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Biomedical subjects

H D Jones

Publications and source records attributed to H D Jones.

At least 19 recordsLinked to original sources
PubMed2001

Age-dependent transformation frequency in elite wheat varieties.

Wheat is a major world crop and as such is a primary target for improvement of agronomic characteristics via genetic engineering. Optimization of transformation is essential in order to overcome the relatively low transformation frequencies encountered with wheat. Transformation of elite wheat varieties is not always successful due to variability in regeneration and transformation frequencies between varieties. In this work, two elite wheat varieties with a relatively high embryogenic capacity were transformed by particle bombardment. A strong correlation between transformation frequency and the age of wheat donor plants was observed in both varieties. The mean transformation frequency rose from 0.7% to 5% when using immature embryos from old and young donor plants, respectively. This was observed in both varieties, the best bombardments achieving up to 7.3% frequency. Using explants at an optimal developmental stage from donor plants grown under environmentally-controlled conditions has improved the reproducibility of transformation efficiency of elite wheat varieties and leads to the production of apparently phenotypically normal, fertile, transgenic plants.

Base Sequence↗
PubMed2001

Factors influencing Agrobacterium-mediated transient expression of uidA in wheat inflorescence tissue.

A critical step in the development of Agrobacterium tumifaciens-mediated transformation is the establishment of optimal conditions for T-DNA delivery into tissue from which whole plants can be regenerated. The efficient transformation of inflorescence tissue from 'Baldus', a commercial wheat variety, using the Agrobacterium strain AGLI harbouring the binary vector pAL156 is reported here. The effects of various factors on delivery and the transient expression of the uidA gene were studied including the duration of preculture, vacuum infiltration, the effect of sonication treatments, and Agrobacterium cell density. Optimal T-DNA delivery (as measured by uidA activity) was obtained from inflorescence tissues precultured for 21 d and sonicated. Increasing Agrobacterium cell density, the duration of inoculation/co-cultivation, and vacuum pressure, up to a threshold, increased uidA expression. The investigation of factors that influence T-DNA delivery is an important first step in the utilization of Agrobacterium in the transformation of immature wheat inflorescence tissue.

Agrobacterium tumefaciens↗
PubMed2000

A quality improvement approach to reducing use of meperidine.

BACKGROUND: In 1991 the University of Wisconsin Hospital and Clinics formed a pain management QI team whose goal was to improve pain management through education, outcome monitoring, and the development of programs intended to improve clinical practice. Longitudinal monitoring mechanisms were established to audit medical records and survey patients to examine both staff practice patterns and patient outcomes. The QI team targeted use of meperidine, one of the most widely used opioid analgesics for the treatment of moderate to severe pain, which is now discouraged as a first-line agent for most painful conditions. IMPLEMENTING THE QI PROCESS: A QI process was implemented using a traditional plan-do-check-act (PDCA) model, resulting in a successful and sustained reduction of inappropriate meperidine use. A cause-and-effect diagram helped highlight the multiple factors contributing to the drug's overuse and was used to prioritize targets for action. A flow chart helped to uncover some of the interrelationships between the myths about meperidine and the resultant customary prescribing and administration practices. While most of the strategies were implemented in 1996 (formulary guideline release, change in stock supply and physician orders, staff education and feedback), a significant impact in practice was not seen until late 1997. Ongoing tracking and feedback loops were established to ensure continued low use of meperidine. CONCLUSION: Use of a QI approach in pain management has been shown to affect the visibility of pain as a clinical priority, enhance interdisciplinary collaboration, facilitate the implementation of clinical guidelines at the bedside, and improve the quality of care for patients.

Analgesics, Opioid↗
PubMed2000

Identification and analysis of proteins that interact with the Avena fatua homologue of the maize transcription factor VIVIPAROUS 1.

