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PubMedDate not supplied

Hypoxanthine-guanine phosphoribosyltransferase activity of blood and muscle in Duchenne dystrophy.

Hypoxanthine-guanine phosphoribosyltransferase (HGPRT) activity was measured in red cells and in skeletal muscles of normal and Duchenne subjects. [8-14C] hypoxanthine was used as substrate, and 5-phospho-alpha-D-ribose 1-diphosphate (PRPP) was used as the ribose-5-phosphate donor. The [8-14C] inosine monophosphate (IMP) formed was separated by high-voltage electrophoresis, and radioactivity was measured by lipid scintillation counting. HGPRT activity in Duchenne and normal red-cell hemolysates was similar, but such activity was significantly higher in Duchenne than in normal muscle homogenates. Red cells of both normal and Duchenne subjects had significantly higher enzyme activity than did skeletal muscles. It is suggested that increased HGPRT activity may be involved in enhancing protein synthesis by increasing intracellular levels of purine ribonucleotides.

Adolescent↗

PubMedDate not supplied

Increased [32P]-phosphorylation of tryptic peptides of erythrocyte spectrin in Duchenne muscular dystrophy.

Increased [32P]-incorporation in tryptic peptides of the erythrocyte membrane protein spectrin Band 2 in Duchenne muscular dystrophy (DMD) was studied in a consecutive series of 10 matched DMD/control pairs. Spectrin was [32P]-phosphorylated by cyclic AMP-independent endogenous membrane protein kinase in the presence of [gamma-32P]ATP. [32P]-labeled spectrin was isolated, purified, and subjected to tryptic cleavage with excess trypsin. The resulting peptides were separated on a high-resolution 5%/15% stacking SDS--polyacrylamide gel electrophoresis system. Liquid scintillation counting was performed on sequential slices of unstained gels. A broad [32P]-labeled band containing a number of [32P]-polypeptides was found to be more highly [32P]-phosphorylated in DMD patients than in their matched controls. This band migrated with an apparent molecular mass of 4.8-5.2 kilodaltons and contained approximately 55% of total [32P] radioactivity covalently bound to spectrin peptides. These data demonstrated an increased [32P]-phosphorylation of an identifiable tryptic peptide fraction in DMD that is consistent with previous reports of increased spectrin Band 2 [32P]-phosphorylation in DMD.

Electrophoresis, Polyacrylamide Gel↗

PubMed1991

Axotomy accelerates slow component b of axonal transport.

Because the integrity of an axon depends on the supply of proteins synthesized in the cell body, we examined the effect of axotomy on the transport of structural proteins in rat motor axons, and the effect of altered transport on the rate of outgrowth after a subsequent testing axotomy. To examine the axonal transport of structural proteins, we labeled newly synthesized proteins with 35S-methionine 7 days after a "conditioning" lesion of the sciatic nerve, and removed the nerve 7-21 days later for SDS-PAGE. Tubulin, actin, calmodulin, and the 68-kD light neurofilament protein (NF-L) were identified by fluorography and removed for liquid scintillation counting. The fastest moving structural proteins were carried by slow component b (SCb) of axonal transport, which advanced 20% faster in conditioned axons: 4.2 versus 3.5 mm/day (p less than 0.01). NF-L was not accelerated, indicating that the motor for subcomponent a (SCa) of slow axonal transport was unaffected by axotomy. To measure outgrowth distances, the testing lesions was made 7 days after the conditioning lesion, and growth cones were located by the fast transport method 3 or 9 days later. The regression analysis of outgrowth distance on time showed that sprouts elongated 25% faster in conditioned axons: 4.0 versus 3.2 mm/day (p less than 0.001). These accelerated sprouts were formed too far from the spinal cord to contain SCb proteins that were synthesized after axotomy. Because the rate of outgrowth correlated closely with the rate of SCb in outgrowing sprouts (McQuarrie and Jacob, J. Comp. Neurol. 305:139-147, 1991), we conclude that SCb is accelerated throughout the length of the axon by 7 days after axotomy.

Actins↗

PubMed1982

Elastase-induced emphysema: asynchronous bronchial, alveolar and endothelial cell proliferation during the acute response to injury.

