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Biomedical subjects

D R Robertson

Publications and source records attributed to D R Robertson.

At least 37 records · Page 2Linked to original sources
PubMed1992

Raised blood urea in the elderly: a clinical and pathological study.

We have attempted to define a normal range for blood urea and creatinine for elderly inpatients and to determine the relative importance of pre-renal, renal and post-renal pathology in those with renal impairment. A total of 118 admissions to an acute geriatric unit and 67 separate post mortems in patients over 67 years of age were studied prospectively. Up to 123 items of data were coded and analysed including blood urea and creatinine, clinical or pathological changes associated with renal disease, clinical outcome and post mortem findings. We determined our own 'normal' hospital ranges for urea (1.4-13.2 mmol/l) and creatinine (48-141 mumol/l) from plasma values in 76 patients with no evidence of renal impairment, either on admission or in the past. Using these values 41% of post mortem cases and 25% of clinical admissions had a raised blood urea. Pre-renal conditions such as cardiac failure, dehydration and gastrointestinal haemorrhage, either alone or in combination, were present in 56% of these patients. Urea and creatinine values were substantially higher in patients who died in hospital as opposed to those who were discharged or transferred. Creatinine values were greater in those with intrinsic renal disease or post-renal obstruction as compared to patients with pre-renal causes of renal impairment. Patients with histological evidence of extensive glomerulosclerosis or nephrosclerosis had higher urea and creatinine levels than those with only minor ageing changes.

Aged↗
PubMed1991

The influence of protein containing meals on the pharmacokinetics of levodopa in healthy volunteers.

1. The pharmacokinetics of levodopa and paracetamol after single oral doses have been investigated in eight healthy young volunteers in the fasted state and following isocaloric meals containing either 10.5 g or 30.5 g of protein. 2. The initial peak and maximum plasma drug concentrations and the times at which these occurred were not affected by food. 3. The mean area under the plasma concentration-time curve (AUC) for paracetamol following an overnight fast did not differ significantly from that observed following the low and high protein meals. 4. By contrast, the AUC for levodopa following the low protein meal (193.9 +/- 15.7 micrograms ml-1 min) was significantly lower compared with administration in the fasted state (216.5 +/- 26.1 micrograms ml-1 min). However, there were no significant differences in the kinetics of levodopa between the fasting state and following the high protein meal. 5. There was no evidence that consumption of a meal containing 30.5 g of protein impaired either the rate or extent of absorption of levodopa. Therefore the reported beneficial effects of a low protein diet in the treatment of patients with Parkinson's disease probably result from reduced competition for levodopa transport across the blood-brain barrier.

Acetaminophen↗
PubMed1990

Three-dimensional image display in medicine.

This article is a tutorial on the methods used to create three-dimensional (3-D) images for use in displaying patient anatomy. This new view into anatomy has developed over the last 10 years from the need of surgeons, radiation therapists, and radiologists to integrate the many images resulting from the recent growth in tomographic imaging including computed tomography (CT) and magnetic resonance imaging (MRI). CT and MRI studies result in 30 to 100 images. 3-D imaging processes and integrates this image data volume and extracts more meaningful, derivative images via multiplanar reconstruction (MPR), shaded surface processing, or volumetric processing. MPR reslices the image volume to produce novel views of patient anatomy while retaining the image voxel intensities. Realistic shaded surface display of 3-D objects can involve extensive processing of the images to create computer representations of objects rendered into a displayable 3-D scene. Volumetric imaging combines the voxel processing of MPR with the techniques of tissue classification and surface shading to produce novel projections of the image data volume that allow automated creation of 3-D scenes without recourse to the complexities of object delineation. As the ultimate 3-D display, recent advances in computer-aided design (CAD) and computer-aided manufacturing (CAM) allow the fabrication of physical models of anatomy using computer-controlled milling machines. New technology that actually builds the model layer by layer from a liquid plastic offers the possibility of complete models with intact internal anatomy. The growth in 3-D is certain as hardware and software costs decrease and medical professionals find further applications for this technology.

Humans↗
PubMed1990

Treatment of post herpetic neuralgia in the elderly.

