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Biomedical subjects

C A Jackson

Publications and source records attributed to C A Jackson.

At least 73 records · Page 4Linked to original sources
PubMed1988

The costs of employee smoking. A computer simulation of hospital nurses.

A computer simulation model of the economic impact of employee smoking on an employer was developed with a population of hospital nurses as the example. Net economic impact was calculated by estimating cumulative costs borne by the employer under various scenarios and comparing them with projected costs estimated from baseline data. The model included the following: baseline number of staff, baseline percentage of smokers, annual employee turnover rate, number of smokers interested in quitting, the cost of a smoking cessation program, expected success rate of a voluntary cessation program, smokers quitting spontaneously without a program, and employer-borne costs related to employee smoking. A variety of scenarios were constructed to generate a range of employer net economic impact figures and resulting percentages of smoking employees. Results showed that the benefits of a cessation program would be eliminated over several years, unless the prevalence of smoking in incoming employees was reduced. The most favorable scenario, combining a hospital cessation program and reduced smoking among new employees, generated cumulative savings, discounted at 5%, of $358,000 to $684,000 over an eight-year period.

Computer Simulation↗
PubMed1987

Effects of verapamil and converting enzyme inhibition on bilateral renal function of two-kidney, one-clip hypertensive rats.

Experiments were conducted in two-kidney, one-clip renal vascular hypertensive rats (GHR) to assess the responses of each kidney to acute treatment with the antihypertensive calcium channel blocking agent verapamil in the presence and in the absence of converting enzyme inhibitor (CEI). One group of GHR (0.2 mm inner diam. clip 3 weeks before study) were examined during a control period, and during a second period of infusion of verapamil (600 micrograms h-1 kg-1). A second group of GHR were examined during a control period, during CEI (teprotide, 3 mg h-1 kg-1) infusion and during a third period of verapamil (600 micrograms h-1 kg-1) infusion superimposed on CEI infusion. Although systemic blood pressure (BP) decreased from 175 +/- 4 to 149 +/- 5 mmHg (mean +/- SEM) in response to verapamil alone, renal blood flow for non-clipped kidneys increased from 5.9 +/- 0.4 to 6.5 +/- 0.3 ml/min, indicating a 30% reduction of renal vascular resistance (P values less than or equal to 0.01; n = 9). Glomerular filtration rate (GFR) for non-clipped kidneys (n = 24) increased from 0.91 +/- 0.09 to 1.47 +/- 0.14 ml/min and filtration fraction increased from 0.32 +/- 0.04 to 0.47 +/- 0.03 (P values less than or equal to 0.05). Urine flow rate and absolute and fractional sodium excretion for non-clipped kidneys increased. GFR for clipped kidneys decreased during verapamil. Treatment with CEI alone resulted in nearly identical responses of BP and function of the non-clipped kidney, except filtration fraction was unchanged. The addition of verapamil to ongoing converting enzyme blockade tended to augment the increased GFR of the non-clipped kidney. Plasma renin activity (PRA) increased from 30 +/- 3 to 59 +/- 7 ng of angiotensin (ANG) I h-1 ml-1 with verapamil alone, a significantly larger increment than the increase of PRA from 27 +/- 5 to 39 +/- 9 ng of ANG I h-1 ml-1 in GHR subjected to comparable blood pressure reduction by mechanical aortic constriction. Verapamil resulted in many similar effects on renal function to those observed during blockade of converting enzyme. The increased filtration fraction observed in response to verapamil may be the result of vasodilatation of the afferent arteriole or of an increase in the glomerular ultrafiltration coefficient.

Angiotensin II↗
PubMed1987

The epidemiology of the haemoglobin level--a study of 1057 subjects in general practice.

A prospective survey of the level of haemoglobin (Hb) has been carried out in 1057 subjects (607, 57.4% women) over the age of 40 randomly selected from the age-sex register of a North London group practice. Mean Hb levels were 15.04 +/- s.d. 1.41 g/dl in men and 13.54 +/- s.d. 1.32 g/dl in women (P less than 0.001). In men, Hb levels did not differ between the ethnic groups represented, but women of Mediterranean origin had significantly lower Hb levels than other women (P less than 0.001). There was no social class difference in Hb levels. Women under age 50 had significantly (P less than 0.001) lower Hb levels than older women. Smokers had significantly higher Hb levels than non-smokers (P less than 0.002) and there was a weak correlation with numbers of cigarettes smoked (men rs = 0.07, P = 0.07; women rs 0.14, P less than 0.001). Haemoglobin levels correlated with diastolic blood pressure in both men (r = 0.07, P less than 0.05) and women (r = 0.23, P less than 0.001). Thirty eight subjects (3.6%), 25 women and 13 men, were found to be anaemic (Hb less than 11.5 g/dl in women or less than 12.5 g/dl in men). Anaemia could be confirmed in only six of 19 subjects in whom repeat levels were measured. Screening for anaemia did not uncover any serious disease.