This study was undertaken to determine whether elastase injury, which results in extensive remodelling of the hamster lung to produce a panacinar type of emphysema, also induces significant lung cell damage. Anaesthetised hamsters were given a single intratracheal injection of 0.3 mg (18 units) purified elastase (Sigma Type IV) in physiologic saline and were killed 4, 6, 8, 16, 24 h, 2, 4, 8, and 16 days after exposure. DNA synthesis was assessed by autoradiography of sectioned tissue and scintillation counting of tissue blocks using injected tritiated thymidine (3HTdR). DNA, RNA and protein levels were also measured. Saline injected and unexposed animals were used as controls. Widespread mitotic activity was induced in three separate cell compartments, the peak of activity in each compartment occurring at different times. The first peak in labelling index was seen in non-ciliated, non-secretory bronchial cells at 24 h when a value of 8 per cent was reached. This was followed by mitosis in Type II alveolar cells with a labelling index of 15 per cent at 2 days and, lastly, in endothelial cells which showed an index of 9.8 per cent at 4 days. The differences between the peaks was significant (P less than 0.001). RNA content on elastase-exposed animals showed prolonged depression and had not regained control values by the end of the experiment. Protein and DNA content, and 3HTdR incorporation showed significant elevations, particularly about the fourth day after injury. Protein and DNA content and 3HTdR incorporation were not significantly changed in either group of controls.

Animals↗

PubMed2006

Prenatal diagnosis of the Cockayne syndrome: survey of 15 years experience.

OBJECTIVE: Evaluation of results in a consecutive series of 29 prenatal diagnoses for the Cockayne syndrome. METHODS: Recovery of DNA-synthesis in UV-irradiated cultured fetal cells was measured by scintillation counting of incorporated (3)H-thymidine. Semiquantitative autoradiographic assessment of the recovery of RNA-synthesis (RecRS) was used as an adjunctive method. RESULTS: In 26 of the 29 pregnancies at risk, a definite diagnosis was directly made, based on normal (n = 23) or clearly reduced (n = 3) recovery of DNA-synthesis in UV-irradiated cultured chorionic villus (CV) cells (n = 23) or amniocytes (n = 3). Adjunctive studies were performed in several pregnancies to corroborate the initial results. On three occasions initial results were unreliable, which required investigation of the recovery of RNA-synthesis (n = 2) or even additional amniocentesis (n = 1) to achieve a firm diagnosis. Thus, four affected fetuses were diagnosed in 29 pregnancies at risk (13.8%). CONCLUSION: Reliable prenatal diagnosis of the Cockayne syndrome can be made by the demonstration of a strongly reduced recovery of DNA-synthesis in UV-irradiated cultured chorionic villus cells or amniocytes. Assessment of the recovery of RNA-synthesis was needed as an adjunctive method in rare cases of poor cell growth and DNA-synthesis.

Amniotic Fluid↗

PubMed2005

A quantitative investigation into the losses of proteins at different stages of a two-dimensional gel electrophoresis procedure.

We report the results of a systematic investigation to quantify the losses of protein during a well-established two-dimensional polyacrylamide gel electrophoresis (2-DE) procedure. Radioactively labelled proteins ([(14)C]bovine serum albumin and a homogenate prepared from the liver of a rat that had been injected with [(35)S]methionine) were used, and recovery was quantified by digesting pieces of gel in H(2)O(2) and subjecting the digests to liquid scintillation counting. When samples were loaded onto the first dimension immobilised pH gradient strips by in-gel rehydration, recovery of protein from the strips was 44-80% of the amount of protein loaded, depending on the amount of protein in the sample. Most of the unrecovered protein appeared to have adhered to the reswelling tray. Losses during isoelectric focusing (IEF) were much smaller (7-14%), although approximately 2% of the protein appeared to migrate from sample strips to adjacent blank strips in the focussing apparatus. A further 17-24% of the proteins were lost into the buffers during equilibration prior to running in the second dimension. Losses during the second dimension run and subsequent staining with SYPRO Ruby amounted to less than 10%. The overall loss during 2-DE was reduced by approximately 25% when proteins were loaded onto the IEF strips using sample cups instead of by in-gel rehydration. These extensive and variable losses during the 2-DE procedure mean that spot intensities on 2-DE gels cannot be used to derive reliable, quantitative information on the amounts of proteins present in the original sample.

