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J D Jones

Publications and source records attributed to J D Jones.

At least 109 records · Page 6Linked to original sources
PubMed1994

Analysis of the chromosomal distribution of transposon-carrying T-DNAs in tomato using the inverse polymerase chain reaction.

We are developing a system for isolating tomato genes by transposon mutagenesis. In maize and tobacco, the transposon Activator (Ac) transposes preferentially to genetically linked sites. To identify transposons linked to various target genes, we have determined the RFLP map locations of Ac- and Dissociation (Ds)-carrying T-DNAs in a number of transformants. T-DNA flanking sequences were isolated using the inverse polymerase chain reaction (IPCR) and located on the RFLP map of tomato. The authenticity of IPCR reaction products was tested by several criteria including nested primer amplification, DNA sequence analysis and PCR amplification of the corresponding insertion target sequences. We report the RFLP map locations of 37 transposon-carrying T-DNAs. We also report the map locations of nine transposed Ds elements. T-DNAs were identified on all chromosomes except chromosome 6. Our data revealed no apparent chromosomal preference for T-DNA integration events. Lines carrying transposons at known map locations have been established which should prove a useful resource for isolating tomato genes by transposon mutagenesis.

Base Sequence↗
PubMed1994

Is the plasma amino acid consumption test an accurate test of exocrine pancreatic insufficiency?

BACKGROUND/AIMS: The amino acid consumption test has been proposed as an accurate test of exocrine pancreatic function. The diagnostic accuracy of this test was determined by simultaneously measuring plasma amino acids and enzyme secretion during stimulation of the pancreas with cholecystokinin octapeptide (CCK-OP) in 60 consecutive patients suspected of having pancreatic insufficiency. METHODS: All patients underwent duodenal intubation and intravenous infusion of CCK-OP (40 ng.kg-1.h-1). Pancreatic enzyme (lipase and trypsin) outputs and plasma amino acids were measured for a period of 1 hour. Total and individual plasma amino acids were quantitated by ion-exchange chromatography. The severity of pancreatic insufficiency was graded on the basis of enzyme output during CCK-OP infusion. RESULTS: There was no relationship between pancreatic enzyme output and plasma concentrations of individual or total amino acids before or during CCK-OP stimulation. Using a total amino acid decrease of 12% as the cutoff, the amino acid consumption test was 91% sensitive, but very nonspecific (21% specificity) for detection of pancreatic insufficiency. CONCLUSIONS: The amino acid consumption test with CCK-OP stimulation does not discriminate between patients with normal and impaired exocrine pancreatic secretion.

Adult↗
PubMed1994

Effect of charged residue substitutions on the membrane-interactive properties of signal sequences of the Escherichia coli LamB protein.

Although the central role of the signal sequence in protein export is well established, the molecular details underlying signal sequence in vivo function remain unclear. As part of our continuing effort to relate signal sequence phenotypes to specific biophysical properties, we have carried out an extensive characterization of the secondary structure and lipid interactions for a family of peptides corresponding to the wild-type E. coli LamB signal sequence, and mutants that harbor charged residue point mutations in the hydrophobic core region. We used membrane-resident fluorescence quenching according to the parallax method to determine the relative depth of insertion of tryptophan-labeled analogs of these peptides into the acyl chain region of bilayer vesicles composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol. Also, restriction of acyl chain motion upon peptide binding was evaluated using steady-state fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene. Each of these peptides showed evidence of insertion into the acyl chain region, although most likely not in a transmembrane orientation. The mutant peptides were shown to have a reduced insertion potential relative to the wild-type peptide. Furthermore, tryptophan spectral properties indicated that insertion of the wild-type and mutant peptides enhances bilayer hydration. This effect was particularly pronounced with peptides harboring negatively charged aspartate point substitutions. The results are discussed in relation to the potential roles of signal sequences in mediating protein translocation.

Amino Acid Sequence↗
PubMed1994

Effect of charged residue substitutions on the thermodynamics of signal peptide-lipid interactions for the Escherichia coli LamB signal sequence.

We have used tryptophan fluorescence spectroscopy to characterize the binding affinities of an Escherichia coli LamB signal peptide family for lipid vesicles. These peptides harbor charged residue substitutions in the hydrophobic core region. Titrations of peptides with vesicles composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine and 1-palmitoyl-2-oleoyl-sn-3-phosphoglycerol (65:35 mol%), in conjunction with evaluation of peptide dissociation rates from these vesicles, were used to determine binding parameters quantitatively. We find that under low ionic strength conditions, point mutations introducing negatively charged aspartate residues substantially reduce peptide affinity relative to the wild-type peptide. However, the difference between wild-type and mutant peptide affinities was much lower under approximately physiological ionic strength. In addition, the lipid affinities of model surface-binding and transmembrane peptides were determined. These comparative studies with signal and model peptides permitted semi-quantitative deconvolution of signal peptide binding into electrostatic and hydrophobic components. We find that both interactions contribute significantly to binding, although the theoretically available hydrophobic free energy is largely offset by unfavorable polar-group effects. The implications of these results for understanding the potential roles of the signal sequence in protein translocation are discussed.