Adult↗
PubMed1987

Short-term effect of a 75 g oral glucose load on glycohaemoglobin levels.

Two hundred and twenty-three subjects out of a total of 347 with various degrees of glucose tolerance were recalled after a screening survey for diabetes. They were a randomly selected sample of people over the age of 40 and they underwent a formal 75 g glucose tolerance test in order to assess the effect of a glucose load on glycohaemoglobin levels measured by four different assay methods. Oral glucose loading was found to affect glycohaemoglobin levels only when these were measured by an agar-gel electrophoretic method that did not remove the labile aldimine-linked Schiff base fraction. The increase in glycohaemoglobin during the glucose tolerance test as estimated by this method was proportional to the 2 h blood glucose level. Glycohaemoglobin levels measured by agar-gel electrophoresis with elimination of the Schiff base, by affinity chromatography and by iso-electric focussing, were not affected by a 75 g oral glucose load. We conclude that blood samples for glycohaemoglobin assay may be collected at any time of the day, without regard to the subject's previous food intake, provided an assay method is used that removed the aldimine-linked labile fraction.

Adult↗
PubMed1987

Cerebellar glucose metabolism in chronic aphasia.

(18F)-Fluorodeoxyglucose PET was used to compare left/right cerebellar hemispheric glucose metabolism in 37 aphasic patients with left hemisphere lesions and 22 age-matched controls. Sixteen aphasic subjects showed cerebellar symmetry. Twenty-one aphasic subjects were found to have cerebellar metabolic asymmetry, which (1) resulted from an absolute reduction in local cerebral metabolic rates of glucose in the right cerebellar hemisphere; (2) was associated with left less than right glucose metabolic asymmetry in the frontal, parietal, caudate, and thalamic regions; (3) was associated with Broca's region and deep hemisphere structural damage to the internal capsule and basal ganglia; (4) related to reduced functional motor performance, spontaneous speech, naming, reading, and writing; and (5) included all Broca's aphasia subjects.

Aphasia↗
PubMed1987

Screening for diabetes mellitus in general practice using a reflectance meter system. The Islington Diabetes Survey.

The feasibility of using a blood-glucose reflectance meter to identify subjects with abnormal glucose tolerance in a community-based screening programme for diabetes mellitus has been assessed. 530 (51.0%) of 1,040 screened subjects had a finger-prick capillary blood-glucose level estimated 2 h after a 75 g oral glucose load. Blood-glucose estimations were performed on this sample by an automated glucose-oxidase method and by a reflectance meter system (Reflocheck, BCL (London) Ltd., Lewes, East Sussex, UK). Blood-glucose values measured by the meter were found to be higher than those assayed by the glucose-oxidase method by a mean ratio of 1.16:1. This overestimation could not wholly be explained by the meter being calibrated to measure plasma- rather than whole blood-glucose. This ratio was constant in specimens assayed by the glucose-oxidase method within 24 h of sampling or within 7 days of sampling. The meter system gave a good approximation of the prevalence of DM in the sample (14 "diabetics" identified by the meter, 15 by the glucose-oxidase 2hBG). The optimal test characteristics of the meter 2hBG as a screening test for DM were at a cut-off level of 9.7 mmol/l (sensitivity and specificity 98.4%, CI 85.8-100%, for sensitivity, 97.3-99.5% for specificity). However, in order to be 100% sensitive for DM, confirmatory GTTs would be necessary on all subjects with meter 2hBG greater than 9.5 mmol/l, providing a specificity of 98.2% (CI 97.0-99.7%). The unit cost of detecting 1 case of DM using a single meter became cheaper than using the laboratory glucose-oxidase method when 143 subjects had been screened.

Autoanalysis↗
PubMed1987

Screening for diabetic retinopathy--comparison of a nurse and a doctor with retinal photography.

