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Biomedical subjects

G D Robinson

Publications and source records attributed to G D Robinson.

At least 19 recordsLinked to original sources
PubMed2002

Assessment of agreement between general practitioners and radiologists as to whether a radiation exposure is justified.

The objective of this study was to assess agreement between General Practitioners (GPs) and Consultant Radiologists as to whether a radiation exposure is justified and whether a request conforms to the Royal College of Radiologists (RCR) guidelines. Three GPs and three Consultant Radiologists were asked to review 100 requests for plain film imaging from GPs and to state whether the request justified a radiation exposure and whether the request conformed to RCR guidelines. It was discovered that there is greater agreement between radiologists than between GPs; this is a consistent pattern. The best agreement was between two Consultant Radiologists using the RCR guidelines. The poorest was between GPs using the request form details. It is suggested that the guidelines should be symptom-based to improve efficacy.

England↗
PubMed1994

Characterization of trihalomethane (THM)-induced renal dysfunction in the rat. I: Effects of THM on glomerular filtration and renal concentrating ability.

Single non-lethal doses (3 mmol/kg) of chloroform (CHCl3), dichlorobromomethane (CHCl2Br), dibromochloromethane (CHClBr2), and bromoform (CHBr3) were administered by intraperitoneal injection to male Sprague-Dawley rats and glomerular filtration and renal concentrating ability were assessed at varied times (5-8 h, 21-24 h, and 45-58 h) following treatment. At this dose, each of the four trihalomethanes (THMs) elevated blood urea nitrogen (BUN) and reduced renal concentrating ability (as measured by H2O intake/output ratios, urinary total osmolality, and electrolyte levels). Three of the four THMs also significantly reduced glomerular filtration rate (GFR), with only CHCl3 failing to demonstrate an effect at 3 mmol/kg. In general, CHCl2Br demonstrated the greatest interference with these renal function parameters. The times of maximal THM-induced effect on BUN and glomerular filtration rate were observed to be 24 h and 21-24 h post-treatment, respectively. These data suggest that a single acute THM treatment can inhibit mammalian renal concentrating ability and glomerular filtration.

Animals↗
PubMed1994

Characterization of trihalomethane (THM)-induced renal dysfunction in the rat. II: Relative potency of THMs in promoting renal dysfunction.

Single non-lethal doses (3 mmol/kg) of chloroform (CHCl3), dichlorobromomethane (CHCl2Br), dibromochloromethane (CHClBr2), and bromoform (CHBr3) were administered by intraperitoneal injection to male Sprague-Dawley rats and proximal tubular secretion and reabsorption was assessed at varied times following treatment. Each of the trihalomethanes (THMs) at this dose inhibited proximal tubular secretion, as indicated by decreased in vitro renal cortical slice accumulation of organic anion p-aminohippuric acid (14C PAH). The time of maximal THM interference with 14C PAH uptake occurred at 8 h, with recovery being demonstrated by 48 h. Each of the THMs also demonstrated interference with tubular reabsorption, as assessed by urinary glucose excretion, with maximal interference occurring during the first day post-treatment and recovery being observed during the second day post-treatment. In each case, CHCl2Br was the most potent inhibitor of proximal tubular function. Combining these data with those of the preceding paper, the relative potency in disrupting renal function was, in general, CHCl2Br > CHCl3 > CHClBr2 > CHBR3. Since the time course of this investigation indicates that proximal tubular dysfunction precedes other THM-induced renal function interferences, it also appears that proximal tubular damage is the primary event leading to further manifestations of renal dysfunction.

Animals↗
PubMed1987

Neural and dietary modulation of proline-rich protein and 4 beta-galactosyltransferase biosynthesis in rat parotid glands.