The incidence of acute herpes zoster and post herpetic neuralgia (PHN) increases with age. PHN resolves spontaneously within three months in approximately 50% of cases, although 22% experience discomfort for more than a year. There is little good evidence that treatment with antiviral agents, corticosteroids, local and regional anaesthesia, amantadine or levodopa in the acute stage can prevent the development of PHN. However, few studies have sufficient statistical power to allow firm conclusions to be drawn. Amitriptyline is beneficial in patients with established PHN and has an analgesic effect which is independent of its antidepressant action. Anticonvulsants and neuroleptics are of unproven efficacy and should be avoided in the elderly as side effects are common. Various local anaesthetic and surgical techniques may provide temporary relief in individual patients although none has been shown to produce consistent benefit. Transcutaneous electrical nerve stimulation (TENS) is free from adverse effects and appears to benefit some patients. Intractable pain often results in over-prescribing with the risk of adverse drug reactions. Drug therapy should be minimized with careful assessment of the risk/benefit ratio for any additional medication.

Adrenal Cortex Hormones↗
PubMed1990

Drug therapy for Parkinson's disease in the elderly.

The diagnosis and management of Parkinson's disease in the elderly is complicated by the common presence of multiple pathology and age related changes in drug handling. Accurate diagnosis requires a high index of suspicion combined with careful assessment before and after a trial of therapy. A multidisciplinary approach is required to help the patient, and their carer, cope with the fundamental disabilities resulting from Parkinson's disease. The elderly are more susceptible to side effects from antiparkinsonian medication and close supervision is therefore essential.

Aged↗
PubMed1990

The influence of levodopa on gastric emptying in man.

1. Simultaneous radioisotopic (99Tc-DTPA) gastric emptying measurements and paracetamol pharmacokinetic studies were performed in eight healthy male volunteers with and without levodopa (125 mg orally). 2. In the absence of levodopa gamma camera imaging showed rapid mono or biexponential emptying in all subjects and the plasma concentration-time curves for paracetamol displayed a single major peak. 3. In the presence of levodopa the time to 90% emptying was prolonged from 32 +/- 24 min to 81 +/- 20 min (P less than 0.01). Gastric emptying was interrupted by a plateau phase in six subjects and this pattern of emptying was associated with double peaks in the plasma concentration-time curves of both levodopa and paracetamol. The time to the end of the plateau phase of emptying correlated with the time to the trough plasma concentrations of paracetamol and levodopa. 4. There was excellent agreement between the plasma concentration-time curves of levodopa and paracetamol, i.e. time to initial peak, r = 0.946, P less than 0.001; time to trough concentration r = 0.943, P less than 0.01; time to second peak r = 0.974, P less than 0.001. 5. The results indicate that levodopa inhibits gastric emptying and thus influences its own absorption. Temporary inhibition of gastric emptying by levodopa (or a metabolite) is the cause of the multiple plasma peaks commonly observed following oral levodopa.

Acetaminophen↗
PubMed1990

Orthopaedic geriatric care--is it effective? A prospective population-based comparison of outcome in fractured neck of femur.

Orthopaedic geriatric care has become widely accepted despite relatively little formal evaluation. In the East Dorset health authority all patients with fractured neck of femur initially share common orthopaedic facilities but only those from one geographical sector have subsequent access to an orthopaedic geriatric unit, patients from the other sector receiving standard care. We have carried out a prospective population-based comparison of the outcome of 155 consecutive incident cases of fractured neck of femur aged over 65 years. On admission to hospital the two populations were similar in respect of age, sex, fracture type, social status, medical and orthopaedic problems, mental status and dependency (Clifton assessment procedure for the elderly). Multiple regression analysis showed that the mean length of stay was 9.5 days shorter in patients from the sector with access to orthopaedic geriatric care (p less than 0.05, 95% confidence interval 0.6 to 18.4 days). This reduction was not due to any difference between the two groups as regards dependency or the level of support provided on discharge. There was no difference in outcome at 6 months post-operatively in terms of mortality, functional outcome (pain and mobility), change in dependency or social status. We conclude that in the East Dorset health authority this combined approach has resulted in a significant reduction in the length of inpatient stay without any other apparent effect on patient outcome.

