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Biomedical subjects

A Jackson

Publications and source records attributed to A Jackson.

At least 109 records · Page 6Linked to original sources
PubMed2000

Informed consent for labour epidurals: what labouring women want to know.

PURPOSE: To determine A) what a labouring woman expects to hear about epidural analgesia before consenting, B) if she feels able to understand the risks and thereby assess if we are obtaining informed consent. METHODS: Sixty actively labouring women were surveyed immediately after requesting an epidural. Demographic, labour, epidural and consent information were included in the questionnaire. Answers were categorical (yes/no, multiple choice) or scored on a scale from 0 to 10 (visual analogue scale). RESULTS: The majority of parturients wanted all potential epidural complications but not their incidences disclosed in the consent process. However, a discussion of risks would not dissuade women from consenting to an epidural in the majority of cases. Labouring women have a moderate understanding of epidural risks. The ability to understand risks was not affected by labour pain, anxiety, opioid premedication, duration of labour pain, desire for an epidural, previous epidural experience, level of education or age. CONCLUSION: This prospective survey characterizes what 60 reasonable labouring women wanted to know about labour epidural analgesia. Parturients wanted all risks of epidural analgesia disclosed in the informed consent process. The majority of women did not want the incidences quoted. This study suggests that labouring patients are as able to give informed consent as are other members of our patient population.

Adult↗
PubMed2000

Expression of flavour preferences conditioned by caffeine is dependent on caffeine deprivation state.

RATIONALE: The acquisition of a caffeine conditioned flavour preference depends on the caffeine deprivation status of subjects during conditioning. It is not known if the expression of an established flavour preference is also state-dependent. OBJECTIVES: To determine if the expression of a flavour preference conditioned by caffeine is dependent on the level of deprivation at the time of testing. METHODS: In a double-blind placebo controlled study, 44 subjects were given 4 days exposure to a novel flavoured drink following overnight abstinence from caffeine. Half the subjects received caffeine (100 mg) in the drink, while the remainder had placebo (maltodextrin, 100 mg). Subjects rated the pleasantness of the drink each time. On a fifth (test) day, the subjects were given additional caffeine (100 mg) or placebo 2 h before consuming and rating the pleasantness of the drink. RESULTS: Pleasantness ratings for the novel drink increased over the 4 conditioning days in subjects receiving caffeine, but decreased in those given placebo. On day 5, subjects who were trained and tested in the same caffeine deprivation state expressed pleasantness ratings similar to those for the final training day. In contrast, subjects who were trained and tested in different states expressed pleasantness ratings that were significantly different from those of the final training day. CONCLUSIONS: These results suggest that the expression of caffeine conditioned flavour preferences are acutely sensitive to current motivational state, and a number of possible explanations are discussed.

Adult↗
PubMed2000

High-resolution magnetic resonance and volume rendering of the labyrinth.

Our aim was to verify the feasibility of volume rendering (VR) of high-resolution magnetic resonance (HR-MR) data sets of the labyrinth. We retrospectively reviewed the HR-MR data sets of 16 consecutive patients with no MR evidence of labyrinthine pathology. High-resolution MR data sets were obtained by means of a 3D T2-weighted FSE sequence with the use of a 3-in. circular surface coil for signal reception, and processed with a high-end workstation. Two reviewers performed separately VR of the labyrinth by selecting the signal intensity interval for attribution of opacity and transparency. Concerning the time taken for definition of the volume of interest, the two observers needed, respectively, 28.9 and 33.1 min (SD +/- 8.7-9.5 min), whereas the time taken for VR was respectively, 26 and 33.2 min (SD +/- 8.8-8.9 min). Concerning the selection of the signal intensity interval, the two observers had, respectively, 86.4 and 88.7 mean lower threshold (SD +/- 34.5-33.5), 488.9 and 495.4 mean upper threshold (SD +/- 56.3-53.8). In our experience, we have found VR of HR-MR to offer a reliable and reproducible technique for producing 3D representations of the labyrinth. The VR algorithms use all data within the imaging volume and optimize the dynamic range ascribed to the object being visualized.

Adolescent↗
PubMed2000

Predictions derived from modelling the hippocampal role in navigation.

A computational model of the lesion and single unit data from navigation in rats is reviewed. The model uses external (visual) and internal (odometric) information from the environment to drive the firing of simulated hippocampal place cells. Constraints on the functional form of these inputs are drawn from experiments using an environment of modifiable shape. The place cell representation is used to guide navigation via the creation of a representation of goal location via Hebbian modification of synaptic strengths. The model includes consideration of the phase of firing of place cells with respect to the theta rhythm of hippocampal EEG. A series of predictions for behavioural and single-unit data in rats are derived from the input and output representations of the model.