Amino Acid Sequence↗
PubMed1994

Circulating cytokine levels in osteoporotic and normal women.

Interleukin-1 (IL-1) and IL-6 have been postulated to play roles in the pathogenesis of postmenopausal osteoporosis. To test this hypothesis, we measured circulating levels of IL-6, IL-1 alpha, and IL-1 beta in 40 age-matched normal and 40 osteoporotic women with vertebral fractures and increased bone turnover. Since IL-1 activity is modulated by the IL-1 receptor antagonist (IL-1ra), we also measured circulating IL-1ra levels in these women. Despite having higher rates of bone turnover as assessed by bone biochemical markers, the osteoporotic women had serum levels of IL-6, IL-1 alpha, and IL-1 beta that were similar to the normal women. IL-1ra levels (mean +/- SEM) tended to be lower in the osteoporotic women (143 +/- 21 pg/mL) vs. the normal women (189 +/- 22 pg/mL; P = 0.08). The IL-1 alpha/IL-1ra ratio, an index of IL-1 alpha bioactivity, was higher in the osteoporotic women (6.4 +/- 1.1) than in the normal women (4.4 +/- 0.5; P < 0.05). There were nonsignificant trends for increased IL-1 beta/IL-1ra and (IL-1 alpha + IL-1 beta)/IL-1ra ratios in the osteoporotic vs. normal women. None of the cytokines correlated with markers of bone resorption in either group of women. In summary, although there was a trend for a higher IL-1/IL-1ra ratio in the osteoporotic women, we were unable to demonstrate unequivocal abnormalities of cytokines affecting bone resorption in peripheral serum of women with postmenopausal osteoporosis. However, it is possible that increased production of these cytokines occurs in the local environment of bone or bone marrow and is not detected by analysis of peripheral serum. Thus, further studies will be required to exclude this possibility.

Aged↗
PubMed1994

Bone resorption in healthy and osteoporotic postmenopausal women: comparison markers for serum carboxy-terminal telopeptide of type I collagen and urinary pyridinium cross-links.

We compared two highly specific markers for bone resorption-pyridinium cross-links (pyridinoline (PYR) and deoxypyridinoline (DPR)) in urine and carboxy-terminal telopeptide of type I collagen (ICTP) in serum-in 63 healthy postmenopausal women and 63 women with osteoporosis characterized by more bone resorption than bone formation. The ICTP, PYR and DPR levels were all higher, by 24% (p = 0.001), 16% (p = 0.05) and 25% (p = 0.004), respectively, in the osteoporotic women. For the merged groups, there were significant correlations between serum ICTP concentration and urinary PYR (r = 0.667, p < 0.0001) and DPR (r = 0.452, p < 0.0001) excretion; for the osteoporotic and normal women separately, the r values were 0.73 (p < 0.01) and 0.45 (p < 0.01) for PYR and 0.51 (p < 0.01) and 0.22 (p = 0.08) for DPR versus ICTP respectively. Weak correlations in linear regression between ICTP and various indices of bone formation (osteocalcin, bone-specific alkaline phosphatase and carboxy-terminal propeptide of type I procollagen) disappeared when the correlation between ICTP and pyridinolines was accounted for by calculation of partial correlation coefficients in multiple regression analysis. Serum ICTP concentration appears to discriminate between groups of normal and osteoporotic women as well as urinary pyridinium cross-links, which is thus far the most sensitive method for assessing bone resorption.

Aged↗
PubMed1994

Osteoporosis and periodontal disease: a review.

A review of the literature on the relationship between osteoporosis and periodontal disease is presented. Osteoporosis, a metabolic disease, and periodontal disease, which is infectious, are both major health problems with multifactorial etiologies. There is histologic and radiographic evidence from animals and humans that osteoporosis does affect alveolar bone by decreasing bone mass and trabeculation. The literature reviewed in this paper suggests, but does not yet provide conclusive evidence for, a direct relationship between osteoporosis and periodontal disease.

Aged↗
PubMed1993

Membrane-bound conformation of a signal peptide: a transferred nuclear Overhauser effect analysis.