The Avena fatua (wild oat) homologue of VIVIPAROUS 1 (AfVP1) has been implicated in controlling the maintenance of embryo dormancy in mature imbibed seeds, but the detailed mechanisms by which this transcription factor family activates embryo maturation pathways and simultaneously represses germination are not known. A two-hybrid screen in yeast identified three proteins that interacted specifically with AfVP1 (AfVP1 interacting proteins; AfVIPs). AfVIPs 2 and 3 interacted with the C-terminus of AfVP1, which contains the B2 + B3 domains, previously shown to bind DNA, whereas AfVIP1 interacted with the isolated B3 domain. Using purified proteins in in vitro experiments, all three AfVIPs were shown also to interact with the Arabidopsis homologue ABSCISIC ACID INSENSITIVE 3 (ABI3). The three AfVIPs were expressed in both dormant and non-dormant embryos, but the abundance of AfVIP1 and 3 transcripts was greater in germinated than dormant seeds, whereas transcripts of AfVIP2 (and AfVP1) were more highly expressed in dormant embryos. The AfVIP3 protein has homology to a human cell-crisis gene with a predicted role in the cell cycle; AfVIP2 contains a ring-type zinc finger motif. These homologies, together with analysis of expression studies, suggest that these proteins may play specific roles in AfVP1-mediated regulation of the dormancy to germination transition in A. fatua seeds.

Amino Acid Sequence↗
PubMed2000

Interactions of the developmental regulator ABI3 with proteins identified from developing Arabidopsis seeds.

The ABI3 locus is a major regulator of embryo development in Arabidopsis and is essential for the simultaneous activation of the maturation pathway, as well as repression of germination and seedling development. We used a two-hybrid screen in yeast in order to identify proteins that interact with ABI3. Four ABI3-interacting proteins (AIPs) were identified which showed specific in vivo and in vitro interactions with the C-terminal region of ABI3 that contains the B2 and B3 domains, previously shown to have DNA binding activity. The expression characteristics of the genes encoding the AIPs have also been analysed in wild-type and abi3, lec1 and fus3 embryo mutants. This analysis demonstrated differential expression of these genes during normal embryo development and in the mutant lines. All the AIPs show homology to existing transcription factors and therefore they may function with ABI3 within the network of transcriptional regulators that control embryo development in Arabidopsis.

Amino Acid Sequence↗
PubMed2000

Morphological and metabolic changes in transgenic wheat with altered glycerol-3-phosphate acyltransferase or acyl-acyl carrier protein (ACP) thioesterase activities.

We have transformed varieties of wheat with a Pisum sativum glycerol-3-phosphate acyltransferase gene, and also with an Arabidopsis thaliana acyl-ACP thioesterase gene. Morphological (growth, organelle development) and metabolic changes (fatty acid labelling of chloroplast and non-chloroplast lipids) have been observed in transgenics with altered gene expression for either enzyme.

Arabidopsis↗
PubMed1998

Flight simulator evaluation of a novel flight instrument display to minimize the risks of spatial disorientation.

BACKGROUND: Spatial disorientation (SD) in flight remains a major source of attrition. Many SD accidents would occur regardless of the instrument display in use, since the aircrew are simply not looking at the instruments. However, there are a number of accidents which might be amenable to improved instrument displays. In an attempt to improve maintenance and reattainment of correct orientation with a reduced cognitive workload, a novel instrument display has been developed. This paper describes an assessment of the display in a UH-60 helicopter flight simulator. HYPOTHESIS: This study tested the hypothesis that during instrument flight and recovery from unusual attitudes, the novel display permits a more accurate maintenance and reestablishment of flight parameters than the standard flight instruments. METHODS: There were 16 male aviators who flew a simulated instrument flight profile and recovery from unusual attitudes using both the standard flight instruments and the novel display. The two display formats were tested both with and without a secondary task. RESULTS: When compared with the standard instruments, both control of flight parameters and recovery from unusual attitudes were significantly improved when using the novel display. Analysis of the secondary task scores showed that cognitive workload was reduced when using the novel display compared with the standard instruments. CONCLUSIONS: Results from all aspects of the assessment indicated benefits of the new display. Future testing should be carried out during real flight, and the display should be further developed to be used in a head-up or helmet-mounted device.