Animals↗

PubMed2006

A novel 14C-postlabeling assay using accelerator mass spectrometry for the detection of O6-methyldeoxy-guanosine adducts.

Accelerator mass spectrometry (AMS) is currently one of the most sensitive methods available for the trace detection of DNA adducts and is particularly valuable for measuring adducts in humans or animal models. However, the standard approach requires administration of a radiolabeled compound. As an alternative, we have developed a preliminary 14C-postlabeling assay for detection of the highly mutagenic O6-methyldeoxyguanosine (O6-MedG), by AMS. Procedures were developed for derivatising O6-MedG using unlabeled acetic anhydride. Using conventional liquid chromatography/mass spectrometry (LC/MS) analysis, the limit of detection (LOD) for the major product, triacetylated O6-MedG, was 10 fmol. On reaction of O6-MedG with 14C-acetic anhydride, using a specially designed enclosed system, the predominant product was 14C-di-acetyl O6-MedG. This change in reaction profile was due to a modification of the reaction procedure, introduced as a necessary safety precaution. The LOD for 14C-di-acetyl O6-MedG by AMS was determined as 79 amol, approximately 18,000-fold lower than that achievable by liquid scintillation counting (LSC). Although the assay has so far only been carried out with labeled standards, the degree of sensitivity obtained illustrates the potential of this assay for measuring O6-MedG levels in humans.

Acetic Anhydrides↗

PubMed1983

Comparative distribution and metabolism of triamcinolone acetonide and cortisol in the rat embryomaternal unit.

Triamcinolone acetonide (TAC) is teratogenic in rats while cortisol has been reported as not teratogenic. The objective of this investigation was to determine whether this difference in teratogenicity could be due to a difference in the metabolism and distribution of the parent compound in the embryomaternal unit. 3H-TAC and 14C-cortisol were administered intramuscularly to pregnant rats on day 12 of gestation. These dams were killed at each of the following time points after injection: 0.5, 1, 3, 6 and 24 hr. Maternal plasma and embryos were analyzed by high performance liquid chromatography (HPLC) and liquid scintillation counting. The plasma concentration of parent TAC was significantly greater than that for parent cortisol at all time points. The plasma elimination half-life for TAC, 86 min, was also calculated to be significantly longer than that for cortisol, 8 min. Furthermore, the percentage of total plasma radioactivity representing HPLC resolved TAC was much higher than that representing cortisol at all time points. The concentration of TAC in the embryos was significantly greater than for cortisol at all time points. The elimination half-life for unchanged TAC in the embryos was 142 min compared to 22 min for cortisol. The percentage of total radioactivity in the embryos representing unchanged TAC was similar to that found in maternal plasma while the percentage of total radioactivity representing unchanged cortisol was much lower than that found in maternal plasma. These findings support the hypothesis that differences in the distribution and metabolism of the parent compound are a critical factor in determining the teratogenicity of that compound.

Animals↗

PubMed1993

Proteoglycan synthesis in fetal tendon is differentially regulated by cyclic compression in vitro.