We have determined the conformation of an analogue of the Escherichia coli LamB signal peptide inserted into a model membrane using the transferred nuclear Overhauser effect (trNOE) NMR technique. In order to make NMR analysis feasible, a water-soluble LamB signal peptide analogue was designed by inserting three basic residues (KRR) into the N-terminal region of the wild-type sequence (with a Val-->Trp mutation for fluorescence measurements), viz., MMITLRKRRKLPLAVAVAAGWMSAQAMA-NH2. For the purpose of the trNOE study, the binding affinity of the peptide for phospholipid vesicles was tuned by adjusting the proportion of acidic lipid in the vesicle. Circular dichroism and fluorescence measurements showed that the KRR-LamB signal peptide spontaneously inserted into the lipid bilayer with a conformational transition from a mostly random coil to a predominantly alpha-helical structure. The trNOE analysis revealed that the alpha-helix extended from approximately the beginning of the hydrophobic core (residue Leu8) to the C-terminus. The continuity of the helix was somewhat disrupted at the end of the hydrophobic core (around residue Gly17). Furthermore, the topological arrangement of the peptide within the lipid bilayer was explored by NMR line broadening induced by a paramagnetic nitroxide-labeled lipid. The line-broadening results demonstrated that the residues in the helical region are well integrated into the acyl chain region of the bilayer. The N-terminal part of the peptide showed many trNOEs, but without any indication of a helical conformation. The line-broadening analysis indicates that this part of the peptide primarily interacts with the membrane surface.

Amino Acid Sequence↗
PubMed1993

High level expression of the Activator transposase gene inhibits the excision of Dissociation in tobacco cotyledons.

A fusion of the strong cauliflower mosaic virus 35S promoter to the Activator (Ac) transposase (TPASE) gene does not trigger excision of Dissociation (Ds) continuously during tobacco cotyledon development, although once activated, the 35S promoter remains active throughout embryogeny. Epistasis studies where 35S:TPASE is in trans with later-acting fusions indicate that transient effectiveness for excision results from this fusion inhibiting its own action and that of other TPASE sources. Inhibition depends on the strength of TPASE expression, since fusions of the 35S promoter to a TPASE cDNA accumulate 30-fold lower amounts of TPASE mRNA than the 35S:TPASE gene fusion and do not inhibit excision. We discuss the role of TPASE levels in the curious relationship between Ac activity and Ac dosage in maize.

Base Sequence↗
PubMed1993

Effects of gene dosage and sequence modification on the frequency and timing of transposition of the maize element Activator (Ac) in tobacco.

The effect of Ac copy number on the frequency and timing of germinal transposition in tobacco was investigated using the streptomycin phosphotransferase gene (SPT) as an excision marker. The activity of one and two copies of the element was compared by selecting heterozygous and homozygous progeny of transformants carrying single SPT::Ac inserts. It was observed that increasing gene copy not only increases the transposition frequency, but also occasionally alters the timing of transposition such that earlier events are obtained. The result is that some homozygous plants generate multiple streptomycin resistant progeny carrying the same transposed Ac (trAc) element. We have also investigated the effect of modification of the sequence in the region around 82 bp downstream of the polyadenylation site and 177 bp from the 3' end of the element on germinal excision frequencies. Alteration of three bases to create a Bgl II site at this location caused a minor decrease in germinal excision events, but insertion of four bases to create a Cla I site caused a 10-fold decrease in the transposition activity of the Ac element.

Agrobacterium tumefaciens↗
PubMed1993

A genetic analysis of DNA sequence requirements for Dissociation state I activity in tobacco.

Our objective was to test whether the double Ds structure correlated with Dissociation state I activity (i.e., high frequency of chromosome breakage and low frequency of reversion) in maize exhibited similar properties in tobacco. A genetic assay was established to test double Ds and related structures for their ability to cause loss of the linked marker genes streptomycin phosphotransferase and beta-glucuronidase in transgenic tobacco. An engineered double Ds element and a simple Ds element showed behavior consistent with that of state I and state II Ds elements, respectively, as described for maize. DNA structural rearrangements accompanied marker gene loss. Dissection of the double Ds structure showed that a left end and a right end of Ds in direct orientation were sufficient for the instability observed. This result suggested that left and right ends of Ds in direct orientation can participate in aberrant transposition events, consistent with two different models for double Ds-induced chromosome breakage proposed previously. Both models predict that the inversion of a half Ds element accompanies the aberrant transposition event. Such an inversion was detected by polymerase chain reaction experiments in tobacco and maize only when Activator activity was present in the genome.

Base Sequence↗
PubMed1993

Heterologous transposon tagging of the DRL1 locus in Arabidopsis.