Animals↗
PubMed2000

Factors elevating cAMP attenuate the effects of 8-OH-DPAT on lordosis behavior.

The effects of a soluble derivative of forskolin and of two membrane-permeable analogs of cAMP, dibutyryl cAMP, and 8-bromo-cAMP, on the ability of a serotonin (5-HT)(1A) receptor agonist to inhibit lordosis behavior were examined. Sexually receptive, proestrous rats received a bilateral infusion into the ventromedial nucleus of the hypothalamus (VMN) with 68 ng of the forskolin derivative 1, 1.5, 2, or 2.5 h prior to infusion with 200 ng of the 5-HT(1A) receptor agonist, (+/-)-8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT). Proestrous rats and ovariectomized rats, hormonally primed with 25 microg estradiol benzoate and 500 microg progesterone, were coinfused with 200 ng 8-OH-DPAT and either 50 microg dibutyryl cAMP or 5 microg 8-bromo-cAMP. In proestrous rats, prior infusion with the forskolin derivative reduced the effects of the 5-HT(1A) receptor agonist on lordosis behavior. The best protection occurred at 2 h; by 2.5 h after the preinfusion, any protective effect had disappeared. Coinfusion with either dibutyryl-cAMP or 8-bromo-cAMP reduced the effects of 8-OH-DPAT in proestrous rats. In hormone-primed, ovariectomized rats, dibutyryl cAMP offered significant protection against the effects of 8-OH-DPAT, but there was no protection with 8-bromo-cAMP. These findings are consistent with the speculation that 8-OH-DPAT's inhibition of lordosis behavior results, in part, from an inhibition of adenylyl cyclase, resulting from agonist activation of 5-HT(1A) receptors in the VMN. The findings are also consistent with our earlier observations for differences between proestrous rats and hormone-primed, ovariectomized rats in their response to 5-HT receptor-active compounds.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed2000

Behavioural effects of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate-receptor antagonists and their relevance to substance abuse.

This review presents some of the work that has been carried out to investigate the behavioural effects of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA)-receptor antagonists in animal models of substance abuse. Many of the studies have been conducted in light of current ideas that emphasise the analogous role of glutamatergic mechanisms in synaptic plasticity and long-term behavioural adaptation to drugs. Experiments on behavioural sensitisation indicate that whereas N-methyl-D-aspartate receptors are involved in induction, AMPA-receptors may mediate expression of the established response. In this regard, an important factor may be the degree of drug-environment conditioning. Thus, studies of the effects of AMPA-receptor antagonists on conditioned behaviours are reviewed here. Relatively few studies on the effects of AMPA-receptor antagonists on primary reinforcement from self-administered drugs and the subjective effects of drugs have been carried out, but a profile that contrasts with that of the N-methyl-D-aspartate antagonists appears to be emerging. Studies of withdrawal from opioids suggest that whilst AMPA-receptor antagonists may not be able to prevent tolerance or dependence from developing, they may ameliorate both the physical and emotional consequences of withdrawal. Overall, the AMPA-receptor antagonists may represent a promising new approach for treating the consequences of drug abuse. However, as results are often complicated by the use of the less-selective compounds, it will be important to use better tools in future studies.

Animals↗
PubMed2000

Clinical experience with intensity modulated radiation therapy (IMRT) in prostate cancer.

PURPOSE: To compare acute and late toxicities of high-dose radiation for prostate cancer delivered by either conventional three-dimensional conformal radiation therapy (3D-CRT) or intensity modulated radiation therapy (IMRT). MATERIALS AND METHODS: Between September 1992 and February 1998, 61 patients with clinical stage T1c- T3 prostate cancer were treated with 3D-CRT and 171 with IMRT to a prescribed dose of 81 Gy. To quantitatively evaluate the differences between conventional 3D-CRT and IMRT, 20 randomly selected patients were planned concomitantly by both techniques and the resulting treatment plans were compared. Acute and late radiation-induced morbidity was evaluated in all patients and graded according to the Radiation Therapy Oncology Group toxicity scale. RESULTS: Compared with conventional 3D-CRT, IMRT improved the coverage of the clinical target volume (CTV) by the prescription dose and reduced the volumes of the rectal and bladder walls carried to high dose levels (P<0.01), indicating improved conformality with IMRT. Acute and late urinary toxicities were not significantly different for the two methods. However, the combined rates of acute grade 1 and 2 rectal toxicities and the risk of late grade 2 rectal bleeding were significantly lower in the IMRT patients. The 2-year actuarial risk of grade 2 bleeding was 2% for IMRT and 10% for conventional 3D-CRT (P<0.001). CONCLUSIONS: The data demonstrate the feasibility and safety of high-dose IMRT for patients with localized prostate cancer and provide a proof-of-principle that this method improves dose conformality relative to tumor coverage and exposure to normal tissues.

