Biomedical subjects
P Lloyd
Publications and source records attributed to P Lloyd.
Raf-1 protein kinase is required for growth of induced NIH/3T3 cells.
Many growth factors regulate the cytoplasmic Raf-1 protein kinase, consistent with its having a central role in transduction of growth signals. The kinase is ubiquitously expressed and can promote proliferation, presumably in a manner dependent on growth-factor receptors and membrane-associated oncogenes. We have now examined the dependence of serum- and TPA (12-O-tetradecanoylphorbol-13-acetate)-regulated NIH/3T3 cell growth on RAF-1 kinase to determine whether Raf-1 is essential for receptor signalling. We inhibited Raf-1 function by expressing c-raf-1 antisense RNA or kinase-defective c-raf-1 mutants. Antisense RNA for c-raf-1 interferes with proliferation of normal NIH/3T3 cells and reverts raf-transformed cells. In revertant cells, DNA replication induced by serum or TPA was eliminated or reduced proportionately to the reduction in Raf protein levels. Expression of a kinase-defective Raf-1 mutant (craf301) or a regulatory domain fragment (HCR) inhibited serum-induced NIH/3T3-cell proliferation and raf transformation even more efficiently. Inhibition by antisense RNA or craf301 blocked proliferation and transformation by Ki- and Ha-ras oncogenes. We conclude that raf functions as an essential signal transducer downstream of serum growth factor receptors, protein kinase C and ras.
Caveat emptor or blissful ignorance? Patients and the consumerist ethos.
The notion that consumerist behaviour is, or should be, prevalent amongst individuals seeking health care has underlain recent United States and British governmental policy directives. Consumer groups make similar assumptions when exhorting individuals to treat health care like any other service. This paper enquires to what extent patients conceive of themselves and others as adopting consumerist behaviour when seeking and evaluating primary health care. Three hundred and thirty-three patients attending general practices in Sydney, Australia, were asked in open-ended questions to state why they chose their regular doctor, why they continued to visit that doctor, if they had ever changed their doctor, if they thought most people could tell if a doctor were good or bad, and what qualities they thought constituted a good and bad doctor. It is concluded that the patients surveyed tended not to think of themselves as consumers who should be wary of the quality of service offered by doctors. Rather they preferred to trust their doctor, and therefore did not devote effort to actively seeking out information about their doctor or evaluating his or her services.
Strategies used to communicate route directions by telephone: a comparison of the performance of 7-year-olds, 10-year-olds and adults.
Standard outcome measures used in a referential communication (route finding) task showed that 7-year-olds were inferior to 10-year-olds and adults in terms of adequacy of messages provided (as speakers) and selection of referent (as listeners). Because the task involved negotiation of route directions by telephone, a richer dialogue resulted than is usual in referential communication studies. This made possible an analysis of the strategies used and revealed differences untapped by the standard measures. The types of strategies used (components, numbering, directional, minimal) varied as a function of age, with the adults using much directional information and the children very little. Much of the younger children's description was either minimal or used inadequately specified mature strategies. Adults frequently used dual strategies (e.g. directional + numbering). Older children showed little evidence of these individually but achieved them, in practice, through dialogue with their partners. Age differences in quantity of communication (number of turns) were found to be linked to strategy use. The advantages of the telephone as an experimental medium of communication are discussed.
Primary health care consumerism amongst elderly Australians.
Despite acceptance of many of the principles justifying government intervention in health care provision and financing, much recent market-based policy in Australia, the USA and the UK has been based on the assumption that patients have the potential to behave as 'good consumers'. Good consumers are patients with the ability and desire to seek out health care of good quality and reasonable cost. In this paper, an exploratory survey of general practice attenders in Western and Northern Sydney is reported. The aim of the survey was to assess the extent to which patients critically select and evaluate their general practitioner, as a good consumer may be expected to do. The results demonstrate a lack of consumer-oriented behaviour both in general and amongst older respondents in particular. If such results hold true, market-based health care policies relying on consumers to judge quality of care are likely to be detrimental to the health of older people.
Lack of enzyme induction with oxcarbazepine (600 mg daily) in healthy subjects.
1. Oxcarbazepine (OXC), the 10-keto analogue of carbamazepine (CBZ), has similar anticonvulsant efficacy and possibly improved patient tolerability. Unlike CBZ, it is metabolised by reduction and may not induce hepatic monooxygenase enzymes. 2. Serum concentrations of OXC and its active metabolite 10-OH-carbazepine (10-OH-CZ) were followed after a single 300 mg dose and during and after 300 mg OXC twice daily for 29 doses in eight healthy male volunteers. 3. Antipyrine metabolism, urinary 6-beta-hydroxycortisol excretion, sex hormone binding globulin (SHBG) levels and circulating androgens were measured as indices of hepatic enzyme induction before, during and after treatment with OXC. 4. Elimination half-lives (mean +/- s.e. mean) of 10-OH-CZ were unaltered by 2 weeks' therapy with OXC (before 11.3 +/- 1.1 h; after 13.9 +/- 3 h). Trough plasma concentrations of 10-OH-CZ at steady-state (31 +/- 2.2 mumol l-1) were higher than predicted (16.5 +/- 4 mumol l-1). 5. Antipyrine metabolism, urinary 6-beta-hydroxycortisol excretion, SHBG levels and circulating androgens were unaltered by treatment with OXC. 6. OXC (600 mg daily) does not induce hepatic monooxygenase enzymes and so is likely to have more predictable dose-concentration relationships and to produce fewer physiological and pharmacological interactions than CBZ.
