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Biomedical subjects

R T Jackson

Publications and source records attributed to R T Jackson.

At least 37 records · Page 2Linked to original sources
PubMed1997

A predictive model of the health benefits and cost effectiveness of celiprolol and atenolol in primary prevention of cardiovascular disease in hypertensive patients.

This study compares the antihypertensive and lipid modifying effects of treatment of mild to moderate hypertension with celiprolol or atenolol. It also models the 5-year cardiovascular risk reduction and the cost effectiveness of monotherapy from a partial societal perspective. The effects of celiprolol and atenolol on systolic blood pressure (SBP), total serum cholesterol (TC) and high density lipoprotein cholesterol (HDL-C) were obtained from a pooled analysis of published studies. Although celiprolol and atenolol had similar effects on SBP, celiprolol reduced the ratio of TC to HDL-C by 10.2% [95% confidence intervals (95% CI) -16.4%, -4.0%) but atenolol increased the ratio by 7.7% (95% CI of 3.4%, 12.0%). The 5-year absolute risks of an initial coronary or cerebrovascular event or cardiovascular death were computed for cohorts of patients treated with either agent or remaining untreated, using an accelerated failure time (AFT) model, based on Framingham Heart Study data. Inputs to the model were age, gender, smoking status, SBP, TC and HDL-C. The change in absolute risk was estimated using the changes in SBP and TC: HDL-C obtained from the pooled analysis. Average life-months gained by therapy were computed as differences between the Kaplan-Meier survival curves estimated from the model plus differences in 5-year cardiovascular death rates multiplied by average life expectancy obtained from life tables. Direct medical costs included drug treatment, and the costs of acute care for initial coronary and cerebrovascular events deferred by therapy over the 5-year treatment period. The model shows that in the lowest-risk base case (60-year-old men who are nondiabetic and nonsmokers with SBP of 160 mm Hg and a 5-year absolute cardiovascular risk of 12%), celiprolol (271 mg/day) is 2-fold more effective than atenolol (77.4 mg/day) in reducing coronary event risk, and equally effective in reducing cerebrovascular event risk. The number of individuals that would have to be treated for 5 years to avoid 1 coronary event is about 30 for celiprolol versus 70 for atenolol. Therapy with celiprolol yields more life-months and at current prices, the cost per life-year gained by therapy is significantly lower. Both drugs are cost effective by international standards in the treatment of patients with 5-year absolute cardiovascular risk greater than 10%, and are more cost effective in those patients at higher levels of absolute cardiovascular risk. The direct medical costs of treatment for 5 years with celiprolol are the same or slightly less than treatment with atenolol at the dosages used in the clinical trials, despite a 19% higher tablet price. Both drugs are more cost effective in patients at higher levels of absolute cardiovascular risk. These findings are sensitive to the drug dosages, tablet prices and the discount rate. Based on epidemiological and clinical data, replacing atenolol with celiprolol in patients with mild to moderate hypertension, but without overt cardiovascular disease, is predicted to have similar effects on stroke risk, but to be substantially more effective in reducing the risk of coronary events at no additional direct medical cost over a 5-year treatment period.

Adrenergic beta-Antagonists↗
PubMed1997

Ehrlichiosis with systemic sepsis syndrome.

The diversity of presenting symptoms with Ehrlichia infections makes diagnosis difficult. Rash is infrequent. A febrile illness in the summer with thrombocytopenia should arouse suspicion of possible ehrlichiosis.

Diagnosis, Differential↗
PubMed1996

Head extension and age-dependent posturographic instability in normal subjects.

We have investigated the role of head extension in posturographic testing of normal subjects. We especially wished to determine the number of falls that occurred in the "normal" elderly so as to distinguish them from elderly patients with abnormal neurologic and vestibular patterns. We tested 144 normal subjects ages 22 to 85, the majority older than 60 years, with the NeuroCom Equitest sensory posturography protocol: first with their heads erect and then with their heads extended 55 degrees. None of our subjects younger than age 59 experienced a fall during sensory posturography tests with their heads erect. However, 35 of the 101 older subjects exhibited a total of 79 falls during these same tests. When the tests were repeated with the head extended 55 degrees, the number of falls for the whole group increased from 79 to 171. Where only 24% of all the subjects fell with head erect, 52% fell with head extended. The increase was especially notable among the elderly. Head extension increases the difficulty of performing certain posturography tests and has been useful in uncovering compensated deficits in equilibrium in young and middle-aged patients. However, because head extension significantly increases falls among normal elderly subjects, this does not seem to be an effective tool to determine abnormality in this age group.

