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Biomedical subjects

W Junge

Publications and source records attributed to W Junge.

16 recordsLinked to original sources
PubMed1979

Identification of a non-specific carboxylesterase in human pancreas using vinyl 8-phenyloctanoate as a substrate.

Human pancreatic tissue, pancreatic juice and sera of patients suffering from acute pancreatitis contain a vinyl 8-phenyloctanoate hydrolysing activity which was separated from true pancreatic lipase (EC 3.1.1.3). The enzyme, preliminary called "non-specific pancreatic carboxylesterase, was partially purified from human pancreatic tissue by DEAE-cellulose chromatography. Its molecular weight was found to be 54 000 by gel filtration on Sephadex G-100. The isoelectric point was estimated as 4.65 by isoelectric focusing. The results explain the poor correlation obtained when determinations of "serum lipase activity" using triolein and vinyl 8-phenyloctanoate as substrates are compared. However, since non-specific pancreatic carboxylesterase is liberated into the serum, determination of this new enzyme provides additional information in the diagnosis of pancreatic diseases.

Caprylates↗
PubMed1979

Light-induced calcium release in isolated intact cattle rod outer segments upon photoexcitation of rhodopsin.

By applying flash-spectrophotometry with the calcium-indicating dye arsenazo III rapid light-triggered calcium release in various cattle rod outer segment preparations was studied. It is shown that light-induced calcium signals can be unambiguously discriminated from underlying absorption changes due to photolysis of rhodopsin and apparent absorption changes resulting from lightscattering transients. The following results have been obtained: 1. Calcium-induced arsenazo III responses can be quantitatively and kinetically resolved within the time domain of the visual transduction process. 2. Photoexcitation of rhodopsin results in calcium release from intradiscal binding sites. 3. Calcium released does not appear in the cytoplasmic space unless the disc membrane is made permeable to calcium ions by an ionophore. 4. The shortest observed half-rise time of calcium release (300 ms) is possibly limited by the ionophore. 5. The stoichiometric ratio of calcium released/rhodopsin bleached is 0.5 at a free calcium concentration of 2 microM. The amount of calcium released is proportional to the precentage of rhodopsin bleaching (from 1--10%). 6. Upon disruption of the disc stack by lysis of intact rod outer segments the light-induced calcium release is greatly altered. The results are discussed in relation to previous reports on a light-induced calcium release from retinal discs and in terms of the proposed role of calcium as an intracellular transmitter in vertebrate photoreceptors.

Animals↗
PubMed1979

The buffering capacity of the internal phase of thylakoids and the magnitude of the pH changes inside under flashing light.

The buffering capacity inside thylakoids is determined and the magnitude of flash-induced pH changes inside is calibrated in the pH range from 6.4 to 8.1. The work is based on flash-induced absorption changes of neutral red in a chloroplast suspension in which the outer phase is strongly buffered by bovine serum albumin. It is shown that neutral red is bound inside thylakoids. The binding can be described by a simple isotherm with an apparent Km = 4 microM and satruation at 1 neutral red per 17 chlorophylls. The apparent pK of neutral red is shifted from 6.6 in solution to 7.25 when bound inside. It is demonstrated that neutral red is a clean indicator of pH changes inside, i.e. when properly used it shows no response to other events. Although bound it reports pH changes which occur in the internal osmolar (aqueous) volume of thylakoids. This is obvious from the influence of chemically very different buffers on the magnitude of the absorption changes of neutral red. These act in a manner proportional to their calculated buffering capacity in aqueous solution. The intrinsic buffering capacity of the internal phase is determined with the aid of these buffers, at pH 7.2 it is between 0.8 and 1 mM (at 60 mosM). The absence of large variations in the buffering capacity in the range from pH 6.4 to 8.1 suggests that proteinaceous groups are involved in addition to the lipids which may dominate the buffering capacity at lower pH. The magnitude of the internal pH change is arrpox. 0.6 (at pH 7.3) under stimulation of both photosystems with a short xenon flash of light.

Chloroplasts↗
PubMed1979

Characterization of the isoenzymes of pig-liver esterase. 1. Chemical Studies.