Adult↗
PubMed1998

The optokinetic cervico reflex during simulated helicopter flight.

INTRODUCTION: The optokinetic cervico reflex (OKCR) is a recently hypothesized, visually driven reflex that serves to stabilize the image of the external horizon on the retina during roll maneuvers in high-performance aircraft. Although reported anecdotally, head tilt during helicopter flight has not been studied formally. Such research is required to determine the full impact and significance that it may have on the flying performance of a rotary-wing aviator. OBJECTIVE: The aim of this study was to investigate the relationship between horizon position and the perception of orientation and, thus, to generate vital information to assess whether OKCR plays an important role in spatial disorientation. HYPOTHESIS: Pilots of rotary-wing aircraft will exhibit the OKCR. METHODS: A UH-60 flight simulator study, with 20 volunteer pilots participating, was performed to examine the effects of this reflex during day flight and during flight with night vision goggles (NVGs). RESULTS: The results confirm that the OKCR occurs during simulated helicopter flight, both with and without NVGs. As with previous studies, head roll increased during flight under visual meteorological conditions in relation to an increasing aircraft roll angle up to a maximum sustainable level and then remained constant. Head roll did not occur during flight under instrument meteorological conditions. CONCLUSION: The presence of the OKCR will impact rotary-wing operations. Various aspects are discussed, and recommendations are made for future research.

Adult↗
PubMed1997

Genotype and environment interact to control dormancy and differential expression of the VIVIPAROUS 1 homologue in embryos of Avena fatua.

Embryo dormancy is a reversible developmental state during which germination is repressed. In this study, inbred lines of Avena fatua were used to analyse the influence of genotype and environment on the dormant phenotype, and on expression of the homologue of the maize transcription factor VIVIPAROUS 1 (afVP 1). The cDNA for afVP 1 was cloned from mature embryos. Analysis of the predicted protein sequence revealed a high degree of similarity to other VP 1/ABI 3-related transcription factors, in particular in four regions previously shown to be highly conserved, including the BR2 region that has been shown to interact with several classes of sequence-specific DNA binding proteins. The potential of imbibed mature embryos for dormancy was analysed and shown to be determined primarily by genotype and secondarily by previous environmental experience of the mature seed acting on embryo genotype. Under all conditions studied, expression of afVP 1 and the A. fatua homologue of Em (shown in maize to be regulated by VP 1 during embryo maturation) were positively correlated with the dormant phenotype, whereas expression of A. fatua AMY-related RNAs was negatively correlated with dormancy (in barley AMY 6-4 has been shown to be repressed by VP 1). Expression of afVP 1 RNA was also shown in the dry seed to be positively correlated with the length of time required for seeds of the inbred lines to after-ripen. These results suggest new functions for the VP 1 transcription factor family in the control of dormancy-related processes in embryo cells of mature seeds, and the up-regulation of afVP 1 and afEm RNAs in the dormant state suggests that they are regulated by a switching mechanism in the mature seed that shows some aspects of reversibility.

Amino Acid Sequence↗
PubMed1995

Multiple modes of ligand recognition: crystal structures of cyclin-dependent protein kinase 2 in complex with ATP and two inhibitors, olomoucine and isopentenyladenine.