Aged↗
PubMed2000

Is the clinical expression of late-life depression influenced by brain changes? MRI subcortical neuroanatomical correlates of depressive symptoms.

BACKGROUND: "Vascular depression" has recently been proposed. It is characterized by magnetic resonance imaging (MRI) T2-weighted subcortical lesions, a late onset of first episode of depression, and reduced heritability; a cerebrovascular etiology is suggested. The validity of "vascular depression" might be strengthened if an association was found between the subcortical lesions used to define it and particular depressive symptoms. METHODS: A blinded cross-sectional examination of DSM-III-R depressive symptoms (American Psychiatric Association, 1987) and MRI T2-weighted subcortical lesions in 44 patients with late-life depression. RESULTS: Many associations were found; however, because of multiple comparisons, their significance is viewed with caution. The most robust finding was that psychomotor retardation was independently related to total white-matter score. The odds of showing psychomotor retardation was increased 1.9 times for every point increase in severity of white-matter change. CONCLUSION: In late-life depression the clinical expression of the depression is influenced by the pattern of MRI T2-weighted subcortical lesions. This gives some validity to the concept of an MRI-defined "vascular" subtype of late-life depression and strengthens the argument for including neuroimaging in the classification of late-life depression.

Aged↗
PubMed2000

Effect of the angiotensin-converting enzyme gene deletion polymorphism on the risk of venous thromboembolism.

Allele frequencies for the insertion/deletion (I/D) polymorphism of the angiotensin-converting enzyme (ACE) gene were determined in a large case-control study of 517 unselected patients with venous thromboembolism and 478 blood donors. The D allele frequency was 0. 53 [95% confidence interval (CI) 0.50-0.56] in patients and 0.54 (95% CI 0.50-0.57) in controls, giving an odds ratio for the D allele of 0.97 (95% CI 0.81-1.16). In the same population, the odds ratio for the factor V Leiden mutation (F5G1691A) was 6.9 (95% CI 4. 0-11.9). Therefore, the ACE I/D polymorphism is not a risk factor in a representative group of unselected patients with venous thromboembolism. The possibility that the I/D polymorphism is a risk factor for venous thromboembolism specifically after hip replacement cannot be excluded.

Arthroplasty, Replacement, Hip↗
PubMed2000

The effect of hyperoxia on cerebral blood flow: a study in healthy volunteers using magnetic resonance phase-contrast angiography.

A small decrease in cerebral blood flow (approximately 10%) in response to 100% oxygen (O2) administration is well recognized. This observation was based on human volunteer studies, which employed a nitrous oxide washout method for the measurement of cerebral blood flow. Because this method is now appreciated to be subject to potential errors we have examined the cerebral blood flow response to 100% oxygen using a magnetic resonance imaging technique to quantify changes in carotid and basilar artery flow. The study, was performed in 12 normal male subjects aged 23-42 years. We report decreases in cerebral blood flow ranging from 9 to 31% with a mean value of over 20%. The decrease in cerebral blood flow was greater in seven young subjects (aged 23-26 years) with decreases in cerebral blood flow of 19.3-31.4% (mean 26.8%). In five older subjects (aged 32-42 years), decreases in CBF were smaller (mean 16. 2%). The administration of 100% O2 was accompanied by a small decrease in end-tidal CO2 (3.7-7.1%), insufficient to explain the changes in cerebral blood flow. We conclude that the decrease in cerebral blood flow in response to O2 administration is greater than previously described and appears to be greater in young adults.

Adult↗
PubMed2000

Interaction of Bordetella pertussis with human respiratory mucosa in vitro.

The human respiratory tract pathogen Bordetella pertussis is the major cause of whooping cough in infants and young children, and also causes chronic cough in adults. B. pertussis infection damages ciliated epithelium in the respiratory tract. However, the interaction of the bacterium with the respiratory mucosa is poorly understood, and previous studies have either utilized animal tissue which may not be appropriate, or isolated cell systems which lack the complexity of the respiratory mucosa. We have studied the interaction of B. pertussis strain BP536 with human nasal turbinate tissue in an air-interface organ culture over 5 days. We have also compared infection by BP536 with two other strains, Tohama I and CN2992, to determine whether the interactions observed with BP536 are consistent, and, in both nasal turbinate and adenoid organ cultures at 24 h, to determine whether there were differences between tissue from different parts of the respiratory tract. BP536 adhered to cilia, most commonly at their base, and disorganized their spatial arrangement, they also adhered to damaged tissue and mucus, but very rarely to unciliated cells. Within the first 24 h there was a five-fold increase in bacterial density on ciliated cells, and the total number of adherent bacteria increased up to 96 h. Infection caused increased mucus at 24h and an increase in damaged epithelium from 72 h which involved both ciliated and unciliated cells. The number of residual ciliated cells did not decrease after 72 h. The three different strains of B. pertussis exhibited similar interactions with the mucosa, and there was no tissue specificity for adenoid or turbinate tissue. We conclude that B. pertussis adhered to multiple sites on the mucosa and caused hypersecretion and epithelial damage which are the pathological changes described in vivo.

