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J Voigt

Publications and source records attributed to J Voigt.

At least 19 recordsLinked to original sources
PubMed2005

[Contents of the glucose transporters GLUT1 and GLUT4 in oxidative and glycolytic muscles of goat kids and adult goats].

The objective of this study was to elucidate, whether the impaired insulin sensitivity with regard to glucose utilisation in ruminating goats compared with suckling goat kids may be due to a reduced expression of the glucose transporters GLUT1 and GLUT4 in skeletal muscle. Muscle samples were removed from red, oxidative muscles (M. masseter, diaphragm) and white, glycolytic muscles (M. longissimus dorsi, and M. semitendinosus) of five goat kids fed with milk exchanger and nine adult goats of different stages of life. Samples were analysed for their GLUT1 and GLUT4 contents. The muscles were characterised metabolically by measuring the activities of isocitrate dehydrogenase (ICDH) and of lactate dehydrogenase. In all four analysed muscles the GLUT4 contents of adult goats were significantly (p < 0.05) lower than in goat kids. Significant differences concerning the GLUT4 contents in skeletal muscles were not detected in adult goats of different stages of life. The GLUT1 contents differed to a lower extend between goat kids and adult goats. The results of this investigation indicate that the impaired insulin sensitivity of adult compared with suckling ruminants is accompanied by or leads to a decreased GLUT4 expression.

Aging↗
PubMed2005

[Utilization of glucose and long-chain fatty acids in lactating dairy cows fed a fat-enriched diet].

The fate of carbon from long-chain fatty acids and glucose in dairy cows which were fed with protected fat was studied using stable isotope technique. The experiment was carried out on two groups of dairy cows (n=16 in each group) during the first 15 weeks of the lactation period. The cows were fed isoenergetic and isoproteinogenous diets based on corn silage. About 1.8 kg of tapioca starch in the diet of the starch group was substituted by about 0.7 kg of rumen protected fat (Ca salts of palm oil and soybean oil) in the diet of the fat group. The carbon atoms of dietary fat were naturally depleted in 13C as compared to carbon atoms of starch. Daily milk performance and lactose output were significantly (P < 0.05) higher among the cows fed with fat diet. In comparison to the starch group, the enrichment of milk fat with 13C was significantly lower, while that of breath CO2 was significantly higher in the fat group (P < 0.05). This means the fatty acids were incorporated into milk fat in preference to metabolic oxidation. Further studies showed that blood glucose is oxidized to a lower extent and is used for the synthesis of lactose to a higher proportion if the cows were fed with the fat diet. The glucose entry rate into the body glucose pool was not different between the diets. In conclusion, the dietary fatty acids perform a glucose sparing effect and improve the glucose supply for the mammary gland.

Animal Feed↗
PubMed2004

Ruminal degradability of 15N labelled ribonucleic acid in grass.

The ruminal degradation of RNA in rye grass (Lolium perenne) was studied using the bag method. A non-lactating cow (BW 550 kg) fitted with a rumen cannula was used and fed twice daily at maintenance level with a chopped grass hay-based ration containing 30% ground barley. Rye grass, labelled during growth by fertilization with 15N2-urea (9.5 atom% 15N, 20 g N/m2), was cut at seven stages of growth and maturity and freeze-dried. RNA-N represented 6 to 17% of total N. Labelled grass samples (milled to 5.0 mm screen, 5.0+/-0.1 g DM) were incubated in polyester bags (100 x 200 mm, pore size 50 microm) in the rumen for periods of 1, 3, 6, 9, 12, 24, and 48 h. Data of N and RNA disappearances from the bags were fitted to an exponential equation to estimate parameters of degradation. The effective degradability of RNA in the rumen averaged 90+/-4%, for N it was 11% units lower (P < 0.001). Degradability of RNA was correlated to that of N (R2 = 0.92). Degradability of RNA (R2 = 0.96) and N (R2 = 0.93) decreased with increasing fibre content of grass. Increasing the fibre content by 1% diminished the degradability of RNA and N by 1.1% units and 2.4% units, respectively (P < 0.001). Assuming a microbial protein synthesis in the rumen of 150 g/kg DOM, a N: RNA ratio of 1:1.35 in rumen microbes and a rumen outflow rate of 0.06 h(-1), a model calculation indicates that about 9 to 19% of duodenal RNA are of dietary origin in animals fed grass. This should be taken into account for the calculation of microbial N on the basis of RNA as marker.

