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D Price

Publications and source records attributed to D Price.

At least 37 records · Page 2Linked to original sources
PubMed1998

Keratin modifications and solubility properties in epithelial cells and in vitro.

The gains that have been made in characterizing some of the keratin posttranslational modifications have helped answer some questions regarding these modifications and have generated an information base for asking additional refined questions in future studies. Highlights of where we believe we currently stand with regard to keratin posttranslational modifications are as follows: 1. Keratin glycosylation, via O-GlcNAc, is a dynamic modification that has been conclusively identified in K13, K8, and K18. Three serine glycosylation sites in the head domain of K18 have been identified, and it is possible that all keratins are glycosylated. The function of this modification remains to be defined, but is likely to be different from phosphorylation, since the two modifications are generally segregated on different molecules and several examples exist whereby both modifications increase simultaneously. 2. Keratin phosphorylation occurs within the tail and/or head domains of all keratins that have been examined. Several serine phosphorylation sites and some of the relevant kinases have been characterized in K8, K6, and K18, and serine/threonine sites have been identified in K1. Functions of keratin phosphorylation that have significant experimental support include a role in filament solubility and reorganization and a role in regulating keratin binding with other cytoplasmic proteins. The significance of filament reorganization and increased solubility under a variety of physiologic conditions such as mitosis and cell stress are important areas of future and ongoing investigation. Other associations with keratin phosphorylation include protection against cell stress, cell signaling, apoptosis, and cell compartment-specific roles. At this stage, however, it is not known if these associations play direct or indirect roles. 3. Keratin transglutamination occurs in epidermal and simple epithelial keratins under physiologic and pathologic states, respectively. In the physiological context, the role of this modification is clear in terms of providing a compact protective structure, while in the pathologic context of liver disease the role remains ambiguous. 4. Proteolysis of K18 and K19 by caspases occurs during apoptosis, and generates stable keratin fragments that are highly enriched within the cytoskeletal compartment. Proteolysis of the type II keratins appears to be spared for reasons that remain to be defined. It is likely that this apoptosis-associated degradation involves all type I keratins. Keratin fragments are also noted in sera of patients in association with a variety of epithelial tumors. If a signal does exist for the apoptosis-associated fragmentation, aside from caspase activation, then it appears that the overall increase in keratin phosphorylation during apoptosis does not account for this signal. 5. Keratins undergo several other posttranslational modifications including disulfide bond formation (not found in K8/18 due to lack of cystienes) and acetylation of their N-terminal serines. Modification by lipids is also possible, but this modification requires further confirmation. 6. Keratin solublility is highly dynamic and varies profoundly depending on the keratin pair and the physiologic state of the cell. Within the keratin family, simple epithelial keratins are among the most soluble (approximately 5% of K8/18 is soluble at basal conditions). Phosphorylation plays an important role in modulating keratin solubility, and distinct differences occur in site-specific phosphorylation depending on the soluble versus cytoskeletal partitioning of the keratin. Keratin solubility (at least for K8/18) also appears to be regulated by 14-3-3 proteins via K18 Ser33 phosphorylation.

Acetylation↗
PubMed1997

Drosophila factor 2, an RNA polymerase II transcript release factor, has DNA-dependent ATPase activity.

Drosophila factor 2 has been identified as a component of negative transcription elongation factor (N-TEF) that causes the release of RNA polymerase II transcripts in an ATP-dependent manner (Xie, Z. and Price D. H. (1996) J. Biol. Chem. 271, 11043-11046). We show here that the transcript release activity of factor 2 requires ATP or dATP and that adenosine 5'-O-(thiotriphosphate) (ATPgammaS), adenosine 5'-(beta,gamma-imino)triphosphate (AMP-PNP), or other NTPs do not support the activity. Factor 2 demonstrated a strong DNA-dependent ATPase activity that correlated with its transcript release activity. At 20 microg/ml DNA, the ATPase activity of factor 2 had an apparent Km(ATP) of 28 microM and an estimated Kcat of 140 min-1. Factor 2 caused the release of nascent transcripts associated with elongation complexes generated by RNA polymerase II on a dC-tailed template. Therefore, no other protein cofactors are required for the transcript release activity of factor 2. Using the dC-tailed template assay, it was found that renaturation of the template was required for factor 2 function.