The development of heterologous transposon tagging systems has been an important objective for many laboratories. Here, we demonstrate the use of a Dissociation (Ds) derivative of the maize transposable element Activator (Ac) to tag the DRL1 locus of Arabidopsis. The drl1 mutant shows highly abnormal development with stunted roots, few root hairs, lanceolate leaves, and a highly enlarged, disorganized shoot apex that does not produce an inflorescence. The mutation was shown to be tightly linked to a transposed Ds, and somatic instability was observed in the presence of the transposase source. Some plants showing somatic reversion flowered and produced large numbers of wild-type progeny. These revertant progeny always inherited a DRL1 allele from which Ds had excised. Analysis of the changes in DNA sequence induced by the insertion and excision of the Ds element showed that they were typical of those induced by Ac and Ds in maize.

Arabidopsis↗
PubMed1993

Alkali treatment for rapid preparation of plant material for reliable PCR analysis.

For plant genetics, it would be useful to monitor easily the segregation of different alleles using the polymerase chain reaction (PCR). Preparation of DNA templates from individual plants needs to be rapid and reliable. A one tube protocol is described that involves subjecting plant tissue pieces to alkali, neutralization and heat denaturation prior to PCR analysis, and that proved to be much faster and more reliable than published protocols.

Alkalies↗
PubMed1993

Short-term effects of recombinant human insulin-like growth factor I on bone turnover in normal women.

Because insulin-like growth factor I (IGF-I) is a potent stimulator of osteoblast proliferation, it has potential in the treatment of osteoporosis. However, IGF-I affects multiple organ systems, and it is unclear whether treatment can stimulate bone formation without producing unacceptable side effects. Therefore, we evaluated the effects of treatment with recombinant human IGF-I in 18 postmenopausal women who received various dosages (30, 60, 120, or 180 micrograms/kg.day) by sc injections for 6 days. Serum IGF-I concentrations increased by 2- to 4-fold during treatment. There were dose-dependent increases in serum type I procollagen carboxyl-terminal propeptide concentration (r = 0.85, P < 0.001), an index of collagen synthesis, and of urinary excretion of deoxypyridinoline (r = 0.75, P = 0.001), an index of bone collagen breakdown. At the two higher dosages, recombinant human IGF-I caused orthostatic hypotension, sinus tachycardia, bilateral parotid discomfort, weight gain, and edema in some women. Hypoglycemia did not occur. However, treatment at the 2 lower dosages increased serum type I procollagen carboxyl-terminal propeptide significantly and produced minimal or no side effects. Long-term studies on the effects and the safety of low dosage recombinant human IGF-I on bone mass should now be undertaken in osteoporotic women.

Aged↗
PubMed1992

Development of an efficient two-element transposon tagging system in Arabidopsis thaliana.

Modified Ac and Ds elements, in combination with dominant markers (to facilitate monitoring of excision, reinsertion and segregation of the elements) were introduced into Arabidopsis thaliana ecotype Landsberg erecta. The frequencies of somatic and germinal transactivation of the Ds elements were monitored using a streptomycin resistance assay. Transactivation was significantly higher from a stable Ac (sAc) carrying a 537 bp deletion of the CpG-rich 5' untranslated leader of the transposase mRNA than from a wild-type sAc. However, substitution of the central 1.77 kb of the transposase open reading frame (ORF) with a hygromycin resistance marker did not alter the excision frequency of a Ds element. beta-Glucuronidase (GUS) or iaaH markers were linked to the transposase source to allow the identification of plants in which the transposase source had segregated away from the transposed Ds element, eliminating the possibility of somatic or germinal re-activation. Segregation of the excision marker, Ds and sAc was monitored in the progeny of plants showing germinal excision of Ds. 29% of the plants inheriting the excision marker carried a transposed Ds element.

Blotting, Southern↗
PubMed1992

Effective vectors for transformation, expression of heterologous genes, and assaying transposon excision in transgenic plants.

Progress in plant molecular biology has depended heavily on the availability of effective vectors for plant cell transformation and heterologous expression. In this paper we describe the structures of a wide array of plasmids which have proved extremely effective in (a) plant transformation, (b) expression of heterologous genes and (c) assaying the activity of transposons in transgenic plants. Constructs that confer resistance to kanamycin, hygromycin, streptomycin, spectinomycin and phosphinotricin, or that confer beta-glucuronidase (GUS) gene expression are presented. Binary vector constructs that carry polylinkers of the pUC and Bluescript types are also described. Plasmids that permit the expression of any heterologous reading frame from either nopaline synthase (nos) or octopine synthase (ocs) promoters, as well as the cauliflower mosaic virus 35S promoter, using either the nopaline synthase or octopine synthase 3' polyadenylation sequences, are presented. These constructs permit a choice of orientation of the resulting transgene of interest, relative to the orientation of the selection marker gene. Most of the plasmids described here are publicly available.

Amino Acid Oxidoreductases↗