Animals↗
PubMed2003

Effects of protozoa on methane production in rumen and hindgut of calves around time of weaning.

Effects of the presence or absence of ciliate protozoa on methanogenesis in the rumen and hindgut were investigated in young calves during a 7-week period. Ten Holstein calves, aged 7 days, were divided in two groups (n = 5) and fed an increasing amount of a commercial milk replacer and small amounts of a calves starter. One group was inoculated with ciliate fauna on two occasions, week 5 and 6, while the second remained ciliate-free. The absence of protozoa in the rumen decreased rumen empty weight (-23%, P < 0.01), and rumen pool size of N (-36%, P < 0.01) and crude fat (-37%, P < 0.05). Rumen bacteria of non-faunated calves contained a higher proportion of total amino acid-N per 16 g N (+3%, P < 0.01) and D-alanine-N per 16 g N (+13%, P < 0.05) compared to faunated calves. Further results contain a reference for a higher bacterial mass in the ciliate-free rumen with an increased number of bacteria adherent to rumen mucosa. The CH4 production in the rumen increased exponentially with the increase in protozoa population size (R2 = 0.68). In presence of 46 x 10(4) protozoa per ml rumen fluid, the in vitro CH4 production of rumen fluid per mol total VFA was about 34% higher in faunated than in non-faunated calves (P < 0.001). Hydrogen (2H) recovery of rumen fermentation was positively correlated (R2 = 0.55) to the CH4 production rate. Methanogens were attached on rumen mucosa. Methanogenesis, induced by rumen mucosa attached bacteria, was stimulated by ruminal protozoa. In the absence of protozoa in the rumen, the acetate-propionate ratio and butyrate proportion of VFA were reduced. In vivo, in the absence of protozoa not only the whole animal CH4 production (-30%, P < 0.05) but also the digestibility of carbohydrates (-4%, P < 0.05) was reduced. Thereby no difference was observed in the intake of ME per kg DM between the groups. In conclusion, the methanogenesis in the rumen, but not in hindgut, is associated with the development of the ruminal protozoa population. The level of methanogenesis (mol/mol VFA) in the hindgut amounts to 20% of the ruminal methanogenesis.

Ammonia↗
PubMed2003

Influence of nutrition level on digestibility in high yielding cows and effects on energy evaluation systems.

The objective of the study was to determine the effect of nutrition level (NL, multiples of maintenance energy requirement) on the digestibility of nutrients for dairy cows regarding the energy supply of the animal. The digestion of nutrients and energy was investigated in two trials using lactating dairy cows. The NL varied from 2.7 to 5.0 using diets similar composition. In addition, sheep were given the same feed with a NL of 1.4. Digestibility of dry matter (DM) and all specific measures of dietary components declined significantly as NL increased. Digestibility of energy decreased by 4.1% for each increase in NL. The metabolizable energy, the ability to metabolize energy (metabolizable energy/gross energy), and the content of net energy for lactation (NE(L)) per kilogram of DM intake were calculated for NL from 1 to 6 on the basis of these relationships and as well as the gross energy, methane energy, and urine energy. Accordingly the NEL content declined by 0.11 MJ/kg of DM intake or 1.6% as the NL increased by one unit. It means that the NE(L) requirement above the maintenance requirement increased by 0.07 MJ of NE(L) per kilogram of fat-corrected milk, if the NL increased by one unit.

Animal Nutritional Physiological Phenomena↗
PubMed2002

Research note: Postnatal development of electrolyte transport in calf rumen as affected by weaning time.