Cyclin-dependent kinases (CDKs) are conserved regulators of the eukaryotic cell cycle with different isoforms controlling specific phases of the cell cycle. Mitogenic or growth inhibitory signals are mediated, respectively, by activation or inhibition of CDKs which phosphorylate proteins associated with the cell cycle. The central role of CDKs in cell cycle regulation makes them a potential new target for inhibitory molecules with anti-proliferative and/or anti-neoplastic effects. We describe the crystal structures of the complexes of CDK2 with a weakly specific CDK inhibitor, N6-(delta 2-isopentenyl)adenine, and a strongly specific inhibitor, olomoucine. Both inhibitors are adenine derivatives and bind in the adenine binding pocket of CDK2, but in an unexpected and different orientation from the adenine of the authentic ligand ATP. The N6-benzyl substituent in olomoucine binds outside the conserved binding pocket and is most likely responsible for its specificity. The structural information from the CDK2-olomoucine complex will be useful in directing the search for the next generation inhibitors with improved properties.

Adenine↗
PubMed1995

Sustaining helicopter pilot performance with Dexedrine during periods of sleep deprivation.

BACKGROUND: Around-the-clock operations often are mandated in combat, but while aircraft can function effectively throughout continuous 24-hour periods, aviators often cannot because of sleep loss. An efficacious countermeasure in sustained operations may be the administration of dextroamphetamine (Dexedrine). HYPOTHESIS: Dexedrine will effectively prevent many of the performance problems associated with sleep deprivation in helicopter pilots. METHODS: A placebo-controlled, double blind study was conducted. Six U.S. Army helicopter pilots completed five flights in a UH-60 simulator while their performance was evaluated. Immediately following each flight, data were collected on electroencephalographic (EEG) activity and subjective mood ratings. Testing sessions occurred at 0100, 0500, 0900, 1300, and 1700. One hour prior to each of the first three flights on drug-administration days, the aviators were given 10 mg of Dexedrine or placebo. RESULTS: Dexedrine, in comparison to placebo, improved aviator simulator control on descents, straight-and-levels, standard-rate turns, and a left-descending turn. Performance was facilitated most noticeably at 0500, 0900, and 1700 (after 22, 26, and 34 hours of continuous wakefulness). EEG and mood data showed that alertness was sustained significantly by Dexedrine--there was reduced slow-wave EEG activity and improved rating of vigor and fatigue. No adverse behavioral or physiological effects were observed. CONCLUSIONS: Dexedrine appears to be effective for sustaining helicopter pilot performance during short periods of sleep loss without producing adverse side effects.

Adult↗
PubMed1994

The EPC approach to estimating safety from exposure to environmental chemicals.

Reference doses (RfDs) and reference concentrations (RfCs) developed by the United States Environmental Protection Agency (USEPA) are typically used in the quantitation of risk of potential adverse human health effects from exposure to environmental chemicals. For a large number of chemicals, however, USEPA RfDs and RfCs have not yet been determined. Thus, for risk assessments that involve a large number of chemicals, there is insufficient toxicity information with which to evaluate potential adverse human health effects for all chemicals present at a particular site. Due to this insufficiency, the risk assessor must either (1) ignore potential exposures on the assumption that omitting these exposures does not significantly alter decisions concerning the remediation of the site or (2) undertake a lengthy and costly analysis to generate the necessary RfDs or RfCs. A potential solution to this problem is to develop estimated permissible concentrations (EPCs), values which represent permissible environmental concentrations or related acceptable daily dosages derived from occupational exposure limits. In the present analysis, acceptable daily dosages determined using the EPC method were compared to USEPA RfDs or RfCs which were converted to dosages based on standard exposure assumptions. Based on a comparative analysis of EPCs and USEPA reference values for 103 chemicals, it was found that EPC daily dosages represent a reasonably conservative surrogate value when USEPA or state reference values are unavailable. Given that there are hundreds of chemicals with occupational exposure limits but no state or USEPA reference values, acceptance of the EPC methodology would provide an interim solution for the problem of insufficient toxicity information for a substantial number of environmental chemical contaminants.

Animals↗
PubMed1993

Crystal structure of cyclin-dependent kinase 2.

