Biomedical subjects

W Junge

Publications and source records attributed to W Junge.

At least 73 records · Page 4Linked to original sources

PubMed1992

Renal tolerance of gadolinium-DTPA/dimeglumine in patients with chronic renal failure.

Safety data for renal tolerance of gadolinium-DTPA(Gd-DTPA)/dimeglumine were evaluated in 21 patients (age: mean +/- standard deviation [SD], 58 +/- 12 years) with impaired renal function. The mean +/- SD serum creatinine level at baseline was 213 +/- 101 mumol/L (range, 89.2-551 mumol/L). Creatinine clearance at baseline averaged 34.5 +/- 19.2 mL/minute (range, 7.2-70 mL/minute). Gd-DTPA was injected at a dose of 0.1 mmol/kg body weight. Serum parameters (creatinine, sodium, and potassium) were determined before and 6, 24, 48, and 120 hours after administration of Gd-DTPA. Urinary parameters (N-acetyl-beta-D-glucosaminidase [beta-NAG], protein, and albumin) were determined before (spot urine sample) and after treatment for collection periods 0 to 3, 3 to 6, 6 to 12, 12 to 24, and 24 to 48 hours. A final spot urine sample was taken at 120 hours. There was no significant statistical change of serum creatinine level within the observation period, and there was no single patient matching the criteria of acute renal failure (increase of serum creatinine level of 88.4 mumol/L [1 mg/dL] or more within 48 hours after injection). Serum values of sodium and potassium levels remained unchanged. Beta-NAG was slightly increased 0 to 3 hours after injection, but returned to baseline values during the collection periods up to 120 hours. There was no increase of protein or albumin excretion. These preliminary results suggest Gd-DTPA has good renal tolerance in patients with pre-existing chronic renal failure.

Adult↗

PubMed1991

[Determination of beta-N-acetylglucosaminidase and albumin in urine: comparison of methods and effect of gel filtration in human and rat urine].

A new kinetic method for determination of beta-N-acetylglucosaminidase (beta-NAG, EC 3.2.1.30) in human and rat urine with chlorophenol red-NAG as substrate is compared to two other methods with 4-nitrophenyl-NAG and 3-cresol-sulfonphthaleinyl-NAG respectively as substrates. The impact of gel filtration of urinary specimens on the determination of beta-NAG-activity and of low albumin concentrations in urine is described.

Acetylglucosaminidase↗

PubMed1990

The electric unit size of thylakoid membranes.

The size of the function unit of electrical events in thylakoid membranes was estimated by the minimum amount of gramicidin needed to discharge the flash light generated electrical potential difference. Early flash spectroscopic measurements have indicated that a single gramicidin dimer operates on an electrical function unit containing at least 2 x 10(5) chlorophyll molecules. In this study we present gramicidin titrations with more intact thylakoid preparations which revealed a more than hundred-fold greater lower limit for the electric unit size, namely 5 x 10(7) chlorophyll molecules. It is conceivable that the whole complicated thylakoid structure inside a chloroplast constitutes a single electric unit. It comprises more than 2 x 10(8) chlorophyll molecules in an area of more than 400 microns 2.

Cell-Free System↗

PubMed1990

Dicyclohexylcarbodiimide-binding proteins related to the short circuit of the proton-pumping activity of photosystem II. Identified as light-harvesting chlorophyll-a/b-binding proteins.

In photosynthesis of higher plants, photosystem II drives electron transfer from the water-oxidizing manganese centre at the lumenal side to bound plastoquinone at the stromal side of the thylakoid membrane. Proton release into the lumen and proton uptake from the stroma, i.e. net proton pumping, follows as consequence of vectoral electron transport. The proton pumping activity can be short circuited by covalent modification with N,N'-dicyclohexylcarbodiimide (cHxN)2C of certain proteins in the 20-28-kDa range. After modification, protons from water oxidation are no longer released into the thylakoid lumen, but instead transferred through the photosystem complex to protonate the photoreduced bound quinone at the other side of the membrane [Jahns, P., Polle, A. & Junge, W. (1988) EMBO J. 7, 589-594]. Here we identify the pertinent (cHxN)2C-binding proteins by amino acid sequence analysis and localize (cHxN)2C-binding sites within their primary structure. The proteins that are associated with the proton short circuit are light-harvesting chlorophyll-a/b-binding proteins. Our results imply that in addition to acting as antennae they may serve another function: the funneling into the thylakoid lumen of protons, which are liberated in the water-oxidizing Mn centre.

