Search PubMed⌕ Search

Biomedical subjects

P Friedrich

Publications and source records attributed to P Friedrich.

At least 91 records · Page 5Linked to original sources
PubMed1982

Interaction of ligands in phosphorylase A as monitored by crosslinking and enzymatic modifications: synergism of glucose and caffeine manifested in the exposure of N-terminal segment.

1. Glycogen, caffeine and glucose dissociate phosphorylase a tetramer to dimers with half-maximum effect at 0.16%, 1.1 and 71 mM concentration, respectively, as monitored by crosslinking with dimethyl suberimidate at 18 degrees C. 2. The above ligands increase the rate of dephosphorylation and tryptic digestion of phosphorylase alpha at 18 degrees C in the same way with half-maximum effect at 0.04%, 0.1 and 9 mM concentration, respectively. 3. Caffeine and glucose acted synergistically in tetramer dissociation as well as in the enzymic modifications. 4. The alpha-anomer of D-glucose was twice as effective as its mutarotational equilibrium solution.

Animals↗
PubMed1981

Localization of glyceraldehyde-3-phosphate dehydrogenase in intact human erythrocytes. Evaluation of membrane adherence is autoradiographs at low grain density.

Human erythrocytes were treated with highly tritiated [3H]iodoacetate under conditions when half of the label became attached to glyceraldehyde-3-phosphate dehydrogenase. After fixation, the cells were subjected to electron microscopic autoradiography. For the evaluation of distribution of grains, which were relatively few, a computerized method was developed. Statistical analysis of data showed the significant adherence of grains to the cell membrane. The results support the view that glyceraldehyde-3-phosphate dehydrogenase is localized near the membrane in the intact erythrocyte.

Erythrocyte Membrane↗
PubMed1981

Kinetic behaviour and oligomeric state of 3-phosphoglyceroyl-D-glyceraldehyde-3-phosphate dehydrogenase.

The specific activity of pig muscle D-glyceraldehyde-3-phosphate dehydrogenase was found to be constant in the reverse reaction, with NADH and 1,3-diphosphoglycerate as substrates, over the enzyme concentration range 10(-8) to 10(-4) M. The molecular weight of the covalent intermediate of the enzyme, 3-phosphoglyceroyl-glyceraldehyde-3-phosphate dehydrogenase, as measured by sedimentation techniques, proved constant (145 000 +/- 6 000) between 3 x 10(-5) M enzyme concentration. Likewise, no change in the apparent molecular weight was observed by gel-chromatography even at 2 x 10(-8) M enzyme concentration. The data indicate that the enzyme functions in its tetrameric form.

Animals↗
PubMed1980

Ca2+-induced conformational changes in the troponin complex detected by crosslinking.

In an attempt to detect Ca2+-induced conformational changes by crosslinking, rabbit muscle troponin complex was reacted with the bifunctional reagents 1,3-difluoro-4,6-dinitrobenzene, 4,4'-difluoro-3,3'-dinitrodiphenylsulfone and dimethyl suberimidate under various conditions and the products were analyzed by dodecyl sulfate gel electrophoresis. In the absence of divalent cations, with the two aromatic reagents at a low reagent/protein ratio, the main cross-link products were troponin T-I and I-C. With dimethyl suberimidate the only major crosslink product was conjugate T-I. Ca2+, alone as well as in the presence of Mg2+, prevented the formation of I-C crosslinks with both aromatic reagents, but it did not affect crosslinking with dimethyl suberimidate. Ca2+ also decreased the number of NH2 groups of troponin that are highly reactive towards 2,4,6-trinitrobenzene sulfonate. Both effects of Ca2+ can be interpreted in terms of a conformational change in the troponin complex elicited by the binding of the specific divalent cation.

Animals↗
PubMed1980

Identification of an intramolecular cross-link in troponin C after cross-linking the troponin complex with 1,3-difluoro-4,6-dinitrobenzene.

The troponin complex isolated from rabbit skeletal muscle was cross-linked with 1,3-difluoro-4,6-dinitrobenzene, subjected to tryptic hydrolysis, and the labelled peptides were separated. One peptide was purified to homogeneity; it proved to be peptide Gly(89)-Arg(100) of troponin C on the basis of amino acid composition and N-terminal analysis. The absorption spectrum of this peptide between 300 and 500 nm was very similar to that of 1-(S-cysteinyl)-5-(N epsilon-lysyl)-2,4-dinitrobenzene, which could only be due to cross-link formation between Lys-90 and Cys-98. This finding is interpreted in terms of the proposed tertiary structure of troponin C.

Chemical Phenomena↗
PubMed1980

Structural changes in glycogen phosphorylase as revealed by cross-linking with bifunctional diimidates: phospho-dephospho hybrid and phosphorylase a.

