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At least 1,549 records · Page 86Linked to original sources
PubMed1983

The effects of different concentrations of glycerol and dimethylsulfoxide on the metabolic activities of kidney slices.

Kidney slices either were exposed to the cryoprotectants for 1 hr at room temperature and subsequently washed and incubated in fresh KR buffer containing only the radioactive metabolic tracers, or were immediately incubated for 2 hr at 37 degrees C in KR buffer containing the cryoprotectant and the tracers. Exposure to glycerol by incubation of kidney slices in Krebs-Ringer bicarbonate buffer containing varying concentrations of glycerol from 0 to 70% (v/v) resulted in a pronounced inhibitory effect on the protein synthesizing activity, while thymidine incorporation into DNA and the alpha-aminoisobutyric acid uptake through the cell membranes were less affected. Exposure of the tissue to buffer containing dimethylsulfoxide (Me2SO) in concentrations of 10 to 20% (v/v) resulted in a stimulatory effect on metabolism. At higher concentrations, Me2SO was toxic resulting in damaging effects on protein and DNA synthesis as well as on membrane integrity. The stimulatory effects of exposure to low concentrations of Me2SO on protein and DNA synthesis in kidney slices were concluded to be the result of an increased transport of precursors through the cell membranes.

Animals↗
PubMed1986

Centrally administered beta-endorphin produces prolonged changes in delta-opioid ligand activity in vivo.

Spontaneous reflex bladder contractions were recorded isometrically in urethane anesthetized rats. Bladder contractions were depressed by intracerebroventricular injections of the mu-opioid receptor agonist [D-Ala2,MePhe4,Gly(ol)5]enkephalin (DAGO) and the delta-agonist [2D-penicillamine,5D-penicillamine]enkephalin (DPDPE) respectively. The effect of DPDPE was selectively antagonized by ICI 174,864 (N,N-diallyl-Tyr-Aib-Aib-Phe-Leu-OH; Aib = alpha-aminoisobutyric acid). However following the administration of beta-endorphin the antagonistic action of ICI 174,864 could no longer be observed. In addition ICI 174,864 exhibited agonistic activity following beta-endorphin and the effects of DPDPE were prolonged in a dose related manner by beta-endorphin. These observations suggest that beta-endorphin may produce complex changes in central delta-opioid receptor activity.

Animals↗
PubMed1989

Modulation of mu-mediated antinociception by delta agonists in the mouse: selective potentiation of morphine and normorphine by [D-Pen2,D-Pen5]enkephalin.

The effect of the delta-selective agonist [D-Pen2,D-Pen5]enkephalin (DPDPE) on the antinociception produced by intracerebroventricular (i.c.v.) administration of the mu agonists morphine, [D-Ala2,NMePhe4,Gly-ol5]enkephalin (DAGO), [NMePhe3,D-Pro4]morphiceptin (PLO17), beta-endorphin, phenazocine, etorphine and sufentanil was studied in mice. Only the antinociceptive effects of morphine and normorphine were modulated by i.c.v. coadministration of a dose of DPDPE which did not produce any significant antinociception alone. Both the morphine and normorphine dose-response lines were displaced to the left in the presence of DPDPE. The delta-selective antagonist ICI174,864 (N,N-diallyl-Tyr-Aib-Aib-Phe-Leu-OH) (where Aib is alpha-aminoisobutyric acid) blocked the modulation of morphine antinociception by DPDPE. ICI 174,864 alone failed to produce either a significant increase or decrease of morphine, phenazocine, etorphine or beta-endorphin antinociception. The results of the present study provide support for the hypothesis that the enkephalins may function to modulate antinociception produced at the mu receptor; such modulation may come about via the existence of an opioid mu-delta receptor complex. The mu receptors existing in such a complex may be selectively activated by morphine and normorphine, but not the other mu agonists studied here. Thus, the enkephalins may function both to directly initiate, as well as to modulate, some forms of supraspinal mu receptor-mediated antinociception.

Animals↗
PubMed1985

Osmotic effects on bacterial transport and energetics.