Adenoids↗
PubMed2000

Dietary change through African American churches: baseline results and program description of the eat for life trial.

BACKGROUND: Eat for Life, a multicomponent intervention to increase fruit and vegetable (F & V) consumption among African Americans, is delivered through African American churches. METHODS: Fourteen churches were randomly assigned to one of three treatment conditions: 1) comparison; 2) culturally-sensitive multicomponent intervention with one phone call; and 3) culturally-sensitive multicomponent intervention with four phone calls. The intervention included an 18-minute video, a project cookbook, printed health education materials, and several "cues" imprinted with the project logo and a 5 A Day message. A key element of the telephone intervention was the use of motivational interviewing, a counseling technique originally developed for addictive behaviors. Major outcomes for the trial included total F & V intake, assessed by food-frequency questionnaires (FFQs) and 24-hour recalls, and serum carotenoids. Psychosocial variables assessed included outcome expectations, barriers to F & V intake, preference for meat meals, neophobia, social support to eat more F & V, self-efficacy to eat more F & V, and nutrition knowledge. RESULTS: Baseline mean F & V intakes across the three FFQs ranged from 3.45 to 4.28 servings per day. Intake based on a single 24-hour recall was 3.0 servings. Variables positively correlated with F & V intake included self-efficacy, outcome expectations, and a belief that F & V contain vitamins. Factors negatively correlated with intake include perceived barriers, meat preference, neophobia, and high-fat cooking practices. The completion rate for the first telephone counseling call was 90%. Completion rates for the remaining three calls ranged from 79% to 86%. CONCLUSION: The recruitment and intervention methods of the Eat for Life study appear promising. The telephone intervention based on motivational interviewing is potentially useful for delivering dietary counseling.

Adult↗
PubMed2000

Does experience predict knowledge and behavior with respect to cutaneous melanoma, moles, and sun exposure? Possible outcome measures.

A prospective survey of 3105 adults in 16 randomly selected group practices was conducted to test whether individuals with a personal experience, family history, or other contact with malignant melanoma display more knowledge and appropriate behavior with regard to melanomas and sun exposure than those with no such experience. Although patients with previous contact with the condition were more likely to check for moles, were more aware of the significance of changes in the shape of moles, and were more aware of the necessity for prompt treatment, they were not more knowledgeable about other important signs or more likely to protect themselves from sun exposure. Direct experience or contact with melanoma appeared to have some positive effects on knowledge, but there is no room for complacency for those at increased risk or those treating them. Both primary and secondary prevention for people who are vulnerable could be undertaken in primary care.

Adolescent↗
PubMed2000

Slipped capital femoral epiphysis: is the displacement always posterior?

The initial direction of displacement on slipped capital femoral epiphysis is generally accepted to be posterior as a consequence of retroversion of the femoral neck. We report the case of a 15-year-old boy with slipped capital femoral epiphysis in the medial direction, confirmed by three-dimensional computerized imaging. This was associated with an elongated neck without retroversion of the femoral neck. We suggest a correlation between elongated femoral neck with increased offset of the hip and the medial direction of slip. This case also underlines the need for precise definition of deformity prior to undertaking surgical treatment.

Adolescent↗
PubMed2000

Dynamic susceptibility contrast enhanced MRI in reversible posterior leukoencephalopathy syndrome associated with haemolytic uraemic syndrome.

We describe a case of reversible posterior leukoencephalopathy associated with haemolytic uraemic syndrome. Following remission confirmed on MRI, the patient relapsed several months later. Neuroimaging findings on conventional MRI and FLAIR sequences and dynamic susceptibility contrast enhanced MRI are described. White matter abnormalities may be shown on CT or MRI in this syndrome. However, dynamic susceptibility contrast enhanced MRI showed far more extensive abnormality within the brain. In addition, phase contrast angiographic measurement of flow in the carotid and basilar arteries indicated a significant elevation of cerebral blood flow, suggesting a decrease in global cerebrovascular resistance. These observations support existing theories that the disorder is manifested by autoregulatory disturbance in small cerebral vessels. Our findings suggest that this abnormality is far more extensive than is demonstrated on T2 weighted MR images and that it is associated with global abnormality of cerebrovascular autoregulation.

Adult↗