Amino Acid Sequence↗

PubMed1990

Reconstitution of photophosphorylation in EDTA-treated thylakoids by added chloroplast coupling factor 1 (ATPase) and chloroplast coupling factor 1 lacking the delta subunit. Structural or functional?

Upon EDTA treatment thylakoids lose the chloroplast coupling factor 1 (CF1) part of their ATP synthase, CF0CF1, this exposes the proton channel, CF0. The previously established ability of the CF1 subunit delta to block the proton leak through CF0 prompted us to study (a) the ability of complete CF1 and, for comparison, CF1 lacking the delta subunit to block proton leakage and thereby to reconstitute structurally some photophosphorylation activity of the remaining CF0CF1 molecules and (b) their ability to form functional enzymes (functional reconstitution). In order to discriminate between activities caused by added CF1 or CF1(-delta) and remaining CF0CF1, the former were inhibited by chemical modification of subunit beta by N,N'-dicyclohexyl carbodiimide (DCCD) and the latter by tentoxin. We found that added CF1 acted both structurally and functionally while added DCCD-treated CF1 (DCCD-CF1) acted only structurally. In contrast to previous observations, CF1(-delta) and DCCD-CF1(-delta) also acted structurally although the reduction of proton leakage was smaller than with DCCD-CF1. Hence there was no functional reconstitution without subunit delta present. Previous studies indicated that only a small fraction of exposed CF0 is highly conducting and that this small fraction is distinguished by its high affinity for added CF1. The results of this study point rather to a wider distribution of CF0 conductance states and binding affinities.

Cell-Free System↗

PubMed1990

Subunit delta of H(+)-ATPases: at the interface between proton flow and ATP synthesis.

The ATP synthases in photophosphorylation and respiration are of the F-type with a membrane-bound proton channel, F0, and an extrinsic catalytic portion, F1. The properties of one particular subunit, delta (in chloroplasts and Escherichia coli) and OSCP (in mitochondria), are reviewed and the role of this subunit at the interface between F0 and F1 is discussed. Delta and OSCP from the three sources have in common the molecular mass (approximately 20 kDa), an elongated shape (axial ratio in solution about 3:1), one high-affinity binding site to F1 (Kd approximately 100 nM) plus probably one or two further low-affinity sites. When isolated delta is added to CF1-depleted thylakoid membranes, it can block proton flow through exposed CF0 channels, as do CF1 or CF1(-delta)+ delta. This identifies delta as part of the proton conductor or, alternatively, conformational energy transducer between F0 (proton flow) and F1 (ATP). Hybrid constructs as CF1(-delta)+ E. coli delta and EF1(-delta)+ chloroplast delta diminish proton flow through CF0.CF1(-delta) + E. coli delta does the same on EF0. Impairment of proton leaks either through CF0 or through EF0 causes "structural reconstitution' of ATP synthesis by remaining intact F0F1. Functional reconstitution (ATP synthesis by fully reconstructed F0F1), however, is absolutely dependent on the presence of subunit delta and is therefore observed only with CF1 or CF1(-delta) + chloroplast delta on CF0 and EF1 or EF1(-delta) + E. coli delta on EF0. The effect of hybrid constructs on F0 channels is surprising in view of the limited sequence homology between chloroplast and E. coli delta (36% conserved residues including conservative replacements). An analysis of the distribution of the conserved residues at present does not allow us to discriminate between the postulated conformational or proton-conductive roles of subunit delta.