Paracoccus denitrificans suspended in media containing 20-300 mM NaCl swelled progressively as the salt concentration was decreased. The increase in intracellular water volume was accompanied by an enhancement of respiration and a stimulation of the rates of net potassium and alpha-aminoisobutyric acid accumulation. It is postulated that influx of water and consequent lowering of intracellular solute concentration trigger transport mechanisms which are destined to restore the original ion and metabolite balance. Since a number of transport reactions operate against the electrochemical gradient of their substrates, energy utilization increases. The increased ATP usage and lowering of [ATP] stimulates the activity of the respiratory chain and increases oxygen uptake and energy production.

Adenosine Diphosphate↗
PubMed1992

Na(+)-dependent AIB transport by neuroblastoma cells.

Na(+)-dependent amino isobutyric acid transport by two neuroblastoma cell lines with and without amplification of the oncogene N-myc is studied. Surprisingly, the contribution of system A is greater in the cell line showing no N-myc amplification. Preliminary data support a role for essential tyrosine and cysteine residues in the active center of the carriers, mainly in system A.

Amino Acids↗
PubMed1995

Enhancing peptide antigenicity by helix stabilization.

The engineering of antigenic determinants on super secondary structures using de novo design approaches often involves synthesis of long peptide chains (35-80 residues long). This communication illustrates that the stabilization of secondary structure by rational design can also greatly enhance immunogenicity and antigenicity, but in much shorter peptide sequences (21 residues long). A peptide epitope the sequence of which has been derived from the C-terminus of the chicken riboflavin carrier protein (cRCP), H2N-Tyr-His-Ala-Cys-Gln-Lys-Lys-Leu-Leu- Lys-Phe-Glu-Ala-Leu-Gln-Gln-Glu-Glu-Gly-Glu-Glu-OH, has been chosen for analysis. Helical conformations were induced in the peptide in aqueous trifluoroethanol. Analogs were designed to stabilize this conformation in water by either the introduction of appropriately spaced ion pairs or the strongly helix nucleating residue alpha-aminoisobutyric acid (Aib), substituted for Ala/Gly, thus affording a comparison of the helix stabilization strategies. Circular dichroism (CD) results demonstrate that all the designed analogs are appreciably more helical than the parent peptide in 50% aqueous trifluoroethanol. Peptide antisera were raised for all analogs in rabbits. The affinities of these antisera for the native protein antigen, determined using a chaotrope disrupted binding assay, correlated very well with the helix content determined by CD.

Amino Acid Sequence↗
PubMed1992

Organic compounds in the Forest Vale, H4 ordinary chondrite.

We have analyzed the H4 ordinary chondrite Forest Vale for polycyclic aromatic hydrocarbons (PAHs) using two-step laser mass spectrometry (L2MS) and for amino acids using a standard chromatographic method. Indigenous PAHs were identified in the matrices of freshly cleaved interior faces but could not be detected in pulverized silicates and chondrules. No depth dependence of the PAHs was found in a chipped interior piece. Amino acids, taken from the entire sample, consisted of protein amino acids that were nonracemic, indicating that they are terrestrial contaminants. The presence of indigenous PAHs and absence of indigenous amino acids provides support for the contention that different processes and environments contributed to the synthesis of the organic matter in the solar system.

Amino Acids↗
PubMed1995

Determination of alpha-dialkylamino acids and their enantiomers in geological samples by high-performance liquid chromatography after derivatization with a chiral adduct of o-phthaldialdehyde.

Derivatization with o-phthaldialdehyde (OPA) and the chiral thiol N-acetyl-L-cysteine (NAC) is a convenient and sensitive technique for the HPLC detection and resolution of protein amino acid enantiomers. The kinetics of the reaction of OPA-NAC with alpha-dialkylamino acids was investigated. The fluorescence yield of alpha-dialkylamino acids was only about 10% of that of protein amino acids when the derivatization was carried out at room temperature for 1-2 min, which is the procedure generally used for protein amino acid analyses. The fluorescence yield of alpha-dialkylamino acids can be enhanced by up to ten-fold when the derivatization reaction time is increased to 15 min at room temperature. The OPA-NAC technique was optimized for the detection and enantiomeric resolution of alpha-dialkylamino acids in geological samples which contain a large excess of protein amino acids. The estimated detection limit for alpha-dialkylamino acids is 1-2 pmol, comparable to that for protein amino acids.

Acetylcysteine↗