Age Factors↗
PubMed1989

The effect of age on the pharmacokinetics of levodopa administered alone and in the presence of carbidopa.

1. The effect of age on the pharmacokinetics of levodopa administered alone and in the presence of carbidopa was investigated in young and elderly healthy volunteers. 2. The plasma clearance of levodopa following intravenous administration of 50 mg was 14.2 +/- 2.8 (s.d.) ml min-1 kg-1 in the elderly compared with 23.4 +/- 4.1 ml min-1 kg-1 in the young (P less than 0.01) which resulted in a 49% greater area under the plasma concentration-time curve (AUC) in the older subjects (P less than 0.01). The volume of distribution (Vss) was lower in the elderly (1.01 +/- 0.29 l kg-1) than in the young (1.65 +/- 0.39 l kg-1) (P less than 0.002). 3. Following oral administration of 250 mg of levodopa the AUC was 2512 +/- 588 ng ml-1h in the elderly compared with 1056 +/- 282 ng ml-1h in the young (P less than 0.002). Cmax was also significantly greater in the elderly (P less than 0.05). The bioavailability of levodopa was significantly greater in the elderly (0.63 +/- 0.12 compared with 0.41 +/- 0.16, P less than 0.01). 4. In the presence of carbidopa, the plasma clearance of intravenous levodopa (50 mg) was reduced in both age groups but remained lower in the elderly (5.8 +/- 0.9 ml min-1 kg-1 compared with 9.3 +/- 1.0 ml min-1 kg-1; P less than 0.01). This resulted in a 54% greater AUC in the older subjects (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1989

Effects of an external resistance on maximum flow in chronic obstructive lung disease: implications for recognition of coincident upper airway obstruction.

To determine how the presence of generalised airflow limitation due to chronic obstructive lung disease affects the recognition of simulated upper airway obstruction, a study was carried out in 12 patients (mean (SD) age 57 (7) years) with chronic obstructive lung disease (FEV1% predicted 53 (22), range 21-70) and 12 matched control subjects. Patients and control subjects performed maximal inspiratory and expiratory flow-volume curves in a variable volume plethysmograph with and without upper airway obstruction simulated at the mouth with a series of polythene washers of internal diameter 4, 6, 8, 10, and 12 mm. In patients, as in normal subjects, peak expiratory flow (PEF) and maximum inspiratory flow at 50% of vital capacity (Vmax50) were more sensitive to upper airway obstruction than were FEV1 or maximum expiratory flow at 50% VC (VEmax50); but the reductions in all indices caused by simulated upper airway obstruction were smaller in the patients than in the controls. The fall in PEF (whether expressed in absolute units or as a percentages) consequent on severe (4 mm) upper airway obstruction became smaller with increasing severity of chronic obstructive lung disease. The subjects also produced flow-volume curves with and without 6 mm upper airway obstruction while breathing helium and oxygen (heliox). In both groups the effects of heliox on PEF and Vmax50 were increased when upper airway obstruction was simulated. It was confirmed that the functional recognition of upper airway obstruction is more difficult in patients with chronic obstructive lung disease than in normal subjects and this difficulty increases with severity of disease; an unusually large increase in PEF or Vmax50 while the patient is breathing heliox should raise the suspicion of coexisting upper airway obstruction, but such a pattern is not specific.

Aged↗
PubMed1988

Immunohistochemical and morphometric analysis of calcitonin distribution in anuran ultimobranchial glands.

The presence and distribution of immunoreactive calcitonin (iCT) in the anuran (Rana pipiens) ultimobranchial gland was examined with a specific antiserum to salmon calcitonin. Improved resolution of the distribution of iCT within individual cells allowed recognition of a iCT-negative [iCT(-)] early maturing cell, the primary iCT-positive [iCT-(+)] secretory cell with accumulation of iCT within the basal and apical cytoplasm, an iCT(-) cell that lacks a basal accumulation of secretory material, and a iCT(-) cell that borders the central lumen. A morphometric analysis was made of the entire glandular basal secretory surface area and a calculation was made of the relative area that contained iCT(+) secretory material (expressed as a basal index (BI)). For frogs kept in fresh water, the total basal area of a single gland was 0.335 mm2, with a BI of 0.72 and a total iCT(+) secretory surface of 0.241 mm2. A second group of frogs kept in a high calcium medium for 12 days had a BI of 0.74 with no significant increase in parenchyma volume or total basal area and therefore no increase in the total iCT(+) secretory area. A third group was kept in a high calcium medium for 12 days and given a single oral dose of vitamin D3 (500 IU/g body wt). The BI of this group remained unchanged at 0.75; however, there was a significant glandular hypertrophy concomitant with an increase in secretory surface area to 0.462 mm2. This resulted in a 43% increase in the iCT(+) secretory area to 0.345 mm2. A model is proposed to explain the increase in iCT in the gland in response to a vitamin D and high calcium challenge.

