Search PubMed⌕ Search

Biomedical subjects

M A White

Publications and source records attributed to M A White.

At least 19 recordsLinked to original sources
PubMed2001

Raf-induced transformation requires an interleukin 1 autocrine loop.

The c-Raf-1 serine/threonine protein kinase plays a critical role in the proliferation of most cell types that have been examined. As such, the Raf proto-oncogene is thought to play a central role in the development of human tumors. Although the c-raf-1 gene itself rarely appears to be mutated in human tumors, the kinase activity of Raf is frequently found to be more active in tumor cells, likely through constitutive activation of upstream activators of Raf. The downstream events triggered by Raf that are involved in transformation have been studied less extensively. We show in this study that Raf-induced transformation of NIH 3T3 cells requires the activation of the ubiquitously expressed transcription factor, nuclear factor-kappaB, by Raf. Furthermore, through the use of CrmA, interleukin 1 (IL-1) receptor antagonist, and a dominant-negative form of TRAF6, we demonstrate a requirement for IL-1 production and signaling from the IL-1 receptor as necessary components of Raf-induced transformation. These results indicate that IL-1 may be used as an autocrine growth factor by a number of tumors in which activation of Raf plays an important role in transformation and suggest that blockade of IL-1 signaling may be an approach to limiting the growth of certain tumors.

3T3 Cells↗
PubMed2000

ERK5 and ERK2 cooperate to regulate NF-kappaB and cell transformation.

We have previously demonstrated an involvement of MEK5 and ERK5 in RafBXB-stimulated focus formation in NIH3T3 cells. We find here that MEK5 and ERK5 cooperate with the RafBXB effectors MEK1/2 and ERK1/2 to induce foci. To further understand MEK5-ERK5-dependent signaling, we examined potential MEK5-ERK5 effectors that might influence focus-forming activity. Consistent with results from our focus-formation assays, constitutively active variants of MEK5 and MEK1 synergize to activate NF-kappaB, and MEK5 and ERK5 are required for activation of NF-kappaB by RafBXB. The MEK5-ERK5 pathway is also sufficient to activate both NF-kappaB and p90 ribosomal S6 kinase. Our results support the hypothesis that NF-kappaB and p90 ribosomal S6 kinase are involved in MEK5-ERK5-dependent focus formation and may serve as integration points for ERK5 and ERK1/2 signaling.

3T3 Cells↗
PubMed2000

Uncoupling Raf1 from MEK1/2 impairs only a subset of cellular responses to Raf activation.

The Raf family of serine/threonine protein kinases is intimately involved in the transmission of cell regulatory signals controlling proliferation and differentiation. The best characterized Raf substrates are MEK1 and MEK2. The activation of MEK1/2 by Raf is required to mediate many of the cellular responses to Raf activation, suggesting that MEK1/2 are the dominant Raf effector proteins. However, accumulating evidence suggests that there are additional Raf substrates and that subsets of Raf-induced regulatory events are mediated independently of Raf activation of MEK1/2. To examine the possibility that there is bifurcation at the level of Raf in activation of MEK1/2-dependent and MEK1/2-independent cell regulatory events, we engineered a kinase-active Raf1 variant (RafBXB(T481A)) with an amino acid substitution that disrupts MEK1 binding. We find that disruption of MEK1/2 association uncouples Raf from activation of ERK1/2, induction of serum-response element-dependent gene expression, and induction of growth and morphological transformation. However, activation of NF-kappaB-dependent gene expression and induction of neurite differentiation were unimpaired. In addition, Raf-dependent activation of p90 ribosomal S6 kinase was only slightly impaired. These results support the hypothesis that Raf kinases utilize multiple downstream effectors to regulate distinct cellular activities.

3T3 Cells↗
PubMed2000

A randomised crossover trial of chemotherapy in the home: patient preferences and cost analysis.

