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R L Kelley

Publications and source records attributed to R L Kelley.

At least 37 records · Page 2Linked to original sources
PubMed1995

The effect of chemical pretreatment on the aerobic microbial degradation of PCB congeners in aqueous systems.

A series of experiments was conducted to examine the effects of chemical pretreatment on biodegradation of 14C-labeled PCB congeners in aqueous systems. Fenton's reagent was used to generate hydroxyl radicals (OH) which were successful in partially oxidizing/transforming otherwise recalcitrant molecules of tetrachlorinated PCB, but had little or no impact on the biodegradation of a monochlorinated congener. Application of Fenton's reagent (1% H2O2, 1 mM FeSO4) followed by inoculation with pure cultures Pseudomonas sp, strain LB 400 and Alcaligenes eutrophus, strain H850 resulted in the removal of approximately 38% of 2-chlorobiphenyl and 51% of 2,2',4,4'-tetrachlorobiphenyl in the form of 14CO2. Comparison of the rate and extent of biodegradation of 2,2',4,4'-tetrachlorobiphenyl after the application of Fenton's reagent with the dynamic and final level of radioactivity in the aqueous phase of experimental system suggests two possible means of microbial utilization of tetrachlorinated PCB congener altered by chemical oxidation: (a) consumption of the partially oxidized chemical dissolved in the aqueous phase, and (b) direct microbial attack on the transformed compound, which may still be adhered to the solid surface.

Bacteria, Aerobic↗
PubMed1995

Maternal treatment with somatotropin alters embryonic development and early postnatal growth of pigs.

A possible management strategy to alter fetal development and enhance sow productivity and progeny performance was examined by maternal administration of porcine somatotropin during early gestation. Eighteen crossbred gilts were bred naturally to boars of similar genetics, and pregnancy was confirmed between Days 21 and 24 of gestation by ultrasound. All animals were allowed ad libitum consumption of a 16% CP gestation diet through Day 21 of gestation and 3.0 kg/d for the remainder of gestation. Gilts were injected twice daily with 0 (n = 10) or 15 micrograms/kg body weight (BW) (n = 10; total, 30 micrograms/kg BW per d) pituitary-derived porcine somatotropin (pST) during Days 28 to 40 of gestation. Data were collected postmortem during embryonic, neonatal, and market-weight phases. At 41 d of gestation, pST treatment increased embryonic survival (87.9 versus 77.0%; P < 0.05) and embryo crown rump lengths (77.96 versus 65.14 mm; P < 0.01), but embryo weight was not altered (10.15 and 9.03 g; P > 0.10). Pigs from pST-treated gilts had increased (P < 0.01) crown rump lengths at birth (31.5 versus 30.4 cm) and 21 d (50.9 versus 48.4 cm). However, no differences were observed in birth or 21-d weights as a result of pST treatment (P > 0.10). Neonatal carcasses of progeny (20 kg BW) from the pST-treated gilts had heavier semitendinosus muscles (76.1 versus 66.0 g; P < 0.10), larger longissimus muscle cross-sectional area (10.1 versus 8.2 cm2; P < 0.05), longer sides (51.2 versus 47.9 cm; P < 0.001), and decreased 10th rib backfat (6.67 versus 8.64 mm; P < 0.001) compared with those of controls. Carcasses of market-weight progeny (100 kg BW) from pST-treated gilts had larger longissimus muscle cross-sectional area (P < 0.10), heavier trimmed loins (P < 0.10), and longer carcass sides (P < 0.05). Data are supportive of a hypothesis that mechanisms during early embryonic development are sensitive to manipulation through selected management strategies of the sow and that modifications of this strategy may serve as a model for the examination of molecular and cellular events controlling early embryonic growth.

Animals↗
PubMed1993

Initial organization of the Drosophila dorsoventral axis depends on an RNA-binding protein encoded by the squid gene.

Females mutant for the newly identified squid (sqd) gene are sterile and lay eggs that display only dorsal structures. The resulting embryos are also dorsalized even if fertilized by wild-type sperm. The gene acts midway through oogenesis at about the time dorsoventral (D/V) axis is established within the growing egg chamber. The sqd gene encodes at least three distinct proteins generated by alternative RNA processing that are members of a well-characterized family of RNA-binding proteins. At least one Sqd isoform is essential in somatic tissues. The ventralizing mutations gurken (grk), torpedo (tor), and cornichon are all epistatic to sqd. Strong alleles of grk and top can act as dominant suppressors of sqd dorsalization. A model of D/V axis formation is presented postulating that squid is needed to organize a concentration gradient of a morphogen originating in the germinal vesicle.

Alleles↗
PubMed1992

Differences in GH secretion from individual somatotropes in rats genetically selected for fast and slow growth.