Three different subunits of highly purified pig liver esterase (EC 3.1.1.1) can be separated by analytical dodecyl sulfate electrophoresis, though their relative mobilities are very similar. The same subunit bands are obtained with microsomes, in which the esterases have been labeled with the specific active-site-directed inhibitor bis(4-nitro-[14C]phenyl)phosphate. The heterogeneity of the native trimeric enzyme is much more complex, as is demonstrated by isoelectric focussing and polyacrylamide gel electrophoresis. Fractions of esterase which were partially separated by preparative isoelectric focussing show differences in their subunit composition, their amino acid analyses, their tryptic peptide maps, and their C-terminal amino acids. From these experiments various features of the differing esterase subunits can be deduced. Based on the chemical results and on various experiments which did not indicate any secondary modification of the protein side-chains, the molecular basis of the esterase heterogeneity is discussed. We conclude that the native trimeric esterase is a mixture of numerous hybrids of at least three protein subunits with differing but closely related primary sequences. A comparison of the relative specificity of various preparations of pig liver microsomes indicates that genetic differences concerning the composition of liver esterase exist between individuals.

Amino Acids↗
PubMed1978

[Haptoglobin phenotypes and liver cirrhosis. I (author's transl)].

The distribution of haptoglobin phenotypes (Hp) 1--1, 2--1 and 2--2 in 174 patients suffering from liver cirrhosis was determined and compared with a reference group consisting of 194 healthy subjects. The study revealed a high frequency of the Hp 1--1 phenotype (32%) in the patients as compared with the control group (14%). This difference is statistically highly significant (p less than 0.00025). It was calculated that in individuals of type Hp 1--1, the risk of liver cirrhosis is 4.3-fold higher than in persons with the phenotype Hp 2--2.

Adolescent↗
PubMed1978

[Fluorescent antibody technique in identification of Neisseria gonorrhoeae-microcolonies grown on membrane filters (author's transl)].

Filter membranes (Nucleopore, No. N060, CPR 01300, pore size 0.6 mu) are inoculated with a pure suspension of N. gonorrhoeae or a Urethral smear from patients suffering from gonococcal urethritis. The membranes are placed on chocolate agar and incubated for three hours. After fixation in formaldehyd, grown microcolonies of N. gonorrhoea are detected microscopically after incubation of the membranes with a fluorescein-isothiocyanate labeled gonococcal antiserum (Difco, charge no. 605907) (Fig. 3--5). The high specificity of the antiserum was shown by lack of reaction with various other neisseriae (except for N. meningitidis, which showed a weak positive reaction) or other bacteria, respectively (table 1). To investigate the reliability of the new method urethral smears of 23 patients suffering from acute or chronic gonorrhoea were examined by culturing for gonococci in the conventional way and by means of the new technique. In all cases gonocococci were detected with both methods. This suggests that the fluorescent antibody technique has at least the same sensibility as the conventional one, and has the advantage that the result is obtained within one day.

Acute Disease↗
PubMed1977

Gated proton conduction via the coupling factor of photophosphorylation modified by N,-N-orthophenyldimaleimide.

The membrane bound coupling factor of photophosphorylation is studied after pretreatment of broken chloroplasts with the bifunctional N,N-orthophenyldimaleimide under energization of the thylakoid membrane by mild flashing light. The proton conduction of the membrane is monitored both via the electrochromic absorption changes and via selective pH-indicating dyes. It is found that the coupling factor, after interaction with N,N-orthophenyldimaleimide during the preillumination period, shortcircuits one of the two protons pumped inside after excitation of chloroplasts with one short flash of light. In contrast to the low proton conductivity of the unperturbed thylakoid membrane (relaxation time for a proton gradient greater than 5s), this extra proton channel leads to a partial relaxation of a proton gradient within a few ms. Although limited to only one proton per electron, this extra proton conducting pathway is not otherwise specific. It operates with protons resulting from both Photosystem I and Photosystem II activity. In addition it operates with protons already present in the internal phase before firing of the exciting light flash. These effects are prevented by the presence of ATP (but not GTP) during the preillumination period. It is suggested that the modified coupling factor is gated open by the light induced electric field across the thylakoid membrane while self closing after passage of one proton per activated coupling factor.

Chemical Phenomena↗
PubMed1976

The coupling factor of photophosphorylation and the electric properties of the thylakoid membrane.

The rate of ATP synthesis of illuminated chloroplasts is correlated with the electric conductance of their inner membranes. In agreement with previous studies it is shown that ATP synthesis is paralleled by an increased conductance of the thylakoid membrane. This conductance together with the ability to form ATP is abolished if chloroplasts are treated with an antibody against the coupling factor CF1. It is not influenced by the fragmented monovalent antibody. This parallels the lack of influence of the fragmented antibody on ATP synthesis in contrast to its influence on hydrolysis and exchange reactions. We conclude that there are different sites for the interaction of the coupling factor with adenine nucleotides. Extraction of the coupling factor is shown to increase the membrane conductance by more than two orders of magnitude. Reincorporation of the crude coupling factor partially restores the net conductance of the membrane (increase in resistance by a factor of 2.5), while a higher degree of restoration was observed for ATP synthesis and the proton conductivity of the membrane. We conclude that the extraction procedure opens different conductive channels in the membrane; a proton specific one, possibly associated with the binding protein for the coupling factor, plus other channels for "non-protons" which in contrast to the proton channel cannot be plugged by reincorporation of the coupling factor.