In a previous study we found a positive correlation between early weaning in calves and morphological parameters which were indicative of ruminal development, i.e. the length and width of the papillae. The objective of the present study was to determine to what extent this observation could be reflected by modulations of absorptive and secretory functions of the rumen mucosa. For this purpose the short-circuit currents (Isc) as a measure of electrogenic net ion fluxes and the transepithelial conductances (G(T)) as a measure of the overall tissue permeability were measured in vitro applying the Ussing-chamber technique. Simultaneously, the unidirectional flux rates of sodium and chloride across rumen wall epithelia were determined in the absence of electrochemical gradients. Under these conditions, significant positive net flux rates (Jnet) clearly indicate active mechanisms for electrolyte absorption. For the experiments 12 male Holstein calves 7 d of age were assigned to three groups of 4 animals each: milk group (I, slaughtered after 6 weeks of age), late weaning group (II, slaughtered after 9 weeks of age) and early weaning group (II, weaned after 6 weeks of age and slaughtered after 9 weeks of age). Whereas G(T) values remained unaffected by different age and feeding, Isc values were significantly affected by early weaning but were not influenced by age. Irrespective of weaning time active absorption of Na+ tended to be higher by about 60% in 9 weeks old animals. Active absorption of chloride was significantly increased in milk fed 9 weeke old calves and this effect was further stimulated by early weaning. In conclusion, the data show an increasing active Na+ absorption with age in calf rumen that could not be influenced by early weaning. Similarly, active Cl- absorption was initially increased during postnatal development and this effect could be stimulated further by early weaning.

Absorption↗
PubMed2001

Utilization of a peptide lead for the discovery of a novel PTP1B-binding motif.

Examination of the PTP1B inhibitory potency of an extensive series of phosphotyrosyl (pTyr) mimetics (Xxx) expressed in the EGFr-derived hexapeptide platform Ac-Asp-Ala-Asp-Xxx-Leu-amide previously led to the finding of high inhibitory potency when Xxx = 4-(phosphonodifluoromethyl)phenylalanyl (F2Pmp) (K(i) = 0.2 microM) and when Xxx = 3-carboxy-4-carboxymethyloxyphenylalanyl (K(i) = 3.6 microM). In the first instance, further work led from the F2Pmp-containing peptide to monomeric inhibitor, 6-(phosphonodifluoromethyl)-2-naphthoic acid (K(i) = 22 microM), and to the pseudo-dipeptide mimetic, N-[6-(phosphonodifluoromethyl)-2-naphthoyl]-glutamic acid (K(i) = 12 microM). In the current study, a similar approach was applied to the 3-carboxy-4-carboxymethyloxyphenylalanyl-containing peptide, which led to the preparation of monomeric 5-carboxy-6-carboxymethyloxy-2-naphthoic acid (K(i) = 900 microM). However, contrary to expectations based on the aforementioned F2Pmp work, incorporation of this putative pTyr mimetic into the pseudo-dipeptide, N-[5-carboxy-6-carboxymethyloxy-2-naphthoyl]-glutamic acid, resulted in a substantial loss of binding affinity. A reevaluation of binding orientation for 5-carboxy-6-carboxymethyloxy-2-naphthoic acid was therefore undertaken, which indicated a 180 degrees reversal of the binding orientation within the PTP1B catalytic site. In the new orientation, the naphthyl 2-carboxyl group, and not the o-carboxy carboxymethyloxy groups, mimics a phosphoryl group. Indeed, when 5-carboxy-2-naphthoic acid itself was examined at neutral pH for inhibitory potency, it was found to have K(i) = 31 +/- 7 microM, which is lower than parent 5-carboxy-6-carboxymethyloxy-2-naphthoic acid. In this fashion, 5-carboxy-2-naphthoic acid (or more appropriately, 6-carboxy-1-naphthoic acid) has been identified as a novel PTP1B binding motif.

Catalytic Domain↗
PubMed2001

Macrocyclization in the design of a conformationally constrained Grb2 SH2 domain inhibitor.

Grubbs' olefin metathesis reaction was utilized to prepare a macrocyclic variant of a linear Grb2 SH2 domain antagonist in an attempt to induce a beta-bend conformation known to be required for high affinity binding. In extracellular Grb2 SH2 domain binding assays, the macrocyclic analogue exhibited an approximate 100-fold enhancement in binding potency relative to its linear counterpart. The macrocycle was not as effective in whole cell binding assays as would be expected based on its extracellular binding potency.