A reverse hemolytic plaque assay was used to examine effects of selection for fast (F) and slow (S) growth on growth hormone (GH) secretion by individual somatotropes. Anterior pituitaries (AP) from 32 male Charles River CD strain rats selected for F and S growth for 20 generations were used. Four rats per line were used at 4, 6, 8, or 10 wk of age. Body weight (P < 0.0001) of F rats was greater compared with S rats. AP (P < 0.05) were heavier at 8 and 10 wk of age in F compared with S line rats. Percentages of GH-secreting cells were unaffected by age (range = 32.7-35.5%) and line [F = 33.1 +/- 1.2% (SE) vs. S = 34.5 +/- 1.2%] or by human GH-releasing factor (hGRF). At 8 and 10 wk, mean plaque-forming area was greater (P < 0.0001) in F compared with S rats under both nonstimulated (2,704 +/- 202 vs. 1,648 +/- 202 microns2) and hGRF-stimulated secretion (4,503 +/- 202 vs. 2,682 +/- 202 microns2). Results indicate that differences in growth observed in the two lines may be due to a greater secretory capacity of individual somatotropes rather than to a greater percentage of somatotropes or sensitivity of somatotropes to secretagogue.

Aging↗
PubMed1992

Characterization of human monoclonal antibodies directed against hepatitis B surface antigen.

Four hybridoma cell lines stably secreting human monoclonal antibodies directed against hepatitis B surface antigen have been isolated. The monoclonal antibodies have been characterized by determining several allotypes, measuring affinity for HBsAg, binding to two HBsAg subtypes, and kinetics of antibody binding to solid adsorbed antigen. In addition, the relative position of the epitopes have been determined by competition in binding to HBsAg. The results indicate that human anti-HBsAg monoclonal antibodies of quite different properties can be isolated. Pharmacokinetics of one antibody have been measured in two rhesus monkeys. This monoclonal antibody, OST 577, has been compared to hyperimmune gamma globulins in a Bureau of Biologics approved radioimmunoassay. It is expected that these antibodies will be useful in preventing and treating hepatitis B.

Animals↗
PubMed1990

Lignin peroxidase-negative mutant of the white-rot basidiomycete Phanerochaete chrysosporium.

Phanerochaete chrysosporium produces two classes of extracellular heme proteins, designated lignin peroxidases and manganese peroxidases, that play a key role in lignin degradation. In this study we isolated and characterized a lignin peroxidase-negative mutant (lip mutant) that showed 16% of the ligninolytic activity (14C-labeled synthetic lignin----14CO2) exhibited by the wild type. The lip mutant did not produce detectable levels of lignin peroxidase, whereas the wild type, under identical conditions, produced 96 U of lignin peroxidase per liter. Both the wild type and the mutant produced comparable levels of manganese peroxidase and glucose oxidase, a key H2O2-generating secondary metabolic enzyme in P. chrysosporium. Fast protein liquid chromatographic analysis of the concentrated extracellular fluid of the lip mutant confirmed that it produced only heme proteins with manganese peroxidase activity but no detectable lignin peroxidase activity, whereas both lignin peroxidase and manganese peroxidase activities were produced by the wild type. The lip mutant appears to be a regulatory mutant that is defective in the production of all the lignin peroxidases.

Basidiomycota↗
PubMed1989

Mutations in nuclear gene cyt-4 of Neurospora crassa result in pleiotropic defects in processing and splicing of mitochondrial RNAs.

The nuclear cyt-4 mutants of Neurospora crassa have been shown previously to be defective in splicing the group I intron in the mitochondrial large rRNA gene and in 3' end synthesis of the mitochondrial large rRNA. Here, Northern hybridization experiments show that the cyt-4-1 mutant has alterations in a number of mitochondrial RNA processing pathways, including those for cob, coI, coII and ATPase 6 mRNAs, as well as mitochondrial tRNAs. Defects in these pathways include inhibition of 5' and 3' end processing, accumulation of aberrant RNA species, and inhibition of splicing of both group I introns in the cob gene. The various defects in mitochondrial RNA synthesis in the cyt-4-1 mutant cannot be accounted for by deficiency of mitochondrial protein synthesis or energy metabolism, and they suggest that the cyt-4-1 mutant is defective in a component or components required for processing and/or turnover of a number of different mitochondrial RNAs. Defective splicing of the mitochondrial large rRNA intron in the cyt-4-1 mutant may be a secondary effect of failure to synthesize pre-rRNAs having the correct 3' end. However, a similar explanation cannot be invoked to account for defective splicing of the cob pre-mRNA introns, and the cyt-4-1 mutation may directly affect splicing of these introns.

Blotting, Northern↗
PubMed1989

Characterization of mutant mitochondrial plasmids of Neurospora spp. that have incorporated tRNAs by reverse transcription.

