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Biomedical subjects

I Witt

Publications and source records attributed to I Witt.

At least 37 records · Page 2Linked to original sources
PubMed1991

Fibrinogen Kiel: a congenital dysfibrinogenaemia with (A alpha-16 Arg----His) substitution characterized by HPLC without prior isolation of fibrinogen.

A congenital fibrinogen variant in a German family is described which has been identified as a substitution of His in position 16 of the A alpha-chain for Arg, manifested over three generations in heterozygous form. The characterization is based on the reaction of the variant fibrinogen with thrombin and reptilase, on the HPLC-chromatographic properties and the amino acid composition of the abnormal fibrinopeptide A. Clinical observations in the affected family members (neither haemorrhagic nor thrombophilic tendencies), the results of routine coagulation tests (normal global clotting tests, prolonged thrombin and thrombin-coagulase time, decreased fibrinogen concentration in functional as opposed to immunological tests), and the autosomal co-dominant modus of inheritance of the fibrinogen variant are all in complete agreement with other reports in the literature concerning the same amino acid exchange. The results of our experiments with fibrinogen Kiel allow no definite conclusion regarding the question of whether it consists of pure homodimers or as of a mixture of homo- and heterodimers.

Amino Acids↗
PubMed1991

Test systems with synthetic peptide substrates in haemostaseology.

Since the early seventies, synthetic peptide substrates have been used in haemostaseology, enabling the introduction of photometry in coagulation analysis. Synthetic peptide substrates are short peptides (3-5 amino acid residues), with a chromogenic group coupled to the C-terminal end by an amide bond. The chromogenic group may be relatively specifically removed by proteases, and measured photometrically. By using the special properties of the many available substrates, test systems have been developed for procoagulant clotting factors, fibrinolytic factors, inhibitors of both systems and also for global tests of plasmatic coagulation. These tests can be performed manually or on automated analytical systems with high specificity, sensitivity and accuracy. The analytical advantages and new possibilities of the tests with chromogenic substrates have, in recent years, decisively stimulated not only haemostaseological basic research, but also clinical investigation and routine. Today, inhibitors of plasma coagulation (e.g. antithrombin III, protein C, C1-esterase inhibitor) as well as fibrinolytic parameters (e.g. tissue plasminogen activator, plasminogen activator inhibitor, alpha 2-antiplasmin) are nearly exclusively determined with chromogenic substrates. Further development will constitute the application of chromogenic substrates to "dry chemistry" methods.

Amino Acid Sequence↗
PubMed1990

Ischemic stroke due to protein C deficiency.

Plasma protein C exerts anticoagulatory effects by inactivating factors V and VIII. Hereditary protein C deficiency is transmitted as an autosomal dominant disorder. Homozygous individuals usually develop purpura fulminans as newborns; heterozygous protein C-deficient individuals are at increased risk for venous thrombosis and pulmonary embolism. However, arterial thrombosis has been only rarely observed. We describe a young patient with heterozygous protein C deficiency who experienced a severe stroke due to thrombotic occlusion of the left middle cerebral artery.

Adult↗
PubMed1990

[Inhibitors of blood coagulation in vascular occlusion of the retina and optic nerve].

The influence of a disturbed hemostasis as one of the causes of retinal or ciliary vascular occlusions is still controversial. Antithrombin III, protein C and its cofactor protein S were investigated in 25 patients; 14 of them with a retinal vein occlusion, five showed an occlusion of retinal arteries and six of ciliary arteries. Patients with a preceding thromboembolic disease were excluded from the investigations. The mean values (+/- SEM) of antithrombin III (12.1 IU/ml +/- 0.4), protein C (116% +/- 4), total protein S (102% +/- 3) and free protein S (46% +/- 2) were equivalent to the mean values of a normal population. Neither does a defect or a lack of coagulation inhibitors have an essential influence on the development of an isolated retinal or ciliary vascular occlusion nor does the local occlusive vascular disorder influence the activity of systemic inhibitors.

Aged↗
PubMed1987

Increase in the degree of phosphorylation of circulating fibrinogen under thrombolytic therapy with urokinase.