The efficacy of diabetic retinal screening by a nurse trained in ophthalmoscopy and of a diabetologist was assessed by comparison with fundal photography. The study was performed in 282 subjects, 59 with known diabetes and 223 participating in a screening survey, of whom 13 had diabetes and 43 impaired glucose tolerance. The prevalence of retinopathy in the diabetic subjects was 36.8% and serious retinopathy 9.5% while in the screened subjects it was 3.5% and 0.9% respectively. The characteristics of nurse examination as a test to detect retinopathy was: sensitivity 50.0% +/- CL16.8%, specificity 99.2% +/- CL0.9%, which compared with 51.3% +/- CL15.7% and 98.7% +/- CL1.2% for the doctor. The nurse failed to detect serious retinopathy as accurately as the doctor, although new vessels were missed in 5 of 6 cases by the doctor. Screening for retinopathy requires either ophthalmoscopy by an observer trained to a higher level than is common in doctors, or non-mydriatic retinal photography.

Adult↗
PubMed1986

Staining of retinal neurons in the isolated eyecup by extracellular horseradish peroxidase injection.

A reliable method has been developed for the staining of mammalian retinal neurons in the isolated eyecup. Small injections of horseradish peroxidase are made at a number of places on the retinal surface while the hemisected eyecup preparation floats in Eagle's medium. After 30 min, the retinas are removed, fixed, and reacted with diaminobenzidine. Golgi-like staining of fine dendrites, spines and axons of ganglion cells is achieved. The method also stains amacrine, horizontal and bipolar cells.

Animals↗
PubMed1986

Arterial pressure and renal function in two-kidney, one clip Goldblatt hypertensive rats maintained on a high-salt intake.

Arterial blood pressure and renal function of both clipped and non-clipped kidneys of benign two-kidney, one clip (2K1C) Goldblatt hypertension were evaluated in order to determine whether high-salt intake alters the course of the development and magnitude of hypertension or influences renal function. The administration of 0.9% sodium chloride as a drinking solution for 3 weeks suppressed plasma renin activity (PRA) and kidney renin content of the clipped kidney to normal values. Despite suppression of PRA and kidney renin content, the saline-drinking clipped rats still developed hypertension of the same magnitude as the water-drinking clipped rats. However, the onset of hypertension was delayed by 4 days. Urine flow, glomerular filtration rate (GFR) and sodium excretion rate from the clipped kidneys of the saline-drinking clipped rats were higher than the corresponding values in the water-drinking rats, and approached those observed in control animals. Thus, the high-salt intake which was associated with suppression of the activity of the renin-angiotensin system delayed the onset of, but not the final magnitude of, the hypertension. In addition, kidney function in the clipped kidneys of saline-drinking clipped rats was enhanced compared with that observed in the water-drinking clipped rats.

Animals↗
PubMed1985

Nephron responses to converting enzyme inhibition in non-clipped kidney of Goldblatt hypertensive rat at normotensive pressures.

To evaluate the effects of angiotensin converting enzyme inhibition (SQ 20881, CEI) on superficial nephron function of the non-clipped kidney in Goldblatt hypertensive rats in the absence of alterations in renal arterial pressure, control renal arterial pressure (RAP) was reduced first to the range generally obtained during CEI (124 +/- 4 mm Hg). RAP was maintained during the CEI period by adjustment of a suprarenal aortic clamp. At the reduced RAP, whole kidney and single nephron glomerular filtration rates (GFR) were reduced from the hypertensive levels and were lower than the measurements in normotensive control rats. During CEI, whole kidney GFR and single nephron GFR increased by 55 and 42%, respectively. There were decreases in absolute as well as fractional proximal reabsorption rates. In the intermediate nephron segment, fractional reabsorption was decreased, but absolute fluid reabsorption increased in proportion to the increased delivery rate. Proximal tubule and peritubular capillary hydrostatic pressures increased significantly during CEI also. These results indicate that an increased activity of the renin-angiotensin system occurring in Goldblatt hypertensive rats subjected to aortic constriction exerts effects to lower GFR and increase proximal reabsorption rate. The concomitant superficial nephron and whole kidney GFR responses to CEI when arterial pressure was maintained suggests that the pre-existing levels of angiotensin exerted similar influences on the total nephron population.

Angiotensin II↗
PubMed1985

Use of ferrets in studies of the visual system.

The ferret (Mustela putorius furo) is proving to be an excellent experimental animal for many anatomical and physiological studies of the adult and developing visual system. As a result, the amount of data available on the ferret's visual system is increasing at a rapid rate. The purposes of this paper are to briefly review some of those data and to present some of the reasons why the ferret is an appropriate choice as an experimental animal for visual system studies.

Animals↗
PubMed1984

Near-normal glycaemic control does not correct abnormal platelet reactivity in diabetes mellitus.