Adenosine Triphosphate↗
PubMed1975

Symmetry, orientation and rotational mobility in the a3 heme of cytochrome c oxidase in the inner membrane of mitochondria.

The photoinduced linear dichroism of absorption changes resulting from photolysis of the complex between heme a3 of the cytochrome oxidase and CO is studied. The experiments started from isotropic solutions or suspensions of the enzyme both in its isolated form and in mitochondria. The anisotropy responsible for the linear dichroism was induced by excitation with a flash of linearly polarized light. The dichroic ratios observed with various systems; polymerized enzyme in solution, enzyme in mitochondria and in submitochondrial particles (at 20 degrees C as well as at liquid N2-temperature) all approached a value of 4/3 which characterizes a chromophore which is circularly degenerate. Therefrom we conclude that the interaction of heme a3 with its microenvironment within the protein does not break its four-fold symmetry. The experiments with mitochondria and submitochondrial particles suspended in aqueous buffer revealed similarly high dichoric ratios without any dichroic relaxation other than a rather slow one which could be attributed to the rotation of the whole organelle in the suspending medium. Therefrom we conclude that the cytochrome oxidase either is totally immobilized in the membrane, or that it carries out only limited rotational diffusion around a single axis coinciding with the symmetry axis of heme a3. In the light of independent evidence for a transmembrane arrangement of the oxidase and for the general fluidity of the inner mitochondrial membrane we consider anisotropic mobility of the cytochrome oxidase around an axis normal to the plane of the membrane as the most likely interpretation. Then our experimental results imply that the plane of heme a3 is coplanar to the membrane.

Animals↗
PubMed1975

[Possibilities of differenciating mycoplasma serologically and by protein analysis (author's transl)].

The problem of serological differentiation of the various mycoplasma strains and their demarcation from the L-phase variants of bacteria are based on the fact that it is difficult to obtain highly purified antisera which are only directed towards the cell membrane. For this reason an attempt was made by means of diselectrophoresis to determine the plasma and membrane proteins of various mycoplasma strains and L-phase variants and to evaluate them from differential diagnostic point of view. The results suggest that an unequivocal and rational differentiation is possible by this method of examination.

Antibodies, Bacterial↗
PubMed1975

Current-voltage studies on the thylakoid membrane in the presence of ionophores.

The reversibility of the binding of ionophores to the thylakoid membrane is studied. While gramicidin binds practically irreversibly, valinomycin and nonactin bind reversibly, however, only a small fraction (about 1%) of the membrane-bound valinomycin or nonactin is active in ion transport. The current-voltage relationship is evaluated under these circumstances. We have found that it is practically linear. This together with the relationship between current and ion concentration agrees qualitatively with the results reported for bimolecular lipid membranes, which contain a large fraction of negatively charged lipids. For the ionophores, valinomycin and nonactin, the binding equilibria (K approximately equal to 10-4) and the turnover numbers (approximately equal to 3-10-4/s) are evaluated for their action on the thylakoid membrane. Possible reasons for the inactivity of the majority of membrane-bound ionophore molecules are discussed.

Anti-Bacterial Agents↗
PubMedDate not supplied

The field of possible structures for the chlorophyll a dimer in photosystem I of green plants delineated by polarized photochemistry.

Photoselection experiments with immobilized photosystem I particles have been done to determine the mutual orientation of pigments in the reaction centre. When these particles are excited and interrogated with linearly polarized light, the flash-induced transient absorption changes (mainly from the chlorophyll a dimer) reveal linear dichroism, which yields information on the mutual orientation between the excited and the interrogated transition moments. The interpretation of the data, however, is ambiguous, (1) for reasons of principles inherent in the photoselection technique when applied to complex systems and (2) because of incomplete knowledge about the relative contribution of x- and of y-polarized transitions of chlorophyll a to absorption or to absorption changes at a given wavelength. We find it impossible to attribute any particular structure to the photooxidizable dimer based on photoselection data alone. Instead we present a field of possible structures, imposing constraints on proposed models for the dimer structure.

Chlorophyll↗