Human fibrinogen is phosphorylated in vivo to an equal extent at two positions, one at Ser 3 located on fibrinopeptide A, the other at Ser 345 of the A alpha-chain. As has been shown previously, the degree of phosphorylation of the circulating fibrinogen pool can be determined in vitro from the ratio between the HPLC peaks formed by phosphorylated and non-phosphorylated fibrinopeptide A which has been cleaved from plasma fibrinogen by thrombin or reptilase. Plasma samples were obtained from patients with venous thrombosis undergoing fibrinolytic therapy with urokinase (n = 8). The degree of phosphorylation increased from about 35% before treatment to values between 50% and 70% within 48 hours. It remained at these high levels as long as urokinase was administered and declined slowly thereafter. This behaviour of the degree of phosphorylation of fibrinogen is explained by a model which assumes that fibrinogen is secreted in the phosphorylated form and then dephosphorylated in the circulation by an up to now unidentified phosphatase by first order kinetics. When this system is in steady state, the degree of phosphorylation is about 25% under normal conditions. If the elimination rate of fibrinogen is greatly enhanced by fibrinogenolysis the system will approach a new steady state with a higher degree of phosphorylation, the magnitude of which will depend on the new ratio of dephosphorylation and elimination.

Blood Circulation↗
PubMed1985

Characterisation of calmodulin from Drosophila heads.

Calmodulin from Drosophila heads has been purified to apparent electrophoretic homogeneity. It has the same characteristics as bovine brain calmodulin with respect to the migration upon polyacrylamide gel electrophoresis and maximal activation of a calmodulin-deficient cAMP phosphodiesterase. The amino acid composition resembles bovine brain calmodulin with the exception that trimethyllysine is absent and that it contains only one tyrosine. The tryptic peptide map of Drosophila calmodulin suggests some differences in the amino acid sequence as compared to bovine brain calmodulin. These proposed differences in the primary structure may explain why Drosophila calmodulin is less potent than bovine brain calmodulin in the activation of a cAMP phosphodiesterase from bovine brain.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1985

Increased phosphorylation of human fibrinopeptide A under acute phase conditions.

The High Performance Liquid Chromatography (HPLC) separation of the fibrinopeptides liberated by the action of thrombin from plasma fibrinogen in a new one-step procedure without prior purification of fibrinogen is described. Since the phosphorylated and non-phosphorylated form of fibrinopeptide A are clearly resolved by this method, the determination of the degree of phosphorylation of fibrinopeptide A from the peak heights of these peptides becomes possible. By this method the degree of phosphorylation of fibrinogen in healthy volunteers (n = 21) is found to be 23.6 +/- 3.6%. Under acute phase conditions where the synthesis rate of fibrinogen is known to be markedly enhanced the degree of its phosphorylation also increases considerably. This was demonstrated on 13 patients undergoing an elective hip joint replacement, the hip surgery being chosen as a model for the elicitation of an acute phase reaction. The degree of phosphorylation rises steeply up to 60% on the first day after operation thereafter declining slowly to normal values within about one week. The maximum of the degree of phosphorylation precedes that of the fibrinogen concentration by several days. The mechanism which leads to the higher phosphorylation of fibrinogen during increased synthesis is unknown at the moment.

Chromatography, High Pressure Liquid↗
PubMed1985

NADPH-cytochrome P-450 reductase (pig liver). Studies on the sequence of the cyanogen bromide peptides from the catalytic domain and on the reactivity of the thiol groups.

The reactivity of the cysteine residues in the non-denatured catalytic domain of the NADPH-cytochrome P-450 reductase (pig liver) was studied using the -SH reagent monobromobimane. Prerequisite was the characterization of the cysteine residues by their surrounding amino-acid sequences. In pursuit of these aims the CNBr fragments obtained from the catalytic domain were sequenced. The cysteine residues are distributed on six CNBr fragments of the catalytic domain [Vogel and Lumper (1984) Hoppe-Seyler's Z. Physiol. Chem. 365, 1074]. Only the 11-kDa CNBr peptides with the N-terminal sequences Val-Gly-Pro-Thr- and Ala-Ser-Ser-Ser-, respectively, contain two cysteine residues each. The cysteine residues of the catalytic domain accessible to monobromobimane were localized on three CNBr peptides with the N-terminal sequences Val-Gly-Pro-Thr-, Ala-Ser-Ser-Ser- and Ala-Arg-Asp-Val-, respectively. Inactivation of the trypsin-solubilized enzyme by -SH-directed reagents is caused by the modification of the accessible cysteine residue (which can be protected by NADPH) in the 11-kDa CNBr fragment (N-terminal sequence: Val-Gly-Pro-Thr-). The cosubstrate NADPH protected a second cysteine residue localized in the 11-kDa CNBr peptide with the N-terminal sequence Ala-Ser-Ser-Ser-, which is however modified at a distinctly slower rate than the critical cysteine residue characterized by the sequence -Gly-Glu-Thr-Leu-Leu-Tyr-Tyr-Gly-Cys-Arg-Arg. Five non-reacting thiol groups were localized on CNBr fragments with the N-terminal sequences Val-Gly-Pro-Thr-, Ala-Ser-Ser-Ser-, Ser-Leu-Asn-Asn-, Gly-Lys-Tyr-Val-Asp- and Ala-Ala-Asp-Pro-.