The predominant proteoglycan in tensional regions of tendon is the small proteoglycan decorin. However, a fibrocartilaginous tissue containing large amounts of aggrecan and biglycan develops at points where tendon wraps under bone and is subjected to compressive loading in addition to tension. The hypothesis that local compression regulates the development of fibrocartilage in tendon was tested by assessing the effect of in vitro compressive loading on proteoglycan synthesis. Fetal bovine deep flexor tendon explants from the region which would have become fibrocartilage were subjected to 3 days of continuous cyclic uniaxial compression (unconfined) to 30% strain, at a frequency of 1 cycle/6 s (0.17 Hz). Compression was perpendicular to the long axis of the tendon. Large proteoglycan, biglycan, and decorin were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and [35S]sulfate incorporated into each proteoglycan was quantitated by liquid scintillation counting of gel slices. The primary effect of compression was to stimulate selectively synthesis of large proteoglycan and biglycan. Incorporation of [35S]sulfate into large proteoglycan was increased 100-300% and incorporation into biglycan was increased 50-150% in compressed tissue compared to matched uncompressed tissue segments. Incorporation into decorin was unchanged. A similar effect on radio-sulfate incorporation was seen following loading of tissue from the tensional region of tendon, which does not normally develop into fibrocartilage. Proteoglycans from compressed tissue were larger, due to slightly longer glycosaminoglycan chains. Disaccharide analysis showed that the C6S/C4S ratio was higher in both the large and the small proteoglycan populations from compressed tissue. Aggrecan mRNA levels were increased approximately fivefold in loaded tissue, and SDS-PAGE analysis of [3H]leucine-labeled core proteins indicated that large proteoglycan core protein synthesis was increased by compression. The selective changes in large proteoglycan and biglycan synthesis, and in the sulfate composition and size of the glycosminoglycan chains, are consistent with what might be expected during development of fibrocartilage in vivo. These observations support the hypothesis that compressive force can regulate the development of fibrocartilaginous tissue in tendon.

Animals↗

PubMed1994

Iron mobilization from crocidolite asbestos by human lung carcinoma cells.

Neutron-activated crocidolite, containing 55Fe and 59Fe, was used to determine whether iron was mobilized from crocidolite phagocytized by cultured human lung carcinoma cells (A549 cells). Cells were treated with neutron-activated crocidolite in medium at pH 6.8 or 7.4 for 24 h. The mobilization of iron into two subcellular fractions, 10,000g supernatant (total iron) or < 10,000 MW [low-molecular-weight (LMW)] was monitored using scintillation counting. Iron was mobilized from crocidolite at a rate similar to that observed in vitro when citrate was incubated with crocidolite for 24 h at pH 7.4, but the amount mobilized was greater when cells were cultured at pH 6.8 than at 7.4. Iron mobilization was not due to the medium nor did it appear to be due to differences in the amount of crocidolite phagocytized. At the highest concentration of crocidolite used for treatment at pH 7.4 (4.5 micrograms/cm2), a total of 3600 pmol iron/10(6) cells was mobilized of which 54 pmol/10(6) cells was in a LMW fraction. After estimation of the volume of the cells, this was calculated to be equivalent to an intracellular concentration of 1.4 mM iron of which 22 microM was in the LMW fraction. Cell survival decreased linearly as the iron mobilized into the LMW fraction increased, independent of the pH of the culture medium being used. These results suggest that iron mobilization from crocidolite into a LMW fraction may represent "iron overload" in cells which have phagocytized the fibers and may be responsible for crocidolite-dependent cytotoxicity and possibly other crocidolite-dependent biological effects.

Asbestos, Crocidolite↗

PubMed1993

Protein kinase assay using tritiated peptide substrates and ferric adsorbent paper for phosphopeptide binding.

The recently described synthesis of ferric adsorbent paper has made possible the modification of protein kinase assays. The adsorbent contains ferric chelate groups, which are responsible for the binding of phosphopeptide via phosphate group. The selective adsorption of phosphopeptide contra nonphosphorylated peptide allows the use of tritium-labeled peptides and unlabeled ATP as substrates. The binding of the reaction product to the adsorbent was complete and was not affected by the amino acid sequence of the peptide. The conditions required for the separation of the produced phosphopeptide from the initial peptide have been worked out as well. The firmly bound phosphopeptide should be released from the ferric adsorbent paper prior to liquid scintillation counting. Using 0.1 m NH4HCO3 solution (pH 8.0), the elution of phosphopeptides was almost complete. The modified protein kinase assay proposed herein is rapid and allows handling of multiple samples simultaneously. In addition, the ferric paper method avoids the use of 32P-isotope, replacing it with 3H which has lower radiation energy and a much longer half-life.

Adsorption↗

PubMed1993

An assay for carbonic anhydrase activity and reactions that produce radiolabeled gases or small uncharged molecules.