Adenosine Triphosphatases↗

PubMed1990

[In vitro studies of the adsorption behavior of Wofatit Y 88 in relation to various drugs].

The adsorber Wofatit Y 88 (VEB Chemiekombinat Bitterfeld) was tested regarding its adsorption properties in comparison with Hämoresin (B. Braun, Melsungen, FRG) Hemosorbent SKN-2K (USSR) and the own product Wofatit UH 91. As adsorptives the hypnotics Metaqualon, Pyrithyldion, Crotylbarbital and Phenobarbital were used. The investigation have been performed in a single-pass system in a relation of 1:25 to the clinical practice conditions. The concentration measurements to the estimation of adsorbed amounts were made by UV-VIS spectrometry. It was found that Wofatit Y 88 is superior to Hämoresin with regard to adsorbed amounts and adsorption speed. For all drugs Wofatit Y 88 was superior to UH 91.

Adsorption↗

PubMed1989

Cross-reconstitution of the F0F1-ATP synthases of chloroplasts and Escherichia coli with special emphasis on subunit delta.

F0F1-ATP synthases catalyse ATP formation from ADP and Pi by using the free energy supplied by the transmembrane electrochemical potential of the proton. The delta subunit of F1 plays an important role at the interface between the channel portion F0 and the catalytic portion F1. In chloroplasts it can plug the protonic conductance of CF0 and in Escherichia coli it is required for binding of EF1 to EF0. We wanted to know whether or not delta of one species was effective between F0 and F1 of the other species and vice versa. To this end the respective coupling membrane (thylakoids, everted vesicles from E. coli) was (partially) depleted of F1 and purified F1, F1(-delta), and delta were added in various combinations to the F1-depleted membranes. The efficiency or reconstitution was measured in thylakoids via the rate of phenazinemethosulfate-mediated cyclic photophosphorylation and in E. coli everted vesicles via the degree of 9-amino-6-chloro-2-methoxyacridine fluorescence quenching. Addition of CF1 to partially CF1-depleted thylakoid vesicles restored photophosphorylation to the highest extent. CF1(-delta)+chloroplast delta, EF1, EF1(-delta)+E. coli delta were also effective but to lesser extent. CF1(-delta)+E. coli delta and EF1(-delta)+chloroplast delta restored photophosphorylation to a small but still significant extent. With F1-depleted everted vesicles prepared by repeated EDTA treatment of E. coli membranes, addition of CF1, CF1 (-delta)+chloroplast delta and CF1(-delta)+E. coli delta gave approximately half the extent of 9-amino-6-chloro-2-methoxyacridine fluorescence quenching as compared to EF1 or EF1(-delta)+E. coli delta by energization of the vesicles with NADH, while Ef1(-delta)+chloroplast delta was ineffective. All 'mixed' combinations were probably reconstitutively active only by plugging the protonic leak through the exposed F0 (structural reconstitution) rather than by catalytic activity. Nevertheless, the cross-reconstitution is stunning in view of the weak sequence similarity between chloroplast delta and E. coli delta. It favors a role of delta as a conformational transducer rather than as a proton conductor between F0 and F1.

Chloroplasts↗

PubMed1989

CF0, the proton channel of chloroplast ATP synthase. After removal of CF1 it appears in two forms with highly different proton conductance.