Adaptor Proteins, Signal Transducing↗
PubMed2001

Phosphoryltyrosyl mimetics in the design of peptide-based signal transduction inhibitors.

The central roles played by protein-tyrosine kinase (PTK)-dependent signal transduction in normal cellular regulation and homeostasis have made inappropriate or aberrant functions of certain of these pathways contributing factors to a variety of diseases, including several cancers. For this reason, development of PTK signaling inhibitors has evolved into an important approach toward new therapeutics. Since in these pathways phosphotyrosyl (pTyr) residues provide unique and defining functions either by their creation under the catalysis of PTKs, their recognition and binding by protein modules such as SH2 and phosphotyrosyl binding (PTB) domains, or their destruction by protein-tyrosine phosphatases, pTyr mimetics provide useful general starting points for inhibitor design. Important considerations in the development of such pTyr mimetics include enzymatic stability (particularly toward PTPs), high affinity recognition by target pTyr binding proteins, and good cellular bioavailability. Although small molecule, nonpeptide inhibitors may be ultimate objectives of inhibitor development, peptides frequently serve as display platforms for pTyr mimetics, which afford useful and conceptually straightforward starting points in the development process. Reported herein is a limited overview of pTyr mimetic development as it relates to peptide-based agents. Of particular interest are recent findings that highlight potential limitations of peptides as display platforms for the identification of small molecule leads. One conclusion that results from this work is that while peptide-based approaches toward small molecule inhibitor design are often intellectually satisfying from a structure-based perspective, extrapolation of negative findings to small molecule, nonpeptide contexts should be undertaken with extreme caution.

Binding Sites↗
PubMed2001

Subcellular distribution of 14-3-3 proteins in the unicellular green alga Chlamydomonas reinhardtii.

A polyclonal antibody was raised against a recombinant Chlamydomonas 14-3-3-beta-galactosidase (beta-Gal) fusion protein and characterized for its epitope specificity towards the corresponding Chlamydomonas 14-3-3 protein by scan-peptide analysis. This antibody recognized four Chlamydomonas polypeptides with apparent molecular masses 32, 30, 27, and 24 kDa, which also reacted with the antiserum depleted of anti-(Escherichia coli beta-Gal) IgG, but not with the corresponding preimmune serum or the antiserum preincubated with purified 14-3-3 proteins. Western-blot analyses performed with the antibody depleted of anti-(beta-Gal) IgG revealed that more or less pronounced levels of 14-3-3 proteins were present in all subcellular fractions of Chlamydomonas reinhardtii except the nuclei. The highest levels of 14-3-3 protein were observed in the cytosol and microsomal fraction. The 30-kDa isoform was predominant in the cytosol, whereas the 27-kDa isoform was prevalent in the microsomes. When microsomal membranes were separated by sucrose-density-gradient centrifugation, Western-blot analysis revealed distinct patterns of 14-3-3 isoforms in the endoplasmic reticulum, dictyosome, and plasma membrane fractions identified by marker enzyme activities. These findings indicate that the four 14-3-3 proteins of C. reinhardtii differentially interact with endoplasmic reticulum, dictyosomes, and plasma membrane.

14-3-3 Proteins↗
PubMed2000

Nucleotide sequence, genomic organization and cell-cycle-dependent expression of a Chlamydomonas 14-3-3 gene.

Members of the 14-3-3 protein family have been identified as regulatory elements in intracellular signalling pathways and cell cycle control. Previously we reported the nucleotide sequence of a 14-3-3 cDNA cloned from the unicellular green alga Chlamydomonas reinhardtii. In this communication, we describe the nucleotide sequence, the genomic organization and the cell-cycle-dependent expression of the corresponding gene. The coding sequence of this gene was found to be interrupted by four introns of 124, 116, 81, and 659 bp, respectively. Introns 2-4 were found in conserved positions as compared to the Arabidopsis 14-3-3 genes. A counterpart to intron 1 absent in the Arabidopsis 14-3-3 genes was found in the human 14-3-3 epsilon gene.