OBJECTIVES: To determine patient preferences and cost differences between home-based and hospital-based chemotherapy. DESIGN: Randomised crossover trial. SETTING: A tertiary cancer hospital in Melbourne, Victoria. PARTICIPANTS: 20 patients who required chemotherapy suitable for administration at home. INTERVENTIONS: Patients were assigned at random to receive their first chemotherapy treatment in either the home or the hospital and the second treatment in the alternative setting. MAIN OUTCOME MEASURES: Patient preference, costs. RESULTS: There was universal agreement by the 20 patients in the randomised trial that home-based chemotherapy was the preferred option (P < 0.0001). No problems were nominated by the patients as being associated with home-based chemotherapy. Home-based treatment was estimated to result in an increased cost of $83 (P = 0.0002) for each chemotherapy treatment compared with hospital-based treatment. Reported advantages for chemotherapy in the home included the elimination of travel, reduction in treatment-associated anxiety, reduction in the burden on carers and family, and the ability to continue other duties. There were no significant complications associated with administration of chemotherapy in the home. CONCLUSIONS: Patients prefer home-based chemotherapy to hospital-based treatment. The future of chemotherapy-in-the-home programs in Australia will depend on whether patient preferences are deemed to offset any potential increase in costs.

Aged↗
PubMed2000

Recovery from stroke: does rehabilitation counselling have a role to play?

AIMS AND OBJECTIVES: The aim of this paper is to explore the stroke literature, with particular emphasis on the management of psycho-social issues during and in the aftermath of stroke rehabilitation. Within the literature, there are a number of studies that indicate that the present 'medical/physical' approach to stroke rehabilitation may not be achieving desirable long-term psycho-social outcomes and these are considered. The studies highlight the potential effect of the human emotional and social aspects of having a stroke upon the physical and mental well-being of the person. For the person living with stroke, the ability to maintain a positive sense of direction in life as well as hold onto their, or develop a new, identity is crucial in terms of adapting to change. Holding onto one's self-worth and unity with the past and anticipating the future enhances the ability to cope and adapt in the aftermath of stroke rehabilitation. This links with the investigation into rehabilitation counselling as a potential strategy for the management of long-term psycho-social functional status following stroke. CONCLUSION: It is suggested that the medical model of stroke rehabilitation places undue emphasis on clinical diagnosis and treatment. By default, measurement of physical independence or disability that is compressed into standardized scales has arguably led to the neglect of the emotional and social consequences of stroke and a partial or inhibited view of the person. It is proposed that there is a need to develop and evaluate the effectiveness of rehabilitation counselling from short-term stroke rehabilitation through to long-term psychosocial adaptation, for this client group to provide clear evidence for service provision.

Counseling↗
PubMed2000

The prevalence of alcohol, cannabinoids, benzodiazepines and stimulants amongst injured drivers and their role in driver culpability: part ii: the relationship between drug prevalence and drug concentration, and driver culpability.

Blood samples from 2,500 injured drivers were analysed for alcohol, cannabinoids (measured by the presence of THC), benzodiazepines and stimulants. The relationship between the prevalence and concentration of drugs and the culpability of the driver was examined using an objective method for assessing culpability. There were no significant differences between males and females with respect to culpability. However, there was a relationship between age and culpability: drivers under 26 years and over 60 years were more likely to be culpable. Drivers who tested positive for alcohol only, benzodiazepines only and the combinations of alcohol and THC and alcohol and benzodiazepines were significantly more likely to be culpable for the crash compared with the drug-free group. Conversely, a lower percentage of drivers who only tested positive for THC were culpable for the crash compared with drug-free drivers. This difference was not statistically significant. For car drivers in single-vehicle crashes, the majority of drivers were judged culpable irrespective of drug use. In multiple-vehicle crashes, car drivers testing positive for alcohol only or benzodiazepines only were more likely to be culpable for the crash compared with drug-free drivers. For motorcycle riders in both single- and multiple-vehicle crashes, there were no significant differences between the drug-positive and drug-free groups. A higher percentage of drug-free riders in multiple-vehicle crashes were culpable compared with riders who only tested positive for THC, but this difference was not statistically significant. There was a significant concentration-dependent relationship between alcohol and culpability: as blood alcohol concentration increased, so did the percentage of culpable drivers. When THC was used alone, there was no significant increase in culpability. For those drivers with benzodiazepines at therapeutic concentrations and above, there was a significant increase in culpability. The relationship between stimulants and culpability was not significant, although a higher proportion of stimulant-positive drivers were culpable compared with drug-free drivers. The combinations of alcohol and THC, and alcohol and benzodiazepines also produced a significant increase in culpability, but this increase was not significantly greater than that produced by alcohol alone.