The discharge of the flash-induced transmembrane voltage through the exposed proton channel, CF0, of the chloroplast ATP synthase, CF0CF1 was investigated. EDTA treatment of thylakoid membranes exposed approximately 50% of total CF0 by removal of the CF1 counterparts. This greatly accelerated the decay of the transmembrane voltage, as was apparent from electrochromic-absorption changes of intrinsic pigments and by pH-indicating-absorption changes of added dyes. Two decay processes were discernible, one rapid with a typical half-decay time of 2 ms, and a slower one with a half-decay time variable between 20-100 ms. Both were sensitive to CF0 inhibitors, but only the rapid decay process was also inhibited by added CF1. CF1 was effective in surprisingly small amounts, which were significantly lower than those previously removed by EDTA treatment. This finding corroborated our previous conclusion that the rapid decay of the transmembrane voltage was attributable to only a few high-conductance channels among many CF0 molecules, typically in the order of one channel/CF1-depleted EDTA vesicle. Inhibition of photophosphorylation in control thylakoids was measured as function of the concentration of CF0 inhibitors. It was compared with the inhibition of proton conduction through exposed CF0 in EDTA vesicles. Photophosphorylation and proton conduction by the high-conductance form of CF0 were inhibited by the same low inhibitor concentrations. This suggested that the high-conducting form of CF0 with a time-averaged single-channel conductance of 1 pS [Lill, H., Althoff, G. & Junge, W. (1987) J. Membrane Biol. 98, 69-78] represented the proton channel in the integral enzyme, which acted as a low-impedance access from the thylakoid lumen to the coupling site in CF0CF1. The slow decay process was attributed to a majority of low-conductance CF0 channels, i.e. about 50 molecules/vesicle. The conductance of these channels was more than 100-fold lower and they did not compete with the very few highly conducting channels for rebinding of added CF1. The low proton conduction of the majority of exposed CF0 molecules, possibly due to a structural rearrangement, may be protecting the thylakoid membrane against rapid energy dissipation caused by accidental loss of CF1. It may also explain the low single-channel conductance of bacterial F0 reported in the literature.

Binding Sites↗

PubMed1989

Chloroplast ATP synthase contains one single copy of subunit delta that is indispensable for photophosphorylation.

F0F1 ATP synthases synthesize ATP in their F1 portion at the expense of free energy supplied by proton flow which enters the enzyme through their channel portion F0. The smaller subunits of F1, especially subunit delta, may act as energy transducers between these rather distant functional units. We have previously shown that chloroplast delta, when added to thylakoids partially depleted of the coupling factor CF1, can reconstitute photophosphorylation by inhibiting proton leakage through exposed coupling factor CF0. In view of controversies in the literature, we reinvestigated two further aspects related to subunit delta, namely (a) its stoichiometry in CF0CF1 and (b) whether or not delta is required for photophosphorylation. By rocket immunoelectrophoresis of thylakoid membranes and calibration against purified delta, we confirmed a stoichiometry of one delta per CF0CF1. In CF1-depleted thylakoids photophosphorylation could be reconstituted not only by adding CF1 and subunit delta but, surprisingly, also by CF1 (-delta). We found that the latter was attributable to a contamination of CF1 (-delta) preparations with integral CF1. To lesser extent CF1 (-delta) acted by complementary rebinding to CF0 channels that were closed because they contained delta [CF0(+delta)]. This added catalytic capacity to proton-tight thylakoid vesicles. The ability of subunit delta to control proton flow through CF0 and the absolute requirement for delta in restoration of photophosphorylation suggest an essential role of this small subunit at the interface between the large portions of ATP synthase: delta may be part of the coupling site between electrochemical, conformational and chemical events in this enzyme.

Amino Acids↗

PubMed1989

Evaluation of a new assay for pancreatic amylase: performance characteristics and estimation of reference intervals.

We have evaluated a new assay for the specific determination of pancreatic (P) isoamylase, the principle being based on a synergistic inhibitory effect of two monoclonal antibodies directed towards salivary (S) amylase. After 3 min incubation, activities were determined with maltoheptaoside-PNP as substrate on a Hitachi 705 analyzer at 25, 30 and 37 degrees C, respectively. Coefficients of variation ranged from 0.6 to 5.4% for within-run and 2.1 to 9.9% for day-to-day precision. Linearity held up to 1200 U/L (25 degrees C) and 2300 U/L (37 degrees C). Comparison of the new method with the wheat germ inhibitor technique showed an excellent correlation, with coefficients ranging from 0.990 to 1.00. Using purified P- and S-amylase we observed no inhibiting cross-reactivity of the antibodies with the P-isoenzyme, but an incomplete blockage of S-amylase: residual activity was approximately 2% at 25 and 30 degrees C, and 2.5% at 37 degrees C. The distribution pattern of P-, S- and total amylase activity in serum of healthy subjects was only slightly skewed to the right. We found neither an influence of sex nor of age on the reference ranges. In random urine samples, distribution of activities was strongly skewed. However, if the activity was related to the urinary creatinine concentration, an approximately normal distribution was obtained, allowing, as in serum, the establishment of upper and lower reference values.