Relationship between systemic drug absorption and gastrointestinal transit after the simultaneous oral administration of carbamazepine as a controlled-release system and as a suspension of 15N-labelled drug to healthy volunteers.
1. Plasma drug concentrations after a single oral administration of a suspension of carbamazepine (CBZ) and a 20/200 CBZ Oros osmotic pump system were measured in eight healthy male volunteers. The oral suspension contained 100 mg CBZ labelled with the stable isotope nitrogen-15, whilst the Oros contained 200 mg unlabelled CBZ. Plasma concentrations of [15N]-CBZ and CBZ were measured simultaneously by gas chromatography-mass spectrometry. 2. The position of the CBZ Oros (labelled with indium-111) in the gastrointestinal tract was followed by gamma scintigraphy. Plasma drug concentrations after the two treatments were used to relate pharmacokinetic with transit data. 3. The Oros was taken after breakfast and gastric emptying occurred between 1.1- greater than h post-dosing (median, 5.3 h). Small intestinal transit times ranged from 1.5- greater than 3.6 h, with a median of 2.2 h. There were wide individual variations in colonic transit, and the total transit time ranged from 10-60 h (median, 22 h). 4. Relative systemic bioavailability of CBZ from the Oros was reduced compared with that from the suspension (mean dose normalised AUC ratio = 0.69 +/- 0.17; mean dose-normalised AUC ratio = 0.85 +/- 0.13, allowing for actual release from the Oros system). 5. The in vivo absorption of drug into the systemic circulation from the Oros was estimated using the Wagner-Nelson method. This showed that absorption of CBZ was rapid when the Oros was present in the stomach and small intestine, the rate being determined by the release of drug from the system.(ABSTRACT TRUNCATED AT 250 WORDS)
Consumerism in the health care setting: an exploratory study of factors underlying the selection and evaluation of primary medical services.
Recent policy initiatives in Australia have continued the debate concerning the appropriate model of health care for this country. A market economy model, predicated on the existence of true consumerism, has been promoted by influential organisations to replace the current system. To test the validity of this perception and to explore the level of consumerism which exists in the Australian health care setting, we undertook a cross-sectional survey of general practitioner attenders in the outer western and northern suburbs of Sydney. Three hundred and thirty-three patients from six general practices were polled over a two-week period in March 1990. Far from demonstrating consumerist behaviour (especially the considered selection and evaluation of services), the survey population was strongly attracted to the traditional model of medical care, which is characterised by the trusting and dependent relationship of patients with their doctors.
Heart attack. A personal account.
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Comparison of the pharmacokinetics and pharmacodynamics of unformulated and formulated 4-hydroxyandrostenedione taken orally by healthy men.
A study of the aromatase inhibitor 4-hydroxy-androstenedione (4-OHA) was conducted in normal healthy men to compare the oral administration of two preparations of the drug: an unformulated, micronized powder and a formulated microcrystalline material (CGP 32349). The formulated material achieved a significantly higher mean peak concentration (88% greater than that obtained using the unformulated powder) and a higher mean AUC (not significant). The median time to peak was 1.5 h for both preparations and the elimination rate constants were similar (0.31 for micronized 4-OHA and 0.36 h-1 for formulated 4-OHA). Plasma concentrations of 4-OHA in this group were markedly lower than those previously observed in postmenopausal breast cancer patients. Significant biological activity was demonstrated with the formulated material in its suppression of plasma oestradiol levels, whereas no significant suppression was obtained using the micronized powder. An increase in androgen levels was observed that may have been due to competitive inhibition of enzymes involved in metabolic clearance of androgens and/or to decreased feedback inhibition of gonadotrophin secretion by oestradiol.
Spinal antinociceptive synergy between clonidine and morphine, U69593, and DPDPE: isobolographic analysis.
The spinal antinociceptive interaction between the opiate receptor subtype agonists morphine (mu), U69593 (kappa) and [D-Pen2,5]-enkephalin (DPDPE; delta) with clonidine (alpha 2 adrenergic) was examined. Male SD rats received fixed ratios of clonidine to morphine (10:1), U69593 (1:3), or DPDPE (10:1) through catheters terminating at the lumbar cord. Graded dose-response curves (DRC) were constructed from tail-flick latencies converted to % maximal possible effect (%MPE), and the ED50 calculated. The DRCs of morphine and U69593 but not of DPDPE were parallel to the DRC of the opiate plus clonidine. Synergy was determined by isobolographic analysis. The ED50 values for the mixtures were significantly less than the theoretical additive ED50 values, indicating synergy between clonidine and morphine, U69593, or DPDPE.