Adenosine Triphosphatases↗
PubMed1997

Association of glucose-regulated protein (grp78) with human keratin 8.

Keratin polypeptides 8 and 18 (K8/18) are intermediate filament proteins that are expressed in 'simple-type' epithelial cells. They associate with several proteins including the 70 kDa cytoplasmic heat shock proteins (hsp70). We identified the human 78 kDa glucose-regulated protein (grp78) as a keratin-associated protein. Keratin-grp78 association was noted after co-immunoprecipitation of K8/18 from HT29 detergent solubilized cell lysates, and appears to involve non-posttranslationally modified grp78. The grp78-K8/18 association is induced by culturing cells in the presence of tunicamycin or after glucose starvation. K8/18-bound grp78 can be dissociated by Mg-ATP and the association can be reconstituted in vitro using purified grp78, then redissociated again by Mg-ATP. Binding of grp78 occurs preferentially with K8, and when reconstituted does not depend on the posttranslational modification state of K8/18. Co-incubation of K8/18 with hsp70 and grp78 shows preferential association with hsp70. Our results demonstrate a direct association of grp78 with K8 under conditions that induce grp78 expression.

Adenosine Triphosphate↗
PubMed1997

P-TEFb kinase is required for HIV Tat transcriptional activation in vivo and in vitro.

To identify novel inhibitors of transcriptional activation by the HIV Tat protein, we used a combination of in vitro and in vivo Tat-dependent transcription assays to screen >100,000 compounds. All compounds identified blocked Tat-dependent stimulation of transcriptional elongation. Analysis of a panel of structurally diverse inhibitors indicated that their target is the human homolog of Drosophila positive transcription elongation factor b (P-TEFb). Loss of Tat transactivation in extracts depleted of the kinase subunit of human P-TEFb, PITALRE, was reversed by addition of partially purified human P-TEFb. Transfection experiments with wild-type or kinase knockout PITALRE demonstrated that P-TEFb is required for Tat function. Our results suggest that P-TEFb represents an attractive target for the development of novel HIV therapeutics.

Animals↗
PubMed1997

Effect of variation in seat tube angle at different seat heights on submaximal cycling performance in man.

The effect of seat tube angle at selected seat heights (96, 100 and 104% trochanteric height) on heart rate, VO2 and lower limb kinematics was evaluated in 14 competitive male road racing cyclists during discontinuous submaximal exercise (200 W) on an air-resistance ergometer at seat tube angles of 68, 74 and 80 degrees. The tests were randomized to complete the nine combinations (three seat heights, three tube angles) in opposite directions from a starting tube angle of 74 degrees and 100% trochanteric height to avoid any time or sequence bias. Power efficiency was calculated for each combination from work done and VO2. All results were analysed using ANOVA for repeated measures. At a seat tube angle of 80 degrees, mean VO2 was significantly lower and power efficiency significantly higher compared with an angle of 74 degrees at all three seat heights, while heart rate was significantly lower only at a seat height equal to trochanteric height. At a seat tube angle of 74 degrees, mean VO2 and heart rate were significantly lower and power efficiency significantly higher compared with an angle of 68 degrees at all three seat heights. Hip range of movement and maximum and minimum hip angle were significantly less at an angle of 80 degrees compared with 68 degrees. Further biomechanical analysis suggested that the improvement in cycling efficiency observed at steeper seat tube angles was produced in part by the resultant altered ankling pattern of the cyclist.

Adult↗
PubMed1997

Co-evolution of human immunodeficiency virus and cytotoxic T-lymphocyte responses.