Accidents, Traffic↗
PubMed2000

The prevalence of alcohol, cannabinoids, benzodiazepines and stimulants amongst injured drivers and their role in driver culpability: part i: the prevalence of drug use in drive the drug-positive group.

Blood samples from 2,500 injured drivers were analysed for alcohol, cannabinnoids, benzodiazepines and stimulants. Overall, three-quarters of drivers tested negative for drugs. Alcohol was the most frequently detected drug. Cannabinoids were also detected at high rates, but the majority of drivers tested positive for THC-acid, the inactive metabolite of THC. Benzodiazepines and stimulants were detected at low rates, and detection rates for combinations of drugs were also low. Males were more likely to test positive for drugs, especially alcohol and THC, whereas females were more likely to test positive for benzodiazepines. A similar proportion of car drivers and motorcycle riders tested positive for drugs, although riders were more likely to test positive for THC. Single-vehicle crashes were particularly associated with alcohol for both car driver and riders, and for riders, multiple-vehicle crashes were particularly associated with THC.

Accidents, Traffic↗
PubMed2000

Body image assessment for obesity (BIA-O): development of a new procedure.

OBJECTIVE: A new measure of body image, named the body image assessment for obesity (BIA-O) was developed and tested for reliability and validity in a sample of 1,209 adult men and women. Separate BIA-O procedures were developed for men and women. Current, ideal and reasonable body image estimates of Caucasian and African-American men and women were compared. METHOD: Figural stimuli of males and females were developed for body sizes ranging from very thin to very obese in 18 increments. Participants selected figures that represented estimates of current, ideal and reasonable (a body size that could be maintained over time) body size. Some participants (n=641) also completed two measures of body dissatisfaction in a test of the validity of the BIA-O as a measure of body dissatisfaction. A sample of 77 participants was administered the BIA-O on two occasions to test the test-retest reliability of the BIA-O. RESULTS: The reliability of the BIA-O was supported by test-retest reliability coefficients which ranged from 0.65 to 0.93. Concurrent validity of the discrepancy between current and ideal and current and reasonable body size estimates was supported by positive correlations with two measures of body dissatisfaction. The BIA-O body size estimates of Caucasians and African-Americans, controlled for age and BMI, were compared. As BMI increased, Caucasian men and women were found to select larger current body size estimates in comparison to African-Americans. DISCUSSION: The reliability and validity of the BIA-O were supported. Greater body size dissatisfaction in obese Caucasians, relative to African-Americans of the same size, may be a function of biased estimates of current body size.

Adolescent↗
PubMed2000

Family dynamics, parental-fetal attachment and infant temperament.

Family dynamics, parental-fetal attachment and infant temperament The purpose of this longitudinal study of families having their first or second baby was to explore relationships among family dynamics, paternal- and maternal-fetal attachment, and infant temperament. Data were collected from 156 women and 62 of their partners during the third trimester of pregnancy. One year later, when the infant was 8-9 months old, 75 of the women and 30 of their partners participated. In a hierarchical multiple regression analysis, after controlling for demographic variables, mutuality in the family was associated with greater maternal- and paternal-fetal attachment. Family dynamics were stable across the transition to parenthood except for an increase in role conflict reported by mothers. Sensitivity to specific family experiences by clinicians can provide assistance to families during these periods.

Adult↗
PubMed2000

Ral GTPases contribute to regulation of cyclin D1 through activation of NF-kappaB.

Ral GTPases have been implicated as mediators of Ras-induced signal transduction from observations that Ral-specific guanine nucleotide exchange factors associate with Ras and are activated by Ras. The cellular role of Ral family proteins is unclear, as is the contribution that Ral may make to Ras-dependent signaling. Here we show that expression of activated Ral in quiescent rodent fibroblasts is sufficient to induce activation of NF-kappaB-dependent gene expression and cyclin D1 transcription, two key convergence points for mitogenic and survival signaling. The regulation of cyclin D1 transcription by Ral is dependent on NF-kappaB activation and is mediated through an NF-kappaB binding site in the cyclin D1 promoter. Ral activation of these responses is likely through an as yet uncharacterized effector pathway, as we find activation of NF-kappaB and the cyclin D1 promoter by Ral is independent of association of Ral with active phospholipase D1 or Ral-binding protein 1, two proteins proposed to mediate Ral function in cells.