Cyclin-dependent kinase 2 (CDK2) is a member of a highly conserved family of protein kinases that regulate the eukaryotic cell cycle. The crystal structures of the human CDK2 apoenzyme and its Mg2+ ATP complex have been determined to 2.4 A resolution. The structure is bi-lobate, like that of the cyclic AMP-dependent protein kinase, but contains a unique helix-loop segment that interferes with ATP and protein substrate binding and probably plays a key part in the regulation of all cyclin-dependent kinases.

Adenosine Triphosphate↗
PubMed1993

Video microscopy of organelle inheritance and motility in budding yeast.

By adapting the time-lapse video microscopy techniques that were developed for larger, more complex cells, to living Saccharomyces cerevisiae cells, intracellular organelle movements were observed. Differential interference contrast optics revealed an organelle transport process in cells treated with mating pheromone. Small particles were observed to travel distances of up to 6 microns at rates of 0.11-0.17 (and in one case 0.80) micron/sec. Overall, the frequency of these motile events was quite low compared to what is observed in cell types traditionally studied by video microscopy. The ability to discern clearly the vacuole and nucleus in budding yeast revealed the dynamics of these organelles and the fact that their movements are carefully orchestrated during the cell cycle. Two types of vacuolar dynamics were observed: 1) interconversion between one large organelle and numerous smaller organelles and 2) the formation of projections that extend from the mother cell's vacuole into the bud. When applied to the study of the many available cytoskeletal and cell cycle mutants, the application of video microscopy to the study of organelle movements in living yeast cells will provide a unique opportunity to determine the molecular mechanisms of intracellular motility and to elucidate the temporal controls over these processes.

Biological Transport↗
PubMed1993

Actin structure and function: roles in mitochondrial organization and morphogenesis in budding yeast and identification of the phalloidin-binding site.

To further elucidate the functions of actin in budding yeast and to relate actin structure to specific roles and interactions in vivo, we determined the phenotypes caused by 13 charged-to-alanine mutations isolated previously in the single Saccharomyces cerevisiae actin gene. Defects in actin organization, morphogenesis, budding pattern, chitin deposition, septation, nuclear segregation, and mitochondrial organization were observed. In wild-type cells, mitochondria were found to be aligned along actin cables. Many of the amino acid substitutions that had the most severe effects on mitochondrial organization are located under the myosin "footprint" on the actin monomer, suggesting that actin-myosin interactions might underlie mitochondrial organization in yeast. In addition, one mutant (act1-129; R177A, D179A) produced an actin that assembled into cables and patches that could be visualized by anti-actin immunofluorescence in situ and that assembled into microfilaments of normal appearance in vitro as judged by electron microscopy but which could not be labeled by rhodamine-phalloidin in situ or in vitro. Rhodamine-phalloidin could label actin filaments assembled from all of the other mutant actins, including one (act1-119; R116A, E117A, K118A) that is altered at a residue (E117) that can be chemically cross-linked to phalloidin. The implication of residues R177 and/or D179 in phalloidin binding is in close agreement with a recently reported molecular model in which the phalloidin-binding site is proposed to be at the junction of two or three actin monomers in the filament.

Actin Cytoskeleton↗
PubMed1992

Assessment of the drug interaction between intravenous nitroglycerin and heparin.

OBJECTIVE: To assess whether a clinically significant interaction occurs between heparin and nitroglycerin (NTG). METHODOLOGY: Activated partial thromboplastin time (APTT) was measured in patients with unstable angina who were stabilized on intravenous NTG and heparin just prior to weaning the NTG infusion, and one and four hours after stopping the NTG. RESULTS: In 22 heparin-treated patients (20 men, 2 women; aged 56.7 +/- 10 years; weight 79.5 +/- 15 kg), the APTT ratio was inversely related to the dose of NTG (slope = -0.003; p < 0.05). However, there were no significant differences between the APTT values measured before and after discontinuation of NTG (p = 0.8511). CONCLUSIONS: Our study demonstrates a clinically insignificant interaction between NTG and heparin at NTG doses commonly used in patients.

Aged↗