Accidental Falls↗
PubMed1995

A cocaine-sensitive active dopamine transport in human lymphocytes.

Human lymphocytes possess a cocaine-sensitive high-affinity transport system for [3H]dopamine. [3H]Dopamine uptake was saturated with increasing dopamine concentrations and followed Michaelis-Menten kinetics. The uptake was temperature, sodium, and chloride dependent and was affected by the co-addition of ouabain, phloridzin, potassium cyanide, gramicidin, and other metabolic inhibitors. The uptake of dopamine was blocked significantly in a concentration-dependent manner by cocaine and its congeners. Furthermore, preliminary evidence is presented linking the possible relationship between decreased lymphocyte [3H]dopamine uptake and chronic cocaine abuse in humans.

Adult↗
PubMed1995

Abnormalities in posturography and estimations of visual vertical and horizontal in multiple sclerosis.

Twenty-seven patients with mild multiple sclerosis were tested with the dynamic posturography protocol used in the NeuroCom Equitest procedure. The purpose of this study was to determine if the standard test procedure elicited a pattern of responses that would suggest the possibility of multiple sclerosis during differential diagnosis of a patient with dysequilibrium. In addition, the patients' ability to align a light bar to vertical and horizontal was tested with the head erect and with the head tilted 45 degrees to the right and left shoulder. There was a pattern of abnormality in the Equitest motor coordination tests. Only one patient produced normal scores in both the latency and adaptation tests. No pattern of error was noted in the sensory organization tests. In the visual alignment tests, only 3 of the 27 patients tested produced values that were within normal limits for the three different head positions. Visual alignment and the motor coordination tests are not specific for multiple sclerosis, but poor performance probably indicates a disruption of the integration of visual, vestibular, and somatosensory information. Although patients with early multiple sclerosis and patients with purely vestibular disorders often have similar complaints, they have quite different profiles of abnormalities in posturography testing.

Diagnosis, Differential↗
PubMed1995

Oil-on-water: proposed method for intraoperative identification of perilymphatic fistula.

The intraoperative diagnosis of a perilymphatic fistula is usually subjective and controversial. Unless there is profuse gushing of fluid, there is no reliable, objective, intraoperative indicator of a perilymphatic fistula. The authors suggest a technique for the real-time determination of the existence and location of a perilymphatic fistula: visualization of clear perilymphatic fluid beneath a layer of mineral oil. Mineral oil is transparent to visible light, hydrophobic, and lighter than perilymphatic fluid. The oil traps the aqueous fluid, and tends to keep it contained in a droplet. With standard otomicroscopic viewing, a droplet of less than 1 microL of fluid is readily visible through the oil. In vitro temporal bone studies showing the utility and objectivity of identifying the aqueous fluid in the mesotympanum are reported. Mineral oil floats on saline and is readily removed with suction-irrigation techniques. The authors consider the oil-on-water technique to increase the resolution of identifying minute aqueous droplets and recommend in vivo study in patients.

Cochlear Aqueduct↗
PubMed1994

The validity of Maori hospital discharge statistics for ischaemic heart disease in New Zealand.

Data from an Auckland coronary heart disease register for the years 1983 to 1991 have been used to assess the validity of routine national statistics on Maori hospital discharge rates for ischaemic heart disease. Ethnicity as recorded on the hospital admission record was compared with self defined ethnicity as recorded by register interviewers. Unlike routine New Zealand mortality statistics, where there is marked underreporting of Maori mortality, it appears that hospital discharge statistics are not markedly affected by misclassification of ethnicity. Approximately 12% of those classified on the admission record as Maori considered themselves to be of a different ethnicity, and 0.5% of those classified as 'other' considered themselves to be Maori. Because of the small proportion of the population (and of ischaemic heart disease deaths) who are Maori, the two misclassifications cancel out and the overall routinely reported hospital morbidity rates are similar to rates based on self reported ethnicity. For example, in 1990, routine national statistics show that there were 345 Maori hospital discharges or deaths due to ischaemic heart disease, and 8946 events among other ethnic groups. After adjustment using the register figures to reflect self defined ethnicity, the figures were 347 and 8944 respectively.

Humans↗
PubMed1994

Expression of a high-affinity serotonin transporter in human lymphocytes.