3T3 Cells↗
PubMed1999

Contribution of the ERK5/MEK5 pathway to Ras/Raf signaling and growth control.

The activity of the catalytic domain of the orphan MAP kinase ERK5 is increased by Ras but not Raf-1 in cells, which suggests that ERK5 might mediate Raf-independent signaling by Ras. We found that Raf-1 does contribute to Ras activation of ERK5 but in a manner that does not correlate with Raf-1 catalytic activity. A clue to the mechanism of action of Raf-1 on ERK5 comes from the observation that endogenous Raf-1 binds to endogenous ERK5, suggesting the involvement of regulatory protein-protein interactions. This interaction is specific because Raf-1 binds only to ERK5 and not ERK2 or SAPK. Finally, we demonstrate the ERK5/MEK5 pathway is required for Raf-dependent cellular transformation and that a constitutively active form of MEK5, MEK5DD, synergizes with Raf to transform NIH 3T3 cells. These observations suggest that ERK5 plays a large role in Raf-1-mediated signal transduction.

Animals↗
PubMed1999

Functional requirement of p23 and Hsp90 in telomerase complexes.

Most normal human diploid cells have no detectable telomerase; however, expression of the catalytic subunit of telomerase is sufficient to induce telomerase activity and, in many cases, will bypass normal senescence. We and others have previously demonstrated in vitro assembly of active telomerase by combining the purified RNA component with the reverse transcriptase catalytic component synthesized in rabbit reticulocyte extract. Here we show that assembly of active telomerase from in vitro-synthesized components requires the contribution of proteins present in reticulocyte extracts. We have identified the molecular chaperones p23 and Hsp90 as proteins that bind to the catalytic subunit of telomerase. Blockade of this interaction inhibits assembly of active telomerase in vitro. Also, a significant fraction of active telomerase from cell extracts is associated with p23 and Hsp90. Consistent with in vitro results, inhibition of Hsp90 function in cells blocks assembly of active telomerase. To our knowledge, p23 and Hsp90 are the first telomerase-associated proteins demonstrated to contribute to telomerase activity.

Adenosine Triphosphate↗
PubMed1999

Determination of trace elements in porcine brain by inductively coupled plasma-mass spectrometry, electrothermal atomic absorption spectrometry, and instrumental neutron activation analysis.

Methods have been developed for the analyses of trace metals in various areas of porcine brains, (temporal, parietal, frontal cortex, both right and left hemispheres). Determinations were carried out using inductively coupled plasma-mass spectrometry (ICP-MS) and electrothermal atomic absorption spectrometry (ETAAS). The elements investigated were Li, Mn, Cu, Zn, Cd, Hg, and Pb by ICP-MS and Cu, Cd, and Mn by ETAAS. For determination by ICP-MS, a method of standard additions calibration coupled with internal standards was used, and for ETAAS, standard additions calibrations were prepared. The accuracy of all methods was determined using NIST and IAEA certified reference material. A small number of pig brains were analyzed by instrumental neutron activation analysis for Cr, Co, Cs, Fe, Rb, Se, Sc, Sb, and Zn using the comparator method of analysis. Four separate NIST standard reference materials have been used to examine the validity of the comparator method.

Animals↗
PubMed1999

A comparison of inductively coupled plasma mass spectrometry with electrothermal atomic absorption spectrophotometry for the determination of trace elements in blood and urine from non occupationally exposed populations.