An assay procedure for carbonic anhydrase activity is described. Unique to this method is the use of radiolabeled bicarbonate and a reaction vessel with a gas-permeable membrane. The method detects 14CO2 production directly and can be used at room temperature and with solutions buffered over a wide pH range. Assays are rapid (5-10 s), discounting elution and scintillation counting time. The equipment required is simple and inexpensive, marking the method ideal for routine determinations of carbonic anhydrase activity. The method can also be applied to other reactions that liberate radioactive CO2, other labeled gases, or small unchanged, labeled molecules.

Animals↗

PubMed1993

A method for the determination of UDP-glucuronosyltransferase activity toward arylcarboxylic acids.

A fast and reliable method for the assay of UDP-glucuronosyltransferase (UGT) activity toward aglycones containing a carboxylic acid function is described. The procedure involves incubation with UDP-[U-14C]-glucuronic acid, the common substrate for the reaction, solid-phase separation of the radiolabeled acylglucuronides and unreacted cofactor, and quantification by liquid scintillation counting. The technique was validated for each of the seven substrates tested by reversed-phase HPLC, and was then applied successfully to the determination of optimal conditions for the activation of the carboxylic acid-UGT, and the estimation of kinetic constants for the glucuronidation of clofibric acid, 2-naphthylacetic acid, naproxen, and 4,4,4-triphenylbutanoic acid in rat liver microsomes. From the results obtained, we believe that this is an assay which, with only minor modification, could be applied to a wide range of carboxylic acid substrates for which, until now, specific and sensitive assays have been largely unavailable.

Animals↗

PubMed1994

On the assay of acetyl-CoA synthetase activity in chloroplasts and leaf extracts.

Acetyl-CoA synthetase activity in vitro is assayed quickly and conveniently by incubating whole chloroplasts, chloroplast extracts, or leaf extracts with labeled acetate, CoA, ATP, and Mg and transferring aliquots of the reaction mixture to pieces of either Whatman No. 1 or DE81 filter paper. Unreacted acetate is quantitatively washed from the papers while the acetyl-CoA, which binds quantitatively, is determined by scintillation counting. Enzyme activity is absolutely dependent upon the presence of CoA, ATP, and Mg in reaction mixtures. The reaction has a broad pH optimum around pH 8.5. Potassium is required for maximum activity, and lithium strongly inhibits the reaction. The product retained on the papers was characterized as acetyl-CoA by several methods. On a chlorophyll basis, acetyl-CoA synthetase activities were about 25% higher in leaf homogenates than in intact chloroplasts isolated from similar leaves. Enzyme activities in the optimized assay were three- to fourfold greater than previously reported.

Acetate-CoA Ligase↗

PubMed1994

Quantification of 35S-labeled proteoglycans complexed to alcian blue by rapid filtration in multiwell plates.

This paper describes a rapid filtration assay for the quantification of 35S-labeled proteoglycans and/or 35S-labeled glycosaminoglycans in a large number of samples. Separation of 35S-labeled proteoglycans and 35S-labeled glycosaminoglycans from unincorporated [35S]sulfate is effected by forming insoluble complexes between alcian blue and the glycosaminoglycan moieties of the proteoglycans and then filtering the solutions through "Durapore membrane" discs (0.45 microns pore size) fitted in a 96-well plate. Following brief rinsing steps, the discs are punched out and 35S-labeled macromolecules retained on the membrane are then quantified by scintillation counting. In this rapid filtration assay, the relationship between the amount of [35S]-aggrecan applied and radioactivity measured was linear over a broad range of concentrations (2-800 micrograms aggrecan/ml). The amount of 35S-labeled proteoglycans measured in media and 4 M guanidine HCl extracts of articular cartilage and three different chondrocyte culture systems (monolayer, agarose gel, and alginate bead) ranged between 90 and 101% of the value obtained by sieve chromatography on Sephadex G-25. The presence in samples of unlabeled proteoglycans (up to 1 mg/ml), bovine serum albumin (up to 4 mg/ml), DNA (up to 20 micrograms/ml), serum (up to 30%), or guanidine hydrochloride at 4 M did not affect recovery of 35S-labeled proteoglycans measurably. CPM values obtained for 35S-labeled proteoglycans or 35S-labeled glycosaminoglycans quantified by chromatography on Sephadex G-25 and the filtration assay showed a strong linear relationship (r > 0.99) irrespective of the type of culture medium, extract, or digest used.