Antinociceptive interaction between opioids and medetomidine: systemic additivity and spinal synergy.
The antinociceptive interaction on the tail flick (TF) and hot plate (HP) tests between opioid analgesics and medetomidine after intravenous (iv) or intrathecal administration were examined by isobolographic analysis. Male Sprague-Dawley rats received fixed ratios of medetomidine to morphine, fentanyl, and meperidine of 1:10 and 1:30, 10:1, and 1:3, respectively, by iv administration or 10:1, 3:1 and 10:1, and 1:3 by intrathecal administration, respectively. Data were expressed as the percentage maximal possible effect (%MPE). The A50 (dose producing 50% MPE) for each drug or drug combination was determined from the dose-response curve. Isobolographic analysis revealed that the effect of medetomidine combined with fentanyl, morphine, or meperidine was additive after iv administration. The intrathecal administration of combinations of medetomidine with the opioids produced a synergistic antinociceptive effect in the TF but not HP test. These data confirmed that the interaction between medetomidine and opioids in producing antinociception may be additive or synergistic, depending on the route of administration, drug ratio administered, and level of processing of the nociceptive input (i.e., spinal vs. supraspinal). Moreover, these results were consistent with a spinal role for alpha-2 adrenoceptors in mediating antinociception. The authors suggest that the interaction between the opioid and alpha-2 adrenergic receptors occurs within the spinal cord.
Mutational activation of c-raf-1 and definition of the minimal transforming sequence.
A series of wild-type and mutant raf genes was transfected into NIH 3T3 cells and analyzed for transforming activity. Full-length wild-type c-raf did not show transforming activity. Two types of mutations resulted in oncogenic activity similar to that of v-raf: truncation of the amino-terminal half of the protein and fusion of the full-length molecule to gag sequences. A lower level of activation was observed for a mutant with a tetrapeptide insertion mapping to conserved region 2 (CR2), a serine- and threonine-rich domain located 100 residues amino-terminal of the kinase domain. To determine essential structural features of the transforming region of raf, we analyzed point and deletion mutants of v-raf. Substitutions of Lys-56 modulated the transforming activity, whereas mutation of Lys-53, a putative ATP binding residue, abolished it. Deletion analysis established that the minimal transforming sequence coincided precisely with CR3, the conserved Raf kinase domain. Thus, oncogenic activation of the Raf kinase can be achieved by removal of CR1 and CR2 or by steric distortion and requires retention of an active kinase domain. These findings are consistent with a protein structure model for the nonstimulated enzyme in which the active site is buried within the protein.
Probing structure and function of the raf protein kinase domain with monoclonal antibodies.
Five monoclonal antibodies were generated against the raf kinase domain. All antibodies react with different isozymes of the raf family, as well as Raf proteins from different species, albeit with differential affinities. Epitope mapping showed all five epitopes clustered in the vicinity of the conserved APE sequence. Although thought to be an essential part of the catalytic site, antibody binding to that domain does not affect kinase activity in vitro or the capability to specifically associate with other cellular proteins. Based on a detailed dissection of the epitopes, a comparative analysis of secondary structure predictions indicates a common structural motif in that region, which is highly conserved amongst protein kinases of the serine/threonine as well as the tyrosine class.
An isobolographic analysis of the antinociceptive effect of systemically and intrathecally administered combinations of clonidine and opiates.
The antinociceptive interaction of opiate analgesics with clonidine was examined with the tail-flick and 55 degrees C hot plate tests. Male Sprague-Dawley rats received fixed ratios of clonidine to fentanyl, meperidine or morphine by i.v. and intrathecal injection. Data are expressed as percentage of maximal possible effect and the dose producing 50 percentage of maximal possible effect for each drug or drug combination is used to index potency. The rank order of potency in both tests after i.v. administration is fentanyl much greater than clonidine greater than meperidine greater than or equal to morphine and after intrathecal administration it is morphine greater than fentanyl much greater than clonidine much greater than meperidine. Isobolographic analysis shows that the effect of clonidine combined with an opiate is additive after i.v. administration; the exception is that morphine and clonidine are synergistic in the hot plate test. The intrathecal combinations of clonidine with morphine or meperidine produces a supra-additive antinociceptive effect in the tail-flick test but not in the hot plate test. Fentanyl does so in both tests. These data confirm a positive interaction between clonidine and opiates in producing antinociception. This interaction may be additive or synergistic, depending on route of administration and the nociceptive test used. The timing of injections and pharmacokinetic factors may also influence the results. Moreover, these results suggest that the interaction between the opiate and alpha-2 adrenergic receptors occurs within the spinal cord.
ILO charter of justice for nurses.
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A symposium on occupational health. Development in the UK.
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Where does the OH nurse fit in?
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