The Mauriceville and Varkud mitochondrial plasmids of Neurospora spp. are closely related, closed-circular DNAs (3.6 and 3.7 kilobases, respectively) whose nucleotide sequences and genetic organization suggest relationships to mitochondrial introns and retroelements. We have characterized nine suppressive mutants of these plasmids that outcompete mitochondrial DNA and lead to impaired growth. All nine suppressive plasmids contain small insertions, corresponding to or including a mitochondrial tRNA (tRNATrp, tRNAGly, or tRNAVal) or a tRNA-like sequence. The insertions are located at the position corresponding to the 5' end of the major plasmid transcript or 24 nucleotides downstream near a cognate of the sequence at the major 5' RNA end. The structure of the suppressive plasmids suggests that the tRNAs were inserted via an RNA intermediate. The 3' end of the wild-type plasmid transcript can itself be folded into a secondary structure which has tRNA-like characteristics, similar to the tRNA-like structures at the 3' ends of plant viral RNAs. This structure may play a role in replication of the plasmids by reverse transcription. Major transcripts of the suppressive plasmids begin at the 5' end of the inserted mitochondrial tRNA sequence and are present in 25- to 100-fold-higher concentrations than are transcripts of wild-type plasmids. Mapping of 5' RNA ends within the inserted mtDNA sequences identifies a short consensus sequence (PuNPuAG) which is present at the 5' ends of a subset of mitochondrial tRNA genes. This sequence, together with sequences immediately upstream in the plasmids, forms a longer consensus sequence, which is similar to sequences at transcription initiation sites in Neurospora mitochondrial DNA. The suppressive behavior of the plasmids is likely to be directly related to the insertion of tRNAs leading to overproduction of plasmid transcripts.

DNA Mutational Analysis↗
PubMed1989

Involvement of tyrosyl-tRNA synthetase in splicing of group I introns in Neurospora crassa mitochondria: biochemical and immunochemical analyses of splicing activity.

We reported previously that mitochondrial tyrosyl-tRNA synthetase, which is encoded by the nuclear gene cyt-18 in Neurospora crassa, functions in splicing several group I introns in N. crassa mitochondria (R. A. Akins and A. M. Lambowitz, Cell 50:331-345, 1987). Two mutants in the cyt-18 gene (cyt-18-1 and cyt-18-2) are defective in both mitochondrial protein synthesis and splicing, and an activity that splices the mitochondrial large rRNA intron copurifies with a component of mitochondrial tyrosyl-tRNA synthetase. Here, we used antibodies against different trpE-cyt-18 fusion proteins to identify the cyt-18 gene product as a basic protein having an apparent molecular mass of 67 kilodaltons (kDa). Both the cyt-18-1 and cyt-18-2 mutants contain relatively high amounts of inactive cyt-18 protein detected immunochemically. Biochemical experiments show that the 67-kDa cyt-18 protein copurifies with splicing and synthetase activity through a number of different column chromatographic procedures. Some fractions having splicing activity contain only one or two prominent polypeptide bands, and the cyt-18 protein is among the few, if not only, major bands in common between the different fractions that have splicing activity. Phosphocellulose columns resolve three different forms or complexes of the cyt-18 protein that have splicing or synthetase activity or both. Gel filtration experiments show that splicing activity has a relatively small molecular mass (peak at 150 kDa with activity trailing to lower molecular masses) and could correspond simply to dimers or monomers, or both, of the cyt-18 protein. Finally, antibodies against different segments of the cyt-18 protein inhibit splicing of the large rRNA intron in vitro. Our results indicate that both splicing and tyrosyl-tRNA synthetase activity are associated with the same 67-kDa protein encoded by the cyt-18 gene. This protein is a key constituent of splicing activity; it functions directly in splicing, and few, if any, additional components are required for splicing the large rRNA intron.

Amino Acyl-tRNA Synthetases↗
PubMed1988

The Drosophila su(Hw) gene, which controls the phenotypic effect of the gypsy transposable element, encodes a putative DNA-binding protein.

Homozygous mutations at the suppressor of Hairy-wing [su(Hw)] locus reverse the phenotype of gypsy-induced alleles in a number of genes located throughout the Drosophila genome. To understand the molecular basis of this phenomenon, the su(Hw) locus was isolated by chromosomal walking from a cloned homeo-box-containing sequence. The exact location of the gene was determined by Southern analysis of the DNA alterations associated with several su(Hw) alleles. A 9.5-kb KpnI-SalI fragment, where all the DNA changes associated with su(Hw) mutations were mapped, was able to rescue the su(Hw) mutant phenotype after P-element-mediated germ-line transformation. This DNA fragment encodes a 3.3-kb RNA that is expressed in all stages of Drosophila development; the size or abundance of this RNA is affected in several su(Hw) alleles tested. This transcript encodes a protein that contains a highly acidic region and 12 repeats of the 'Zn finger' domain characteristic of some DNA-binding and transcription-activating proteins, supporting the hypothesis that the su(Hw) locus might encode a transcription factor that plays a role in the expression of the gypsy element.