Alcian Blue↗

PubMed1994

High-pressure liquid chromatography assay for quantitatively monitoring spore photoproduct repair mediated by spore photoproduct lyase during germination of uv-irradiated Bacillus subtilis spores.

The major DNA photoproduct formed upon uv irradiation of Bacillus subtilis spores is the thymine dimer 5-thyminyl-5,6-dihydrothymine, informally referred to as spore photoproduct (SP). A rapid separation technique for detecting and quantitating SP by HPLC was developed to replace traditional paper chromatography. Tritiated thymine and thymine-containing photoproducts from trifluoroacetic acid-hydrolyzed DNA purified from uv-irradiated cells or spores of B. subtilis were identified and isolated from paper chromatograms, subjected to HPLC on a Microsorb phenyl 5-microns column using 100% water as the mobile phase, and detected by scintillation counting of collected fractions. At a flow rate of 1.8 ml per minute, thymine-containing compounds eluted in the order thymine (T; 5.5 min), cis-syn cyclobutyl thymine-thymine dimers (TT; 7.5 min), cyclobutyl uracil-thymine dimers (UT, the acid breakdown product of cytosine-thymine (CT) dimers; 9.5 min), and SP (14.5 min). The method was used to quantitate the amount of SP produced upon irradiation of B. subtilis spores and to monitor repair of SP in vivo by the enzyme SP lyase during spore germination.

Bacillus subtilis↗

PubMed1994

Deoxyhypusine synthase assay based on the use of polyhistidine-tagged substrate and metal chelate-affinity chromatography.

Hypusine formation on the eukaryotic initiation factor 5A (eIF-5A) precursor is a unique spermidine-dependent post-translational modification that appears to be ubiquitous in eukaryotic cells. In this modification, a specific lysine residue of eIF-5A precursor protein is first converted to deoxyhypusine by an addition of a butylamino group derived from spermidine; the deoxyhypusine residue is then hydroxylated to form hypusine. Deoxyhypusine synthase, an NAD(+)-dependent enzyme, catalyzes the first step of hypusine formation on the eIF-5A precursor. Since deoxyhypusine formation represents one of the most specific polyamine-dependent reactions in eukaryotic cells, the reaction may play an important role in cellular growth regulation. To facilitate the study of the function and significance of deoxyhypusine formation, we have developed a rapid and sensitive assay for deoxyhypusine synthase. The assay relied on the use of hexahistidine-tagged recombinant Neurospora 21-kDa eIF-5A precursor protein as the substrate protein. The radiolabeled polyhistidine-tagged protein, once modified by [3H]spermidine, was separated from free [3H]spermidine by a microscale metal-affinity chromatography in a dot blot filtration apparatus and quantified by liquid scintillation counting. The assay procedure is quick and simple compared to other methods reported in the literature. The sensitivity is limited by the specific activity of [3H]-spermidine in the reaction mixture. The metal-affinity chromatographic assay for deoxyhypusine synthase should facilitate the purification, characterization, and functional studies of this enzyme.

Chromatography, Affinity↗

PubMed1994

Radioassay of bifunctional 5-aminoimidazole-4-carboxamide ribotide transformylase-IMP cyclohydrolase by thin-layer chromatography.

A radioassay has been developed for the bifunctional enzyme, AICAR transformylase-IMP cyclohydrolase, which catalyzes reactions 9 and 10 of the de novo pathway for biosynthesis of purine nucleotides (AICAR-->FAICAR-->IMP). 3H-labeled AICAR or FAICAR is converted enzymically to product(s) which are separated by one-dimensional thin-layer chromatography prior to quantification by scintillation counting. Using this sensitive radioassay, a dissociation constant of IMP cyclohydrolase for FAICAR of 0.87 microM has been determined and AICAR, FAICAR, and IMP can be quantified in assay mixtures for AICAR transformylase-IMP cyclohydrolase. The ratio of specific enzymic activities for AICAR transformylase:IMP cyclohydrolase is 1:44.

Acyltransferases↗