Quadrupole Inductively coupled plasma mass spectrometric (QICP-MS) and electrothermal atomic absorption spectrophotometric (ETAAS) methods for the determination of Pb and Cd in whole blood and Al, Cd, Co and Ni in urine were compared. Simple sample pretreatments were used for both instrumental techniques. Urine samples were diluted with either Millipore water or dilute HNO3, while blood samples were diluted with a solution containing either 0.14M NH3 or 0.03 M NH3, 0.05% EDTA and 0.05% Triton X-100 in Millipore water. Scandium, yttrium and indium were used as internal standards for ICP-MS measurements and (NH4)2HPO4 as a chemical modifier for the determination of Pb and Cd by ETAAS. For ICP-MS analysis, pneumatic nebulization was used for introduction of urine samples and flow injection for introduction of blood samples. Matrix matched standards were used for all calibrations and methods were validated by analyzing reference materials and samples from external quality assurance programmes. Concentrations of the listed metals were determined in blood and urine samples obtained from a healthy non occupationally exposed population and reference samples, using both instrumental techniques. The study group (n = 90) was randomly selected from a study population (n = 220) recruited from three regions considered representative of the environment encountered by the majority of the United Kingdom population. Males and females were equally represented and ranged in age from 17-65 yrs. The correlation between results obtained by the two techniques was good for all elements measured, ranging from r = 0.88 for Co in urine to r = 0.99 for both Pb and Cd in blood.

Adolescent↗
PubMed1999

Absence of cancer-associated changes in human fibroblasts immortalized with telomerase.

The ectopic expression of telomerase in normal human cells results in an extended lifespan, indicating that telomere shortening regulates the timing of cellular senescence. As telomerase expression is a hallmark of cancer, we investigated the long-term effects of forced expression of human telomerase catalytic component (hTERT) in normal human fibroblasts. In vitro growth requirements, cell-cycle checkpoints and karyotypic stability in telomerase-expressing cells are similar to those of untransfected controls. In addition, co-expression of telomerase, the viral oncoproteins HPV16 E6/E7 (which inactivate p53 and pRB) and oncogenic HRAS does not result in growth in soft agar. Thus, although ectopic expression of telomerase in human fibroblasts is sufficient for immortalization, it does not result in changes typically associated with malignant transformation.

Catalytic Domain↗
PubMed1999

Cancer patients' expectations of the role of family physicians in communication about complementary therapies.

OBJECTIVE: To explore cancer patients' experiences with and expectations of the role of family physicians in communication about complementary therapies. DESIGN: Focus group interviews. SETTING: British Columbia Cancer Agency and the University of Calgary. PARTICIPANTS: Sample of 14 cancer patients using complementary therapies comprising 3 focus groups (2 in BC and 1 in Alberta). RESULTS: The role of family physicians in discussing complementary therapies varied from being extraneous to patients' decision making to being a partner in making decisions about cancer treatments. Patients expected their physicians to be supportive, caring, kind and to show an interest in them. They also expected their physicians to be accepting and nonjudgmental regarding complementary therapy use and to reinforce a sense of hope. Most patients did not expect their doctors to have extensive knowledge about these therapies. All patients strongly felt the need to seek information themselves. In addition, they felt that believing in the type of therapies they were using was very important. CONCLUSION: Family physicians can play an important role in exploring and discussing complementary therapies with their patients. It is important that they are made aware of their patients' needs in this area.

Aged↗
PubMed1998

Differential effects of PAK1-activating mutations reveal activity-dependent and -independent effects on cytoskeletal regulation.

PAKs are serine/threonine protein kinases that are activated by binding to Rac or Cdc42hs. Different forms of activated PAK1 have been reported to either promote membrane ruffling and focal adhesion assembly or cause focal adhesion disassembly and stress fiber dissolution. To understand the basis for these distinct morphological effects, we have examined the mechanism of mutational activation of PAK1, and characterized the effects of different active PAK1 proteins on cytoskeletal structure in vivo. We find that PAK1 contains an autoinhibitory domain that overlaps with its small G protein binding domain and that two separate activating mutations within this regulatory region each decrease autoinhibitory activity. Because only one of these mutations affects Cdc42hs binding activity, this indicates that activation of PAK1 by these mutations results from interference with the function of the autoinhibitory domain and not with small G protein binding activity. When we examined the morphological effects of these different forms of PAK1 in vivo, we found that PAK1 kinase activity was associated with disassembly of focal adhesions and actin stress fibers and that this may require interaction with potential SH3 domain-containing proteins. Lamellipodia formation and membrane ruffling caused by active PAK1 expression, however, was independent of PAK1 catalytic activity and likely requires interaction among multiple proteins binding to the PAK1 regulatory domain.

Cell Adhesion↗