Alleles↗
PubMed1986

Mitochondrial plasmids of Neurospora: integration into mitochondrial DNA and evidence for reverse transcription in mitochondria.

The Mauriceville (3.6 kb) and Varkud (3.8 kb) mitochondrial plasmids of Neurospora are closely related, closed circular DNAs whose nucleotide sequences and genetic organization suggest relationships to mitochondrial introns and retrotransposons. Here we isolated mutants whose growth is impaired as a result of malevolent behavior of these plasmids. All 12 mutants contain variant plasmids that are suppressive relative to mtDNA, and ten also contain defective mtDNAs. All the suppressive plasmids contain small insertions, generally including a mitochondrial tRNA sequence, at or near the major 5' RNA start site. The structure of the suppressive plasmids suggests that they were generated via an RNA intermediate and a reverse transcription step. At least three of the mutants contain defective mtDNAs into which mitochondrial plasmid sequences have integrated. Sequences at the plasmid-mtDNA junctions are also consistent with integration via an RNA intermediate.

Chromosome Mapping↗
PubMed1986

Purification and characterization of glucose oxidase from ligninolytic cultures of Phanerochaete chrysosporium.

Glucose oxidase, an important source of hydrogen peroxide in lignin-degrading cultures of Phanerochaete chrysosporium, was purified to electrophoretic homogeneity by a combination of ion-exchange and molecular sieve chromatography. The enzyme is a flavoprotein with an apparent native molecular weight of 180,000 and a denatured molecular weight of 80,000. This enzyme does not appear to be a glycoprotein. It gives optimal activity with D-glucose, which is stoichiometrically oxidized to D-gluconate. The enzyme has a relatively broad pH optimum of 4 to 5. It is inhibited by Ag+ (10 mM) and o-phthalate (100 mM), but not by Cu2+, NaF, or KCN (each 10 mM).

Basidiomycota↗
PubMed1985

Lack of lignin degradation by glucose oxidase-negative mutants of Phanerochaete chrysosporium.

Glucose oxidase-negative (gox-) mutants of Phanerochaete chrysosporium were isolated after exposing conidia to UV irradiation. The gox- mutants exhibited little or no ability to degrade lignin (2-[14C]-synthetic lignin to 14CO2); however, they retained other secondary metabolic features such as the ability to conidiate and produce veratryl alcohol, suggesting that they are not pleiotropic for secondary metabolism. Lignin degradation activity was restored in gox+ revertants. These results, in support of earlier evidence, indicate that glucose oxidase activity plays an important role in lignin degradation by P. chrysosporium.

Basidiomycota↗
PubMed1985

Mutational studies with the trp repressor of Escherichia coli support the helix-turn-helix model of repressor recognition of operator DNA.

Several classes of trp repressor mutants were selected and analyzed in vivo. Mutants that produced repressors with either enhanced or reduced activity were obtained. One class of mutants produced inactive or slightly active repressors that were trans-dominant to the wild-type repressor. The amino acid substitutions in many of these repressors were clustered in a segment of the polypeptide that is homologous to the DNA recognition domain of the lambda cro repressor. A second functionally important region of the trp repressor was identified; this region could participate in L-tryptophan binding. Observations with trpR nonsense mutants suggest that the first 67 residues of the repressor polypeptide are sufficient for subunit association.

Amino Acid Sequence↗
PubMed1984

Repression is relieved before attenuation in the trp operon of Escherichia coli as tryptophan starvation becomes increasingly severe.

Expression of the tryptophan operon of Escherichia coli is regulated over about a 500- to 600-fold range by the combined action of repression and attenuation. Repression regulates transcription initiation in response to variation in the intracellular concentration of tryptophan. Attenuation regulates transcription termination at a site in the leader region of the operon in response to changes in the extent of charging of tRNATrp. We measured repression independently of attenuation to ascertain whether these regulatory mechanisms were used differentially by the bacterium as the severity of tryptophan starvation was increased. We found that repression regulated transcription of the operon over the range from growth with excess tryptophan to growth under moderate tryptophan starvation. By contrast, attenuation (termination control) was not relaxed until tryptophan starvation was in the moderate-to-severe range. Thus, attenuation and repression were used to regulate transcription in response to different degrees of tryptophan deprivation. Consistent with this conclusion is the observation that when tryptophan starvation was sufficient to relieve repression 50 to 60%, 65% of the tRNATrp of the bacterium was charged. These findings provide a possible explanation for the existence of only two tryptophan codons in the coding region for the trp leader peptide of Enterobacteriaceae.

Bacteriophage lambda↗