14-3-3 Proteins↗
PubMed2000

Resonant Coherent Anti-Stokes Raman Scattering Applied to Vapor Phase InI.

The metal halide indium iodide (InI) is used as an important additive to mercury discharge lamps. The aim of this paper is to prepare resonant coherent anti-Stokes Raman scattering (RECARS) experiments for measuring concentration and temperature profiles of InI in commercially available metal halide lamps. The spectral positions of possible RECARS lines of InI (double and triple resonances) are calculated up to rotational quantum number J = 280 and vibrational quantum number v = 10. There is evidence for triple resonances leading to strong RECARS signals at J = 174 and J = 231. Dipole transition moments are calculated, which are important input data for the determination of the RECARS spectra. A degenerate-folded BOXCARS setup with a frequency-tripled Nd:YAG laser at 355 nm pumping two dye-laser systems oscillating near 411 nm is utilized to detect RECARS signals of the rovibronic transitions between X:(1)Sigma(+) and A:(3)Pi(0)(0(+)) states of InI. The laser output is attenuated to prevent saturation of the spectra. The tunable dye-laser systems have good beam-pointing stability and a small spectral width (<0.07 cm(-1)). Measured RECARS spectra from a pure InI vapor quartz cell at p = 120 Pa and T = 880 K are compared with theoretical data and good agreement is obtained with respect to the spectral position and RECARS intensity. The scatter signals are achieved with laser-pulse energies of less than 1 µJ. A collision-constant Gamma = 0.0025 cm(-1) describes the line broadening best. The experiments are also performed at a partial InI pressure of 1.12 kPa, a partial Hg pressure of 112 kPa, and a temperature of T = 1073 K and could be interpreted with a broadening constant Gamma = 0.23 cm(-1). Temperature measurements were performed between 900 and 1200 K with an accuracy of 7%. Copyright 2000 Academic Press.

Journal Article↗
PubMed2000

[Pancreatic carcinoma].

Explore the source record for details and available documents.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2000

Occurrence of 12-methyltridecanal in microorganisms and physiological samples isolated from beef.

12-Methyltridecanal (MT) smelling tallowy, beef-like was formed from plasmalogens when beef was boiled. To clarify the origin of MT, its concentration was determined by a stable isotope dilution assay in bacteria and protozoa isolated from the rumen of bovine animals as well as in the plasma, erythrocytes, and other physiological samples. The highest amounts of MT were found in bacteria followed by protozoa. The MT content of the erythrocytes was small. The results support the hypothesis that microorganisms are the main source of MT of which a small amount is resorbed by the animal and transported to the muscular tissue where MT is incorporated into plasmalogens.

Abomasum↗
PubMed2000

Highly potent inhibitors of human cathepsin L identified by screening combinatorial pentapeptide amide collections.

By screening a combinatorial pentapeptide amide collection in an inhibition assay, we systematically evaluated the potential of 19 proteinogenic amino acids and seven nonproteinogenic amino acids to serve as building blocks for inhibitors of human cathepsin L. Particularly efficient were aromatic, bulky, hydrophobic amino-acid residues, especially leucine, and positively charged residues, especially arginine. Building blocks for potential inhibitory peptides were combined by random selection from their activity pattern. This random approach for the design of inhibitors was introduced to compensate for the inaccuracy induced by shifted docking of combinatorial compound collections at the active center of cathepsin L. Thereby, we obtained structurally defined pentapeptide amides which inhibited human cathepsin L at nanomolar concentrations. Among the most potent novel inhibitors, one peptide, RKLLW-NH2, shares the amphiphilic character of the nonamer fragment VMNGLQNRK of the autoinhibitory, substrate-like, but reverse-binding prosegment of human cathepsin L which blocks the active center of the enzyme. Obviously, RKLLW-NH2 carries the functions that are important for enzyme-peptide interaction in a condensed form. This hypothesis was confirmed by structure-activity studies using truncated and modified pentapeptides.