Adolescent↗

PubMed1989

Protons, the thylakoid membrane, and the chloroplast ATP synthase.

According to the chemiosmotic theory, proton pumps and ATP synthases are coupled by lateral proton flow through aqueous phases. Three long-standing challenges to this concept, all of which have been loosely subsumed under 'localized coupling' in the literature, were examined in the light of experiments carried out with thylakoids: (1) Nearest neighbor interaction between pumps and ATP synthases. Considering the large distances between photosystem II and CFoCF1, in stacked thylakoids this is a priori absent. (2) Enhanced proton diffusion along the surface of the membrane. This could not be substantiated for the outer side of the thylakoid membrane. Even for the interface between pure lipid and water, two laboratories have reported the absence of enhanced diffusion. (3) Localized proton ducts in the membrane. Intramembrane domains that can transiently trap protons do exist in thylakoid membranes, but because of their limited storage capacity for protons, they probably do not matter for photophosphorylation under continuous light. Seemingly in favor of localized proton ducts is the failure of a supposedly permeant buffer to enhance the onset lag of photophosphorylation. However, it was found that failure of some buffers and the ability of others in this respect were correlated with their failure/ability to quench pH transients in the thylakoid lumen, as predicted by the chemiosmotic theory. It was shown that the chemiosmotic concept is a fair approximation, even for narrow aqueous phases, as in stacked thylakoids. These are approximately isopotential, and protons are taken in by the ATP synthase straight from the lumen. The molecular mechanism by which F0F1 ATPases couple proton flow to ATP synthesis is still unknown. The threefold structural symmetry of the headpiece that, probably, finds a corollary in the channel portion of these enzymes appeals to the common wisdom that structural symmetry causes functional symmetry. "Rotation catalysis" has been proposed. It is of heuristic value to visualize CFoCF1 as a mechanical coupling device. Its maximum turnover number ranges up to 400 s-1 for ATP and 1200 s-1 for protons. At about 200 mV electric driving force this implied a conductance of about 1 fS. Its channel portion (CFo), however, has revealed a very large protonic conductance of 1 pS (three orders of magnitude greater than the protonic conductance of gramicidin around neutral pH). (6) The sight and smell of food increased LH serotonin release; this effect was detectable when local fluoxetine was used to block serotonin reuptake.(ABSTRACT TRUNCATED AT 400 WORDS)

Biological Transport↗

PubMed1989

Prevention of radiocontrast-media-induced nephrotoxicity by the calcium channel blocker nitrendipine: a prospective randomised clinical trial.

Despite the development of new non-ionic low-osmolality contrast media, nephrotoxicity of intravascular radio-opaque contrast media remains a severe clinical problem, particularly in patients with risk factors. Widely accepted mechanisms of contrast-media-induced nephrotoxicity are disturbances of renal microcirculation due to prolonged intrarenal vasoconstriction, and direct damaging effects on glomerular and tubular cells. Calcium channel blocking agents have been shown experimentally and clinically to ameliorate ischaemic and toxic renal injury. In the present prospectively randomised, double-blind clinical trial, we investigated a total of 35 patients after intravascular administration of contrast media to determine the effects on renal function of a 3-day treatment with the calcium channel blocker nitrendipine (20 mg/day orally, starting 1 day before X-ray examination, n = 16), compared to findings in a placebo-treated control group (n = 19). Despite the fact that baseline renal function was significantly more compromised in the investigational group, the prophylactic application of nitrendipine preserved the glomerular filtration rate, whereas control patients showed a significant (27%) reduction in GFR on day 2 after contrast-media injection (P less than or equal to 0.01). Moreover, the increase in enzymuria of three different renal enzymes (gamma-GT, AAP, and beta-NAG), as well as urinary protein excretion, was significantly ameliorated by nitrendipine. These data confirm previous findings of our group in patients after kidney transplantation, indicating that prophylactic and/or therapeutic application of calcium channel blockers is of substantial value in preventing ischaemic or toxic renal injury.(ABSTRACT TRUNCATED AT 250 WORDS)