After more than a decade of intensive research, the precise role of human immunodeficiency virus (HIV)-specific cytotoxic T lymphocytes (CTL) in determining the course of the infection remains open to argument. It is established that HIV-specific CTL appear early in the infection and are temporally associated with the clearance of culturable virus from the blood; that CTL are generally detectable at very high levels throughout the asymptomatic phase and decline at the time of progression to AIDS; and that CTL-mediated killing is sufficiently fast to prevent production of new virions by HIV-infected cells. However, viral turnover is high throughout the course of the infection, and infected individuals progress inexorably to disease in spite of the CTL response. In order to address the question of whether CTL play an active part in influencing the course of HIV infection, one approach has been to seek evidence for CTL-mediated selection pressure on the virus. Several clear examples of CTL epitope-specific mutations selected to fixation are described. We argue that CTL escape is a common event which occurs at all stages of the infection. Detailed longitudinal studies are required to detect CTL escape and to understand the complexities contributed by factors such as a polyvalent CTL response and the presence of epitope variants which antagonise the CTL response. In conclusion, there is strong evidence of a dynamic process in which CTL impose important selection constraints upon HIV from which the virus attempts to escape; ultimately, at the time of disease progression, the tenuous control of CTL over the virus is lost.

Animals↗
PubMed1996

Selective effects of nerve growth factor on spatial recent memory as assessed by a delayed nonmatching-to-position task in the water maze.

Nerve growth factor (NGF) ameliorates age-related deficits in certain types of memory in rats. Although the effects of NGF on reference memory are well documented, the influence of NGF on recent memory is less well understood. The issue of recent memory is of primary importance in the design of therapies for cognitive disorders, because this type of memory is impaired in elderly humans and is severely affected early in the course of Alzheimer's disease (AD). The present study was designed to evaluate the efforts of NGF on recent memory in a task that used escape from water as the motivating stimulus and used the same design as forced-choice recognition tasks given to humans. Fischer-344 rats, 4 months old (4MO) or 23 months old (23MO), were pretested in a new spatial recent memory task designed for the Morris water maze, a delayed nonmatching-to-position task, and infused intraventricularly with recombinant human NGF or vehicle. After 2 weeks of NGF infusion, no substantial changes in behavior were observed in either age group. However, NGF treatment extended over 4 weeks improved considerably the choice accuracy of 23MO rats to a level similar to the performance of 4MO rats. These results, together with our previous work (Markowska et al., 1994), indicate that the effects of NGF on spatial recent memory are more intense than on spatial reference memory. NGF suppressed the body weight gain in 4MO rats but did not affect 23MO rats. In 23MO rats, NGF mildly counteracted age-related deficits in inhibitory avoidance, but did not have an effect in young rats.

Aging↗
PubMed1996

Lessons for health care rationing from the case of child B.

More details have emerged about the child B leukaemia case with the publication of the All England Law Report on the Appeal Court decision. At the time the view was widely held that the controversy might have been avoided if the responsible health authority had consulted the public. The law report reveals, however, that the courts adopted a moral language widely at variance with that of the patient's doctor. The courts were concerned to support a utilitarian decision procedure based on calculations of the greatest overall good; the doctor was concerned with the best interests of a sick child. The doctor-patient relationship may be damaged when public consideration transforms the issue in this way. Also, the Appeal Court supported a decision which claimed to have "weighed" opposing evaluations, but it excused the health authority from describing how that weighing took place. One of the main criticisms of the utilitarian approach, however, is that weighing of this type is extremely difficult to justify. By its ruling the court has made legal challenge on the grounds of inadequate consultation virtually impossible to substantiate.

Child↗
PubMed1996

Radiological features of a symptomatic splenic hamartoma.