Amides↗
PubMed2000

Investigations on the influence of duodenal histidine infusion on nitrogen and amino acid turnover of growing German Holstein bulls.

The effect of a continuous duodenal infusion of L-histidine (His) (8 g/d) on the retention of nitrogen was investigated in two experiments (I, II), each of which was carried out using two young bulls. In Exps. I and II, the animals (150-250 kg BW) were fitted with a re-entrant cannula in the proximal duodenum and were fed diets containing 125 g CP/kg DM and 11.5 MJ ME/kg DM. A third experiment (III) using two young bulls (140-200 kg BW) fitted with a simple T-cannula was carried out infusing 6 g L-His. The animals were fed a low protein diet (94 g CP/kg DM and 11 MJ ME/kg DM). The study was done to find out whether or not L-His is the first limiting amino acid (AA) for growing ruminants. N retention was 28 and 31, 38 and 38, 22 and 24 g/d without L-His infusion and with L-His infusion for Exps. I, II and III, respectively. Both in the experiments with a standard protein supply (I, II) and in the experiment with reduced protein supply (III), no significant differences were found between periods with and without infusion of L-His. The utilisation of duodenal NAN varied between 39% and 50% and was also not significantly influenced by the duodenal infusion of L-His. No significant effect was observed on the flow of AA into the duodenum. The faecal excretion of AA was also not significantly influenced by the infusion of L-His. The utilisation of individual amino acids as calculated by the ratio of retained AA to intestinal apparently digested AA, did not differ significantly following the duodenal infusion of L-His. As expected, the utilisation of His decreased. Of the different essential AA, L-His was the most utilised (80%) followed by Arg (72%), Met (60%), Leu (45%) and Lys (44%), during periods without supplementation of L-His. It is concluded that the intestinal supply of L-His from the basal diet was sufficient for the potential growth level of animals under these experimental conditions. In all AA present at the proximal duodenum, L-His could have at first a limiting effect on the performance of growing young bulls with high body gain. Arg and Met, but not Lys, could be second or co-limiting AA.

Amino Acids↗
PubMed2000

Assignment of the lowest Qy-state and spectral dynamics of the CP29 chlorophyll a/b antenna complex of green plants: a hole-burning study.

Low-temperature absorption, fluorescence and persistent non-photochemical hole-burned spectra are reported for the CP29 chlorophyll (Chl) a/b antenna complex of photosystem II of green plants. The absorption-origin band of the lowest Qy-state lies at 678.2 nm and carries a width of approximately 130 cm-1 that is dominated by inhomogeneous broadening at low temperatures. Its absorption intensity is equivalent to that of one of the six Chl a molecules of CP29. The absence of a significant satellite hole structure produced by hole burning, within the absorption band of the lowest state, indicates that the associated Chl a molecule is weakly coupled to the other Chl and, therefore, that the lowest-energy state is highly localized on a single Chl a molecule. The electron-phonon coupling of the 678.2 nm state is weak with a Huang-Rhys factor S of 0.5 and a peak phonon frequency (omega m) of approximately 20 cm-1. These values give a Stokes shift (2S omega m) in good agreement with the measured positions of the absorption band at 678.2 nm and a fluorescence-origin band at 679.1 nm. Zero-phonon holes associated with the lowest state have a width of approximately 0.05 cm-1 at 4.2 K, corresponding to a total effective dephasing time of approximately 400 ps. The temperature dependence of the zero-phonon holewidth indicates that this time constant is dominated at temperatures below 8 K by pure dephasing/spectral diffusion due to coupling of the optical transition to the glass-like two-level systems of the protein. Zero-phonon hole-widths obtained for the Chl b bands at 638.5 and 650.0 nm, at 4.2 K, lead to lower limits of 900 +/- 150 fs and 4.2 +/- 0.3 ps, respectively, for the Chl b-->Chl a energy-transfer times. Downward energy transfer from the Chl a state(s) at 665.0 nm occurs in 5.3 +/- 0.6 ps at 4.2 K.

Light-Harvesting Protein Complexes↗