentage of carbohydrate and total iodine than Tgb, while the relative amounts of each sugar analyzed (hexoses, fucose, hexosamine and sialic acid) were close to those in Tgb. Sephadex G-25 chromatography of the low molecular weight iodocompounds obtained after Sephadex G-200 separation resulted in the separation of 4 peaks. Two peaks identified as iodopeptides could be further analyzed. The carbohydrate composition of these peptides was similar to that of 2 glycopeptides obtained after in vitro enzymatic hydrolysis of purified Tgb with pronase. Slow equilibration with radioiodine, long apparent intrathyroidal half-life and carbohydrate content similar to that of Tgb, taken together with previously published data on intracellular localization of soluble intrathyroidal iodocompounds, suggest that the low molecular weight iodocompounds are products of in vivo hydrolysis of engulfed Tgb droplets.

Animals↗
PubMed1978

Accumulation and localization of radiocalcium in the rat thyroid gland.

To determine the rate of accumulation of radiocalcium (45Ca) in the thyroid gland, the concentration of radiocalcium was measured in the blood serum and thyroid gland at various time intervals up to 7 days after a single ip injection of 45Ca in rats. The ratio of the 45Ca concentration in thyroid gland to serum (T:S) increased with the time interval after injection. Thyroid activity was varied by hypophysectomy or by feeding a low iodine diet with or without added thiouracil. The more active the gland, the faster it equilibrated with the serum 45Ca and the less was the T:S in the steady state. The equilibration was much slower than for radioiodide, taking several days in normal control rats and hours in very active glands. Autoradiographs showed that the 45Ca concentration was higher in association with the follicular epithelium than with the follicular lumen at 1 h or less after injection. However, at 24 h, the concentration of 45Ca was higher in the lumen than elsewhere in the gland. To determine rate constants describing the equilibration, the data in the normal gland were fitted with a model that took account of the differing rates of equilibration in cell and lumen. The presence of calcium in the lumen indicates that each time the follicular epithelial cell endocytosed stored luminal colloid before secretion, it also took in an appreciable amount of calcium.

Animals↗