Contrast Media↗

PubMed1989

Renal and hepatic tolerance of nonionic and ionic contrast media in intravenous digital subtraction angiography.

The liver and kidney tolerance of iopromide 370 in comparison to that of sodium meglumine diatrizoate 370 or iopamidol 370 in doses of 2 ml/kg body weight was examined in two controlled double-blind studies with intravenous digital subtraction angiography on the basis of enzyme assays in serum and urine. In patients with normal kidney function no changes were observed in the levels of the liver enzymes GPT, GOT, and gamma glutamyl transpeptidase (GGT) serum up to 72 hours after injection of iopromide or sodium meglumine diatrizoate. Among the kidney-specific enzymes, the excretion of GGT in urine increased after injection of iopromide and iopamidol. The maximum increase of GGT excretion was, however, statistically significantly lower in the group treated with iopromide than in the iopamidol group. Within 72 hours, the activities had been returned to the initial values in both groups.

Angiography↗

PubMed1988

Delta subunit of chloroplast coupling factor 1 inhibits proton leakage through coupling factor O.

The ATP synthase of chloroplasts consists of a proton-conducting portion, CF0, and a catalytic portion, CF1. The smaller subunits of CF1, in particular delta, may play a key role in the coupling of proton transport to ATP synthesis. Purified subunit delta, when added to partially CF1-depleted thylakoid membranes, can restore photophosphorylation (Engelbrecht, S., and Junge, W. (1987) Eur. J. Biochem. 172, 213-218). We report here that it does so by blocking proton conduction through CF0. Thylakoids were CF1-depleted by incubation in hypoosmolar NaCl/EDTA solutions. Variation of the NaCl concentrations and of the incubation times not only changed the overall degree of CF1 depletion but also the subunit composition of solubilized CF1, namely CF1 containing delta and CF1(-delta). This was quantified by immunoelectrophoresis and by fast protein liquid chromatography. Proton conduction was measured by flash spectrophotometry by using standard electrochromic and pH-indicating absorption changes. The removal of integral CF1 was correlated with high electric conductance of thylakoid membranes, an increased extent of rapid proton leakage, and loss of ATP synthesis activity, which exceeded the percentual loss of CF1. The removal of predominantly CF1(-delta) resulted in comparatively lesser effects on the loss of ATP synthesis and on the extent and velocity of proton leakage. On the same line, addition of integral CF1 and of purified delta diminished the electric leak in CF1-depleted thylakoids. Both approaches, the controlled removal of CF1 and CF1(-delta), respectively, and addition of delta and CF1 showed that delta can act as a "stopcock" to the exposed proton channel CF0.

Adenosine Triphosphate↗

PubMed1988

Purified subunit delta of chloroplast coupling factor CF1 reconstitutes photophosphorylation in partially CF1-depleted membranes.