Animals↗
PubMed1988

Age-related changes in the pharmacokinetics and pharmacodynamics of nifedipine.

1. The effects of age on the pharmacology of nifedipine were investigated in 11 young and six elderly normotensive volunteers. 2. Following 2.5 mg of nifedipine i.v. the plasma clearance of nifedipine was 348 +/- 83 (s.d.) ml min-1 in the elderly compared with 519 +/- 125 ml min-1 in the young (P less than 0.05) and the AUC in the elderly was significantly greater at 125 +/- 28 ng ml-1 h compared with 83.9 +/- 19 ng ml-1 h (P less than 0.05). The Vss was similar in both age groups. 3. Following 10 mg oral sustained release nifedipine the AUC was 281 +/- 64 ng ml-1 h in the elderly compared with 136 +/- 56 ng ml-1 h in the young (P less than 0.002) and Cmax in the elderly was significantly greater at 36.8 +/- 11.8 ng ml-1 compared with 22.3 +/- 5.8 ng ml-1 (P less than 0.05). The trend towards an increased bioavailability in elderly subjects (36%) was supported by a significantly lower nitropyridine metabolite/nifedipine ratio in the elderly. 4. Absorption rate limited kinetics of the sustained release formulation were indicated by the prolonged t1/2 compared with i.v. administration. In the elderly t1/2 (oral) was significantly greater than in the young (elderly 6.7 +/- 2.2 h, young 3.8 +/- 1.4 h, P less than 0.05). 5. Haemodynamic changes in the young were confined to a tachycardia following i.v. administration. In the elderly, supine BP fell significantly following both oral and i.v. nifedipine while the heart rate remained unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1988

The pharmacokinetics of oral nifedipine--a population study.

1. The pharmacokinetics and metabolism of nifedipine have been studied in a population of 59 young male volunteers following administration of a 10 mg capsule. 2. The area under the plasma concentration-time curves (AUC) for nifedipine demonstrated a skewed but not a bimodal distribution (mean 154 ng ml-1 h; range 54-306 ng ml-1h). 3. Calculation of the ratio of the AUC of nifedipine to the AUC of its nitropyridine metabolite did not separate those individuals with high AUC values of nifedipine from the remainder of the population. 4. Similarly there was no evidence for bimodality in the excretion of the major urinary metabolite. Those subjects with high plasma AUC values for nifedipine excreted similar amounts to the remainder of the population. 5. In contrast to a previous study using a 20 mg oral dose, there was no evidence of polymorphism in the pharmacokinetics or metabolism of nifedipine following a single 10 mg oral dose.

Administration, Oral↗
PubMed1987

Sympathetic preganglionic neurons in frog spinal cord.

Sympathetic preganglionic neurons innervating the first sympathetic ganglion were identified in a frog (Rana pipiens). After wheat germ agglutinin conjugated horseradish peroxidase was implanted into this ganglion a homogeneous population of labeled sympathetic preganglionic neurones were identified ipsilaterally within the lateral field of the spinal gray at the level of the third spinal nerve. The total population of labeled cells (n = 324 +/- 62) extended in a rostrocaudal field for about 1800 micron as two distinct columns consisting of about equal numbers of cells. One group, at the lateral border of the intermediate zone, corresponds to the intermediolateral column, as also found in mammals, while the second group extends within the intercalated region, as the intercalated nucleus, lateral and slightly dorsal to the central canal. Transection of spinal nerves reveals that 65% of preganglionic axons leave the cord from the third spinal nerve with the remainder coursing through the first and second spinal nerves.