Maintenance of rats on a bulk diet (50 per cent inert cellulose and 50 per cent laboratory chow) before or after the removal of the submandibular-sublingual glands resulted in hypertrophy of the parotid gland, and the induction of basic proline-rich proteins in that gland with apparent molecular weights similar to those found after chronic administration of isoproterenol. Surgical removal of either the sympathetic or parasympathetic nerve, or of both, impeded both gland hypertrophy and the gene expression for proline-rich protein in the denervated gland. Rats fed normal chow did not have induction of these proteins in the innervated control parotid nor in the denervated contralateral gland. The experimental regimen also showed in-vitro translation of mRNA with electrophoretic protein patterns similar to those with isoproterenol treatment. There was also increased synthesis of the enzyme 4 beta-galactosyltransferase (EC 2.4.1.38).

Animals↗
PubMed1986

Imaging of lymph node uptake after intravenous administration of indium-111 metalloporphyrins.

Indium-111- (111In) labeled tetra (N,N,N-trimethylanilinium) porphyrin (TTAP), tetra (N-methyl-4-pyridyl)porphyrin (TMPyP), and tetra(4-sulfonatophenyl)porphyrin (T4SPP) were synthesized and lymph node uptake was measured in animals after intravenous administration. In rats [111In] TTAP had maximum lymph node to muscle uptake ratios which averaged 85:1 between 24 and 48 hr postinjection. Total lymph node uptake was nearly 1% at that time. Lymph nodes in rabbits were clearly visualized by gamma scintigraphy at 48 hr after i.v. injection of labeled TTAP. These results suggest that 111In-labeled TTAP may be a prototype for the development of a class radiopharmaceuticals which permits visualization of lymph nodes after i.v. administration.

Animals↗
PubMed1985

Cerebral blood flow with the continuous infusion of oxygen-15-labeled water.

This work describes the determination of CBF in eight normal human subjects with positron emission tomographic (PET) imaging using the continuous intravenous infusion of H2(15)O. A whole-brain CBF model is described that permits the comparison of the CBF values determined using PET with those obtained using other methods. This model includes a correction for whole-brain recovery coefficient, a correction for the underestimation of flow due to the nonlinearity of the CBF model when considering tissue that includes both gray and white matter, the use of in vitro-determined brain-blood partition coefficients for gray and white matter, and a variation of the equilibrium model that permits the arterial concentration to vary. CBF values using this method compare well with values determined previously. Regional determinations using a brain overlay atlas are presented. Radiation dosimetry for the continuous infusion of H2(15)O is also included.

Adult↗
PubMed1984

Tandem Van de Graaff accelerator production of positron labeled radiopharmaceuticals for routine clinical use.

This paper describes a facility to produce positron labeled radiopharmaceuticals with a tandem Van de Graaff accelerator. 11C labeled carbon monoxide (11CO), 15O labeled H2O (H2 15O) and 18F labeled 2-deoxy-2-fluoro-D-glucose ([18F]2FDG), were chosen so that physiological measurements of cerebral blood volume, cerebral blood flow, and the cerebral metabolic rate for glucose could be made routinely in our PET center. This facility uses a tandem Van de Graaff accelerator which is relatively remote from the clinical area. Measurements of radionuclide yield and beam penetration showed that it was feasible to deliver sufficient amounts of radioactivity for the measurements. Both 11CO and H2 15O presented significant delivery problems due to their shorter half-lives. For H2 15O a continuous delivery system for water vapour and an infusion system for the administration of H2 15O in saline were designed and constructed. 11CO and [18F]2FDG were hand carried. This facility has demonstrated that a tandem Van de Graaff accelerator can routinely supply a PET center with adequate quantities of these three radiopharmaceuticals.

Carbon Monoxide↗
PubMed1982

[1-(11)C]palmitic acid: improved radiopharmaceutical preparation.

A simple synthetic procedure and processing system for the routine preparation of [1-(11)C]palmitic acid via carbonation of n-pentadecylmagnesium bromide with [11C]carbon dioxide is described. The key feature of this improved synthesis is the facile separation of the 11C fatty acid from the radiolabeled and unlabeled by-products of the Grignard reaction. Using this procedure and system 7.40-9.25 GBq (200-250 mCi) of [11C]CO2 was converted, after a synthesis time of 30 min, into 1.85-2.78 GBq (50-75 mCi) of pure, sterile, pyrogen-free [1-(11)C]palmitic acid suitable for human use with positron computed tomography.