The technique of cross-linking with a series of bifunctional diimidates (maximal effective length ranging from 3.7 to 14.5 A), followed by dodecyl sulfate gel electrophoresis, was applied to compare the subunit contact areas of phosphorylases b, ab (the phospho-dephospho hybrid), and a and to study the structure and ligand-induced structural changes in phosphorylases ab and a. Similarly to phosphorylase b, the nearest cross-linkable lysyl-NH2 groups are about 3.7 A apart across the intradimer subunit interface (contact m) and about 8 A apart across the interdimer interface (contact d) in both phosphorylases ab and a. The activation of phosphorylase b induced by phosphorylation and that elicited by AMP binding are distinguishable at both contacts m and d. Phosphorylases ab and a tend to form tetramers whose structures are not identical, but AMP renders phosphorylase ab similar to phosphorylase a. Glucose, caffeine, and glycogen are able to dissociate both a and ab tetramers to dimers, whereas glucose 6-phosphate can only dissociate phosphorylase ab. The structure around the nucleotide site of phosphorylase a is rigid so that ligands binding here, such as AMP, ATP, ADP, inosine monophosphate, and glucose 6-phosphate, fail to influence the cross-link pattern. In control, in phosphorylase ab contact m is markedly affected by AMP, ATP, and glucose 1-phosphate; hence, in this respect phosphorylase ab resembles phosphorylase b.

Adenine Nucleotides↗
PubMed1979

The 'enzyme-probe' method for characterizing metabolite pools. The use of NAD-glycohydrolase in human erythrocyte sonicate as a model system.

1. An approach for testing the homogeneity of metabolite pools is described. An alien enzyme that can attack the metabolite in question is introducted into the system studied. By analyzing the time-course of decomposition of the metabolite it can be decided whether the pool is homogeneous in respect of reactivity towards the probe-enzyme or can be divided into fractions of different reactivities. 2. The information obtainable from such experiments is illustrated by the case of human erythrocyte sonicate as model system with NAD-glycohydrolase as probe-enzyme. The nicotinamide adenine dinucleotide pool in the concentrated sonicate could be resolved into three fractions (I, II and III) with half-lives of about 1, 7 and 240 min, respectively. Fraction I is free NAD, fraction II is NAD bound to glyceraldehyde-3-phosphate dehydrogenase, and fraction III is coenzyme strongly bound to some, so far unidentified, protein. Sonicate glycolysis seems to require only fraction II and is unable to use fraction III under the experimental conditions applied. 3. The scope of application of the enzyme-probe method is discussed.

Erythrocytes↗
PubMed1978

[The brain abscess today].

In spite of refined diagnostic and therapeutic possibilities, the cerebral abscess continues to be a disease involving great risks. A comparison of surgically treated groups of patients of the periods 1954 to 1962 and 1963 to 1977 does not show any reduction in lethality. This amounted to 15 per cent for the first group and 17.6 per cent for the second group. Extirpation of cerebral abscesses shows the most favourable results of treatment as compared to other surgical procedures. In our opinion, however, it will not remain the only method of treatment in future because it can only be employed if the patient is in a condition permitting an operation. That is why the open abscess treatment will continue to be justified for all cases where cerebral abscesses occur in combination with subdural or epidural empyemas. Certainly, modern anaesthesia methods as well as intensive pre- and postoperative therapy will further reduce the number of patients who are subjected to a primary puncture treatment. Since 1972, we have treated our patients exclusively by abscess exstirpations. Until 1977, none of the total number of 12 patients treated by us has died. We consider the use of scintigraphic and EEG controls of inflammatory cerebral processes to be of decisive importance. These controls enable a differentiation between diffuse and local inflammatory processes which are accompanied by a liquefaction and in this way permit the selection of the optimum time of operation. A basic condition, however, will always be a good interdisciplinary co-operation with infection departments, paediatric and ENT hospitals where in most cases patients suffering from brain abscesses are first admitted.

Adolescent↗
PubMed1977

[Experiences with hypophyseal adenoma patients].

UNLABELLED: The treatment of 126 patients presenting surgically treated and histologically determined suprasellar hypophyseal adenomas is described and the catamnesis followed up in some cases over a period of ten years after the transfrontal operation. Particular value is attached to a comparison of pre- and post-operative disturbances of acuity and field of vision. Moreover, the experience gained in the treatment of the first decade is compared with that of the second decade. CONCLUSIONS: I. The results of the treatment of a hypophyseal adenoma will be the better, the earlier it is detected. Disturbances of the gonadal function in particular can be traced back over many years. When primary or secondary amenorrhoea is present, gynaecologists should more often think of the existence of a hypophyseal adenoma. --2. The restoration of the working capacity of the patients operated on largely depends upon the restitution of the vision and an optimum hormonal substitution according to requirements. Thus, an early recognition of the lesion and the surgical method which must be further improved by employing modern techniques, are decisive.

Adenoma↗
PubMed1976

Crosslinking with bifunctional reagents as a means for studying the symmetry of oligomeric proteins.

A method based upon the principle that unlike domains of bonding are reflected in different reactivities and distribution of residues that can be crosslinked, has been elaborated for the determination of symmetry of oligomeric proteins. The derivation of theoretical curves for the prediction of crosslinking patterns of tetramers produced by reaction with a bifunctional reagent and subsequent sodium-dodecylsulphage-gel electrophoretic analysis, is presented. Based upon the theory the symmetry properties of a tetramer, to the extent whether it is an isologous or heterologous association, can be deduced by a simple calculation. Crosslinking patterns obtained with rabbit muscle aldolase and pig muscle lactate dehydrogenase after treatment with a series of diimidoesters of increasing chain length are evaluated and shown to be consistent with the expectations for isologous tetramers. From the patterns obtained with the various reagents the distances between lysyl residues located nearest to each other in different subunits in the two proteins could also be determined.

Actins↗