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R Lippoldt

Publications and source records attributed to R Lippoldt.

6 recordsLinked to original sources
PubMed1997

Active repression by thyroid hormone receptor splicing variant alpha2 requires specific regulatory elements in the context of native triiodothyronine-regulated gene promoters.

Structural requirements for the inhibitory action of thyroid hormone receptor splicing variant alpha2 (TR alpha2) on T3/TRbeta1-mediated transactivation were investigated in native promoters of two T3-regulated genes: the brain-specific myelin basic protein (MBP) and the housekeeping malic enzyme (ME). T3/TRbeta1 transactivation of MBP256-chloramphenicol acetyl transferase (CAT) and ME315-CAT constructs was inhibited and unaffected by TR alpha2, respectively. In electrophoretic mobility shift assays, TR alpha2 bound MBP-thyroid response element (TRE) as a monomer but failed to interact with ME-TRE. Mutations of ME-TRE allowed TR alpha2 binding but not inhibition of T3/TRbeta1-mediated transactivation. In the context of the MBP promoter, replacement of MBP-TRE with ME-TRE or exchange of MBP TATA-like box with the ME GC-rich region spanning the transcription start site abolished TR alpha2 dominant negative action. Simultaneous introduction of both MBP-TRE and MBP TATA-like box in the context of ME promoter, however, triggered TR alpha2 inhibition of T3/TRbeta1 transactivation, indicating that these regulatory elements are necessary, but not individually sufficient, to mediate TR alpha2 dominant negative activity. Functional studies at low TR alpha2/TRbeta1 ratios revealed that binding to TRE facilitates TR alpha2 dominant negative action while prevention of DNA interaction by altering TR alpha2 P-box structure preserved TR alpha2 inhibitory effect, although with lower potency. In conclusion, the results suggest that, in native promoters of T3-regulated genes, a dual molecular mechanism, with DNA-binding dependent and DNA-binding independent components, underlies TR alpha2 dominant negative activity.

Animals↗
PubMed1996

Differential 9-cis-retinoic acid-dependent transcriptional activation by murine retinoid X receptor alpha (RXR alpha) and RXR beta. Role of cell type and RXR domains.

The 9-cis-retinoic acid (9cRA)-inducible enhancer of the rat cellular retinol-binding protein type II gene (CRBP II) was shown to be differentially regulated by the murine retinoid X receptor alpha (RXR alpha) as compared with RXR beta. Transient transfection assays performed in NIH 3T3 fibroblast cells demonstrated that RXR alpha yielded a high level of 9cRA-dependent transcription of a reporter gene linked to the CRBP II enhancer, when compared with RXR beta. This effect was cell type-dependent, since both receptors elicited comparable transcriptional activation of the same reporter in P19 embryonal carcinoma cells. To further explore the structural determinants responsible for the differences between these two receptors, a series of chimeric receptor constructs were made. Co-transfection assays utilizing these chimeras demonstrated that both the N terminus and the hinge region connecting the DNA binding domain with the ligand binding domain of RXR alpha were responsible for the high level of 9cRA-dependent transcription observed in NIH 3T3 cells, Furthermore, the hinge region of RXR alpha was shown to be necessary to repress, in the absence of hormone, the transcriptional activation function located in the N-terminal domain of RXR alpha. These results stress the importance of functional links between different RXR domains and suggest an RXR subtype and cell type-dependent specificity in the control of the 9cRA response.

3T3 Cells↗
PubMed1983

[Enteral-parenteral feeding with high protein content in++ severe cranio-cerebral injuries].

Brain injured patients (BIP) usually have hugh losses of nitrogen in the early posttraumatic period. Investigations on protein catabolism in 10 young male BIP, not being moribund, were performed to answer the question whether N-loss can be minimized by an enteral-parenteral nutrition with high protein content (greater than 2 g protein/kg body weight). N-balance, 24-h urinary excretion of creatinin and 3-methylhistidine were measured for 8 days after the accident. The alimentary regime, being adapted to body weight, included for an adult 70-kg patient the intake of 470 g carbohydrates, 170 g aminoacids/proteins and 45 g fats per day (3040 kcal/day = 12700 kJ/day with 112 kcal/g N = 468 kJ/g N). Laboratory data indicated a stimulated muscle turnover rate and a considerable protein catabolism. The waste of endogenous sources could therefore not be prevented by the presented combined nutritional regime.

Adolescent↗
PubMed1977

Stability and subunit structure of human alpha2-macroglobulin.

The molecular weights of alpha2-macroglobulin and its non-covalent subunits have been determined by equilibrium centrifugation. The secondary structure of the native and the thermally denatured molecules has been analyzed by circular dichroic measurements. In contrast to most proteins the thermally denatured form contains a slightly more highly organized polypeptide chain than the native form. The relaxation time of the native protein, as determined by fluorescence polarization measurements, indicates that alpha2-macroglobulin is composed of domains smaller than that of the two subunits. The transitions in acid, alkali, and at high temperatures have been explored in order to establish the pH and thermal range of stability of alpha-macroglobin.

Drug Stability↗
PubMedDate not supplied

Pharmacokinetic evaluation of a new maintenance solution for severely injured patients.

Nine severely injured patients (SIP) and 9 healthy controls received 20 min iv infusions of Aminoplasmal-LS-10 (2.15 ml/kg body wt containing 0.215 g amino acids). Employing the values of the plasma amino acid (AA) concentrations 3, 7, 15, 30, 45, 70, and 150 min after the end of the infusion, we calculated the elimination half-life (t 1/2), the elimination constant (k2), the total clearance (Cltot), and the transfer of the individual AA. The AA showed t 1/2 between 6 (Glu) and 23 (Thr) min. Comparing the metabolic kinetics of healthy controls and SIP, there were no statistical differences in t 1/2 or in k2. In the SIP, nearly all plasma AA showed increased transfer and Cltot, significantly for Thr (p < 0.05), Pro, Gly, Ala, Arg (p < 0.02), Glu (p < 0.01), and Met (p < 0.005). In contrast, the Cltot for Phe and Tyr were decreased. Except for Phe, Tyr, Met (enhanced values) and Arg (no change), the fasting values of AA concentrations in the SIP were diminished compared to those in the healthy controls. Based on the measured transfer, we have developed a new maintenance solution adapted to SIP. Compared with Aminoplasmal, it is necessary to apply AA concentrations which are increased in Lys, His, Phe, Tyr, Val, Ala, and Ser, and reduced in Arg, Pro, Leu, Ile, and Gly.

Amino Acids↗