Symptomatic splenic hamartomas are rare in the pediatric age group, with only four previous reports in the literature. Splenic hamartoma has been reported as a solid homogeneous mass without calcification on CT and ultrasound (US), and only one previous report of the findings on MRI has been published. We report a case of a large symptomatic splenic hamartoma in a 14-year-old girl who presented with splenomegaly, pancytopenia and growth retardation. A solid mass with multiple punctate foci resembling calcifications was seen on US. The mass was heterogeneous and better demarcated on enhanced CT. Radiocolloid scintigraphy demonstrated uptake within the lesion, but less than that of normal spleen. The mass was isointense relative to normal splenic tissue on T1-weighted MRI (0.5 T) and of increased intensity with T2 weighting. At splenectomy, a red pulp hamartoma was identified, which contained nodules of hyalinization and necrosis thought to account for the punctate foci seen on US.

Adolescent↗
PubMed1996

MR of the pituitary in patients with Prader-Willi syndrome: size determination and imaging findings.

Prader-Willi syndrome (PWS) is an unusual genetic disorder characterized by short stature, obesity, hypogonadism, hypotonia, cognitive impairment, and dysmorphic facies. There is an interstitial deletion of the proximal long arm of chromosome 15 in about 70 % of patients. Some of these clinical features suggest a central hypothalamic/pituitary dysfunction, and recent investigations have demonstrated a marked impairment in spontaneous growth hormone (GH) secretion. We studied 15 GH-deficient PWS patients by magnetic resonance imaging (MRI) to determine whether there was a diminution in the gross morphological size of the anterior pituitary gland, the site of GH synthesis. We also set out to catalog the pertinent imaging findings in this patient population. Our results indicate that this is the first report documenting pituitary size by MRI in PWS patients. No statistically significant difference was found in the height of the anterior pituitary gland in PWS patients compared with either normal children or children with isolated GH deficiency. An interesting imaging finding is that three of 15 patients (20 %) demonstrated complete absence of the posterior pituitary bright spot (PPBS), and a fourth patient demonstrated a small PPBS. These observations reflect an objective physiologic disturbance in the hypothalamus. The clinical and radiologic implications of these findings are discussed.

Adolescent↗
PubMed1996

Oligomers in plastics packaging. Part 1: Migration tests for vinyl chloride tetramer.

Vinyl chloride (VC) tetramer has been studied as a representative oligomer that has the potential for migration from plastics packaging. Poly(vinyl chloride) (PVC) bottles for retail beverages were analysed by a process of dissolution followed by gas chromatography. Tetramer levels ranged from 70 to 190 mg/kg in the plastic. When these bottles were tested for migration into the simulants distilled water, 3% acetic acid, 15% ethanol and olive oil, no tetramer migration was detected at a limit of 5-10 micrograms/kg. Since, of the low molecular weight oligomers, the tetramer had the highest concentration in the PVC plastics, it is concluded that the other VC oligomers of higher molecular weight, would not migrate above this limit of detection either.

Acetates↗
PubMed1996

Ruralising the undergraduate medical curriculum through consultation with key stake holders.

This paper describes the approach taken at the University of Queensland to broaden the scope of curriculum design to involve rural general practitioners, medical students and rural health care consumers. A form of nominal group process in serial telephone teleconferences was used, with a group of rural general practitioners, to develop and pilot curriculum content, learning strategies and assessment methods. Medical students assisted in the evaluation of the curriculum and representatives of rural organisations were consulted about the value of hosting medical students in rural communities. The three groups made significant contributions to the project. The results will be trialed for the entire year 6 cohort (240 students) in 1995 and will form the basis of the planned rural practice term in the new graduate course.

Community Participation↗
PubMed1996

Collaboration in curriculum design: preparing educational programs for Australian rural medical practitioners.

Details of the process used by the authors, as curriculum design consultants, for the Rural Medicine Curriculum Design Project are presented. The process resulted in separate curricula in surgery, anaesthesia and obstetrics for use in advanced training within the Rural Training Program of the Faculty of Rural Medicine of the Royal Australian College of General Practitioners (RACGP). Key features of the design process are synthesised as a guide to projects where agreement across divergent groups is essential.

Anesthesiology↗