The ATP synthase of chloroplasts consists of the proton channel, CF0, and the catalytic part, CF1, which carries nucleotide-binding sites on subunits alpha and beta. The still poorly understood interaction between CF0 and the catalytic sites on CF1 is mediated by the smaller subunits gamma, delta and epsilon of CF1. We investigated the ability of purified delta to block proton leakage through CF0 channels after their exposure by removal of the CF1 counterpart. Thylakoids were partially depleted of CF1 by EDTA treatment. This increased their proton permeability and thereby reduced the rate of photophosphorylation. Subunit delta was isolated and purified by FPLC [Engelbrecht, S. and Junge, W. (1987) FEBS Lett. 219, 321-325]. Addition of delta to EDTA-treated thylakoids reconstituted high rates of phenazine-methosulfate-mediated photophosphorylation. Since delta does not interact with nucleotides by itself, the reconstitution was due to a reduction of the proton leakage through open CF0 channels. The molar ratio of purified delta over exposed CF0, which started to elicit this effect, was 3:1. However, if delta was added together with purified CF1 lacking delta, in a 1:1 molar ratio, the relative amount over exposed CF0 was as low as 0.06. This corroborated our previous conclusion [Lill, H., Engelbrecht, S., Schönknecht, G. and Junge, W. (1986) Eur. J. Biochem. 160, 627-634] that only a very small fraction of exposed CF0 was actually proton-conducting but with a very high unit conductance. CF1 including delta was apparently rebound preferentially to open CF0 channels. Although the ability of delta to control proton conduction through CF0 was evident, it remains to be established whether delta acts as a gated proton valve or as a conformational transducer in the integral CF0CF1 ATPase.

Adenosine Triphosphate↗

PubMed1988

The photosynthetic water oxidase: its proton pumping activity is short-circuited within the protein by DCCD.

The photosynthetic water oxidase is composed of 15 polypeptides which are grouped around two functional parts: photosystem II and the catalytic manganese centre. Photochemically driven vectorial electron transfer between the manganese centre and bound plastoquinone causes deprotonation-protonation reactions at opposite sides of the thylakoid membrane. Thereby the water oxidase acts as a proton pump. Incubation of stacked thylakoids with N,N'-dicyclohexylcarbodiimide (DCCD) short-circuited its proton pumping activity. Under flashing light, the extent of both proton release into the lumen by water oxidation and of proton uptake from the medium by reduced quinone was diminished. Instead there was a rapid electrogenic backreaction with a strong H/D-isotope effect. Apparently protons which were produced by water oxidation were channelled across the transmembrane protein to the bound quinone. A more rapid protonation of the reduced quinone was evident from a shortening of the time lag for the reduction of photosystem I. These effects were paralleled by the preferential labelling with [C]DCCD in stacked thylakoids of two polypeptides with 20 and 24 kd apparent molecular mass. These may be capping the oxidizing and the reducing terminus of the water oxidase to control proton extrusion and proton uptake respectively.

Journal Article↗

PubMed1988

[Estimate of digestibility in dairy cows using an indicator method in comparison to the Hohenheimer feed value test].

In order to measure the digestibility of feed with an indicator method two trials were realized on the dairy research farm "Karkendamm". The first trial was to test the suitability of TiO2 as an indicator to determine the digestibility in cows. The rate of recovery of the indicator was 98.8% (95.5%-101.9%). The concentration of TiO2 of the rectal samples in the morning (daily or every second day) corresponded very well with the values from total faeces collection. The samples taken in the evening showed lower concentrations. The estimation of digestibility of organic matter led to the same values with the total collection or the indicator method with morning samples. The digestibility derived from evening samples were 1.7-2.3%-units digestibility derived from evening samples were 1.7-2.3%-units lower in comparison to total collection. In the second trial the digestibility derived from the in vitro method "Hohenheimer-Futterwert-Test" and from a digestion trial with 30 cows using the indicator method were compared. The digestibility calculated from the date of the in vivo trial was 9.9%-units lower than the one from the "Hohenheimer-Futterwert-Test". The depression of digestibility was due to the variation in concentrate feeding between cows. If the cows got less than 8 kg concentrates the depression in digestibility was 1.9% when increasing the level of feeding one unit of maintenance requirement. If the cows got more than 8 kg concentrates the depression was 3.1%-units. It could be concluded that the "Hohenheimer-Futterwert-Test" underestimates the digestibility if the level of feeding is increased to a certain extent.

Animal Feed↗