Amino Acid Sequence↗
PubMed1984

The location of a second in vivo phosphorylation site in the A alpha-chain of human fibrinogen.

By quantitative phosphorus determination on the single chains of human fibrinogen it is demonstrated that the covalently bound phosphorus of adult and fetal fibrinogen is exclusively located in the A alpha chain. The A alpha-chain of fetal fibrinogen contains about twice as much phosphorus as the adult A alpha-chain in the well known position of Ser 3 of fibrino-peptide A as well as in a hitherto unknown second position on the A alpha-chain. By consecutive cleavage of the A alpha-chains of fetal and adult fibrinogen with cyanogen bromide, trypsin, and chymotrypsin, separation of the resulting peptide mixtures and analysis for phosphorylated amino acids, this second phosphorylation site could be traced to Ser 345 of the A alpha-chain. There is only one sequence homology between the two now known in vivo phosphorylation sites of human fibrinogen, namely that the second amino acid to the carboxyl side of the phosphorylated Ser is Glu. The sequence specificity of the up to now unidentified protein kinase phosphorylating fibrinogen allows it to be classified as a member of the group of type-2 casein kinases or casein kinases TS.

Amino Acid Sequence↗
PubMed1984

Isolation and complete amino-acid sequence of the small polypeptide from light-harvesting pigment-protein complex I (B870) of Rhodopseudomonas capsulata.

The small bacteriochlorophyll-binding polypeptide of the light-harvesting complex B870 was extracted from the intracytoplasmic membrane of the strain A1a+ of Rhodopseudomonas capsulata with chloroform/methanol/ammonium acetate and separated by chromatography on Sephadex LH60 using the same solvent. The polypeptide obtained from the peak fraction III was found to be homogeneous and identical with the small polypeptide isolated from the B870 complex as shown by dodecyl sulfate/polyacrylamide gel electrophoresis, amino acid composition and N-terminal sequence. The complete amino acid sequence is given. The relative molecular mass based on the amino acid sequence is 5341. The polarity of amino acids is 35.42%. The C-terminal part of the peptide chain from residue 29 to 48 is hydrophobic and includes one His residue.

Amino Acid Sequence↗
PubMed1984

Mandibular osteomas in familial polyposis coli.

Orthopantomograms of the mandible were performed on 46 patients with familial polyposis coli having no clinical signs of Gardner's syndrome and on 46 control patients matched according to age and sex. Thirty-five patients (76.1 per cent) and two (4.3 per cent) controls had osteomas (P less than 0.0005). It is concluded that orthopantomography of the mandible is a valuable diagnostic supplement to prophylactic proctosigmoidoscopic examination of first-degree relatives of polyposis patients. Due to the frequent occurrence of mandibular osteomas in polyposis patients without clinically detectable extracolonic manifestations, it is suggested that "Gardner's syndrome" is no longer considered a clinical entity.

Adolescent↗
PubMed1984

A comparative analysis of x-ray findings of the lumbar spine in patients with and without lumbar pain.

Roentgenograms of the lumbar spine from 238 patients with lower back pain (LBP) with sciatica were compared with roentgenograms from 66 patients without LBP. No difference between the two groups could be demonstrated concerning the incidence of spondylosis and disc degeneration. Cases with wedge-shaped vertebral bodies are significantly more frequent in patients younger than 40 years old in the group having pain. The incidence of spondylosis and disc degeneration increase with increasing age.

Adult↗
PubMed1984

The risk of developing breast cancer in relation to mammography findings.

Several studies have shown that it is possible to use the parenchymal patterns disclosed by mammography to differentiate various groups with a high risk of developing breast cancer. Accordingly, a patient series of 597 women who had undergone mammography during the period 1971-1975 was examined and classified according to Wolfe's system. A follow-up of 513 patients five to nine years after the mammography revealed no statistical difference in the tendency to develop breast cancer using Wolfe's parenchymal pattern method. The study shows that those in the group with pronounced fibroadenomatous changes, which were primarily studies radiologically, have an incidence of breast cancer three times as high as that found in the population as a whole.

Adult↗