Adrenergic Fibers↗
PubMed1987

Plasma immunoreactive calcitonin in the frog (Rana pipiens).

1. Plasma immunoreactive calcitonin (iCT) and ionic calcium [( Ca]i) were measured in intact frogs (Rana pipiens) within complete 24 hr light-dark cycles over an 18 month period. 2. Plasma iCT exhibits an annual periodicity about the annual mean of 10.0 ng/ml, with an amplitude of 5.4 ng/ml that peaks in October. 3. Within an annual cycle, a significant inverse association exists between the basal monthly levels of plasma iCT and [Ca]i for animals maintained in freshwater control conditions. 4. When subjected to a high calcium environment during the latter half of the year, plasma [Ca]i and iCT were elevated above control levels but exhibited independent cyclic patterns. 5. A distinct seasonal response of increased iCT in a high calcium environment may be related to the secretory activity of the ultimobranchial glands and physiological responsiveness to other calcemic hormones; e.g. parathyroid hormone and vitamin D.

Animals↗
PubMed1986

Autonomic and sensory innervation of anuran ultimobranchial glands: a horseradish peroxidase study.

The extrinsic innervation of the endocrine ultimobranchial glands in the frog were identified by retrograde labeling with horseradish peroxidase. Labeled neurons were seen ipsilateral to the side injected in the caudal region of the vagal motor nucleus, the jugular sensory ganglion and first and second cervical sympathetic ganglia. These studies demonstrate a dual autonomic and vagal sensory innervation of the gland that are compatible with previous ultrastructural studies, but indicate a more complex innervation than previously shown.

Animals↗
PubMed1985

Annual and diurnal patterns of plasma calcium fractions in anuran Rana pipiens.

Ionized calcium [Ca2+] in the amphibian Rana pipiens was measured over 18 mo. An annual variation about the mean of 1.10 mmol/l was observed that peaked in April (1.36 mmol/l) and attained minimal levels in October (0.84 mmol/l). Plasma total calcium [Ca]t, plasma proteins, and the bound calcium fraction also exhibited annual oscillations. The annual mean binding capacity of plasma proteins for calcium was established at 0.0175 mmol/g. Of the plasma total calcium in spring animals, nonprotein-bound calcium complexes [Ca]c were less than 3% of the total whereas 80% was composed of [Ca2+] and 17% as protein-bound calcium [Ca]pb. In autumn [Ca2+] composed 40%, [Ca]pb 30%, and [Ca]c 30% of plasma total calcium. An equilibrium exists between [Ca2+] and [Ca]c, which maintains a combined annual mean of 1.48 mmol/l calcium. Diurnal variations superimposed on the annual cycles are modulated by apparent movement of plasma water and an intrinsic 12-h rhythm for [Ca2+]. No definite associations could be made with the entrainment of specific rhythms of the three calcium fractions with the light-dark cycle.

Animals↗
PubMed1984

Prospective comparison of three non-invasive tests for pancreatic disease.

Ultrasonography, computed tomography (CT), and an oral pancreatic function test were evaluated prospectively in 107 consecutive patients suspected of having pancreatic disease, the final diagnosis being made independently of these tests. Seventeen patients proved to have either chronic pancreatitis or a pancreatic neoplasm. Five had an unfused ventral pancreas and 10 had "minimal change" pancreatograms. Seventy five patients did not have pancreatic disease. Among the 17 patients with pancreatic disease the sensitivities of ultrasound, CT, and the pancreatic function test were 70%, 71%, and 76% respectively; among those without disease values of specificity of the three tests were 75%, 87%, and 72%. All three tests failed to detect most of the patients with unfused ventral pancreases or minimal change pancreatograms. The predictive values of a positive result for the three tests were 43%, 67%, and 34%. The predictive value of a negative result was greater than 90% for all the tests. Results improved when CT was combined with either of the two other tests. These findings show that CT is the most accurate of the three tests in diagnosing pancreatic disease but that a combination of ultrasound and the oral pancreatic function test offers a more widely applicable and almost as accurate alternative.

4-Aminobenzoic Acid↗