The effect of improved glycaemic control, effected by 16 weeks continuous subcutaneous insulin infusion (CSII), on platelet aggregation and platelet prostaglandin biosynthesis has been assessed in a group of 11 diabetic patients with painful peripheral neuropathy. Before CSII and compared with results obtained on samples from age- and sex-matched control subjects, there was enhanced reactivity of the platelets from diabetic patients to ADP, collagen and sodium arachidonate (NaAA). There was also increased thromboxane B2 (TXB2) production after platelet stimulation by NaAA. In contrast, collagen-induced thromboxane production by platelets from diabetic patients was significantly less than that of platelets from controls. Treatment by CSII resulted in a statistically significant improvement in glycaemic control and this was maintained for the 16 week period of the study. At 16 weeks and in the presence of near-normal glycaemic control, the enhanced platelet reactivity in response to collagen and NaAA persisted and that to ADP was further increased. Collagen-induced thromboxane production was, however, corrected by CSII.

Adenosine Diphosphate↗
PubMed1983

Tritiated thymidine experiments in the cat: a description of techniques and experiments to define the time-course of radioactive thymidine availability.

Tritiated thymidine [(3H]thymidine) autoradiographic techniques have been used to define birthdates for cells in a variety of animals. In an effort to include [3H]thymidine experiments in our ongoing studies of visual system development, we have used an intrauterine injection procedure that affords [3H]thymidine labeling of dividing nerve cells in the cat. This report contains a detailed description of the injection procedures used, as well as the results of experiments undertaken to define the period of time during which the exogenous [3H]thymidine introduced by such injections remains available for uptake.

Animals↗
PubMed1982

A study of the stimulation of human venous prostacyclin synthesis by dipyridamole.

The synthesis of prostacyclin by human venous tissue in vitro and the effects of aspirin and dipyridamole thereon were investigated. Dipyridamole significantly stimulated prostacyclin production in a concentration range of 25 to 100 microM. Dipyridamole significantly attenuated the inhibitory effect of 0.1 mM aspirin in a concentration range of 12.5 to 100 microM. Isobutylmethylxanthine 0.1 mM, an unrelated inhibitor of phosphodiesterase, had similar effects to dipyridamole. Cyclic AMP 3.0 mM had an inhibitory effect on prostacyclin synthesis in the presence of dipyridamole. Adenosine 0.1 mM and nitrobenzylthioguanosine 0.1 mM, an inhibitor of adenosine uptake, did not significantly influence prostacyclin synthesis in this system. We conclude that the stimulation of prostacyclin synthesis by dipyridamole is unrelated to the ability of this drug to block the high-affinity uptake of adenosine by endothelial cells and that the effect may also be independent of changes in the concentration of cAMP induced by the drug.

Aspirin↗
PubMed1982

Low-dose aspirin inhibits platelet and venous cyclo-oxygenase in man.

In a group of normal subjects we have compared rates of recovery of venous prostacyclin (PGI2) and platelet thromboxane B2 (TXB2) production after a single 300 mg dose of aspirin. Marked inhibition of both venous PGI2 synthesis and platelet TXB2 synthesis persisted for the 72 hours duration of the study. We also examined the effect of four daily doses of 40 mg aspirin on platelet and vessel wall prostaglandin biosynthesis. This produced a cumulative inhibitory effect on TXB2 production with 98.6 per cent mean inhibition at 72 hours. At this time 81-100 per cent inhibition of PGI2 was demonstrated in the four subjects studied. We conclude that the cyclo-oxygenase enzyme in human vein is sensitive to inhibition by very low doses of aspirin. No evidence was found to substantiate the view that rapid recovery of vessel wall cyclo-oxygenase activity occurs after inhibition by a single dose of aspirin.

Aspirin↗
PubMed1982

Relationship between platelet aggregation, thromboxane synthesis and albumin concentration in nephrotic syndrome.

Increased platelet aggregability on stimulation with sodium arachidonate (NaAA), collagen and ADP was found in a group of 14 patients with nephrotic syndrome when compared with age and sex matched controls. Five of the group also exhibited spontaneous platelet aggregation (SPA), associated with synthesis of thromboxane B2 (TxB2), and which appeared to correlate with a markedly increased serum triglyceride concentration. Thromboxane B2 generation in response to NaAA was increased and reflected both the low serum albumin concentration and the platelet aggregation response to this agent. Addition of albumin in vitro decreased the amount of TxB2 generated for a given dose of NaAA and increased NaAA and collagen-induced platelet aggregation thresholds. However, albumin had no significant effect on collagen-induced TxB2 production. The results suggest that the hypoalbuminaemia and associated reduced binding of arachidonic acid and increased synthesis of TxA2 account in part for the increased platelet aggregability seen in the nephrotic syndrome but that other mechanisms are also involved.

Adenosine Diphosphate↗