This study was undertaken to assess the capability of lymphocytes to actively transport serotonin (5-HT). The data we obtained showed that lymphocytes isolated from the blood of normal human subjects contained a high-affinity uptake system for [3H]5-HT. Kinetic analysis of the uptake data as computed by regression analysis from Lineweaver--Burk plots, yielded a Km of 180 +/- 20 nM and Vmax of 94 +/- pmole/10(7) cells. The uptake of [3H]5-HT was temperature, sodium and chloride dependent and was potently inhibited by the antidepressants clomipramine, imipramine, fluoxetine and fluvoxamine, which are specific for the 5-HT transporter. Compounds that are more selective for norepinephrine and dopamine transporters such as mazindol, desipramine, and GBR 19209 had a lower inhibitory effect on the uptake of [3H]5-HT in human lymphocytes. The expression of a 5-HT transporter in human lymphocytes that resembles 5-HT uptake by platelets and brain synaptosomes may provide insights into the potential role of 5-HT in immune function and its relationship to the neurobiology of affective and addictive disorders.

Adult↗
PubMed1994

Active [3H]-dopamine uptake by human lymphocytes: correlates with serotonin transporter activity.

The main objective of the present investigation was to determine whether the uptake of [3H]-dopamine in human lymphocytes is mediated through a serotonin transporter. This was examined by studying the effects of various monoamine uptake inhibitors on the uptake of [3H]-dopamine in human lymphocytes. Among the compounds tested, indatraline, imipramine and fluoxetine, selective inhibitors of neuronal serotonin transporter, were the most potent inhibitors of [3H]-dopamine uptake in lymphocytes. The 50% inhibiting concentration (IC50) for these inhibitors was in the range of 3.5-17 nmol/l. Bupropion, GBR 12909, nomifensine and xylamine, selective inhibitors of dopamine and norepinephrine transporters, had low affinity for the dopamine uptake system in human lymphocytes with IC50 values ranging between 1,000 and 40,000 nmol/l. These findings provide supportive evidence for the participation of a serotonin transporter in the uptake of [3H]-dopamine in human lymphocytes. The existence of a high affinity transport system for dopamine and serotonin in human lymphocytes may serve as a readily accessible model to detect changes in the neuronal uptake of dopamine and serotonin in addictive and psychiatric disorders.

Adult↗
PubMed1993

Analysis of case-crossover designs.

The case-crossover design provides a means to study the effects of transient exposures on the risk of acute illness, for example, the effects of drinking alcohol on the immediate risk of a heart attack. Only cases are required by the design, since each case is effectively its own control; what a case was doing at the time of an acute event is compared with what the case would have been doing usually. Maclure has described an approach based on the Mantel-Haenszel method of analysis. It is shown here how the analysis of case-crossover designs can be achieved by a method of maximum likelihood. The method is quite general and, in principle, can be used to analyse the joint effects of many transient exposures. For binary exposures the Mantel-Haenszel approach is an approximate solution to the likelihood equations. In practice, case-crossover designs are limited by the information available on each case's 'usual' behaviour. Extracting such information requires in-depth questioning, but, in principle, it can be obtained. To do so requires careful questionnaire design. The approach is illustrated by analysis of 24 hour alcohol consumption and the risk of myocardial infarction. The problem with this analysis is how to estimate the probability of what a case would 'usually' have been doing from information on drinking frequency.

Adult↗
PubMed1992

Effect of astemizole on antigen-mediated histamine release from the blood of patients with allergic rhinitis.

The main objective of this study was to test the effectiveness of astemizole in vitro in blocking the release of histamine from blood of patients with allergic rhinitis. The results of this investigation indicated that astemizole inhibited allergen-mediated histamine release from blood basophils of patients with this allergic disorder. The inhibition by astemizole (33-156 mumol) was immediate, requiring no pre-incubation of the cells, and was dose-dependent, with maximal inhibition of about 91%. The relatively high potency of astemizole in inhibiting the immunologic release of histamine may provide an additional measure in the treatment of allergic rhinitis with this H1-receptor antagonist.

Adolescent↗
PubMed1991

Interaction of cocaine with nasal mucosa.

Canine nasal mucosa was studied in vitro to examine (1) the production of vasoconstriction by cocaine and, (2) the epithelial permeability of cocaine. Cocaine, by itself, failed to induce any contraction of the nasal blood vessels but did enhance contractions resulting from electrical stimulation or addition of norepinephrine. Results indicate that cocaine produces vasoconstriction by blocking the reuptake of endogenous norepinephrine rather than any direct action on vascular smooth muscle. Cocaine was found to be three times more permeable than sucrose, which has a similar molecular weight. The transepithelial permeability of cocaine was independent of direction and did not display competition. Results indicate that cocaine permeates by simple diffusion and that the relatively high permeability is due to a greater lipid solubility. Cocaine was found to accumulate in the nasal mucosa. A significant portion of the accumulation is associated with specific sites that are characteristic of catecholamine uptake sites.

Animals↗