Carbon Radioisotopes↗
PubMed1982

Tc-99m dextran: a new blood-pool-labeling agent for radionuclide angiocardiography.

We have explored the possibility of imaging the cardiac blood pool with dextran (Dx) labeled with Tc-99m (Tc) after Sn2+ reduction. Stannous dextran (SnDx) kits were prepared in advance and labeling was performed by adding Tc-99m. The labeling efficiency was greater than 95%. Technetium-99m dextran (TcDx) was highly stable both in vivo and in vitro. In seven dogs we compared the quality of blood-pool images obtained with TcDx of different molecular weights (4 X 10(4) = Dx-40; 5 X 10(5) = Dx-500; 2 X 10(6) = Dx-2000) and with Tc-99m red blood cells (TcRBC) labeled in vitro, and determined the organ distribution of this new agent by whole-body scanning and blood sampling. TcDx provided high-quality cardiac blood-pool images up to 60 min after injection. The heart-to-lung ratios averaged 3.7 for TcDx-40, 3.9 for TcDx-500, and 5.4 for TcRBC at 60 min. Whereas TcDx-40 showed a relatively rapid initial urinary excretion and TcDx-2000 was degraded rapidly, TcDx-500 demonstrated the best kinetics for blood-pool imaging. Thus, TcDx is a new radiopharmaceutical with high labeling efficiency and stability. It overcomes a number of the limitations of currently used blood-labeling agents and may become useful for blood-pool imaging in man.

Animals↗
PubMed1981

Remote, semiautomated production of F-18-labeled 2-deoxy-2-fluoro-D-glucose.

A routine production system for 2-deoxy-2-[18F]fluoro-D-glucose (2-18FDG) for medical use is presented. The method involves the preparation of F-18-labeled F2 by the 20Ne(d, alpha) 18F reaction, subsequent fluorination of 3,4,6-tri-o-acetyl-D-glucal, purification, and hydrolysis of the appropriate diastereoisomer to obtain 2-18FDG. These operations are performed using a completely remote, semiautomatic system. There have been no failures in more than 220 consecutive production runs. Currently, two preparations per day of 15-25 mCi of 2-18FDG are routinely performed, with a radiochemical purity, measured by TLC, in excess of 95% and with less than 1 mR radiation exposure to the chemist. Reaction conditions, operational variables, and systems are described in detail.

Deoxy Sugars↗
PubMed1977

Myocardial imaging with 123I-hexadecenoic acid.

123I-hexadecenoic acid is a terminally iodinated, 17-carbon fatty acid analog which is rapidly degraded in the myocardium. By determining regional myocardial distribution patterns and clearance rates, it may become useful as a single agent for estimating regional myocardial perfusion and for distinguished viable ischemic tissue from infarcted tissue. The high count rates obtainable with the iodine label permit acquisition of qualitative multiprojection images in only 3 min. per view, or quantifiable single projection high count images in 10 min. Ischemic defects may be observed in anginal patients without subjecting them to stress.

Adult↗
PubMed1977

Total and individual kidney function assessment with iodine-123 ortho-iodohippurate.

A simple and reliable method of preparing 123l o-iodohippurate (l-123 OIH) is described. The agent was used to evaluate renal function in 329 patients; its use results in significant dose reduction for those with obstruction, hypertension, or transplant. Images from l-123 OIH provide 2.4 times more detectable photons per mCi administered to the patient than images obtained from l-131 OIH. Diagnoses are expected to be more reliable with l-123 OIH due to the decreased random variation of each data point.

Adult↗
PubMed1977

Effects of hydration and physical therapy on tracheal transport velocity.

A new tracer method for quantitative measurement of tracheal transport velocity (mm per min) in dogs has been described. Using the same technique, the effects of dehydration, rehydration, postural drainage, and chest percussion on tracheal transport velocity were studied. Mean tracheal transport velocity decreased significantly (14.1 +/- 1.4) after dehydration (P less than 0.05) and reverted to normal (19.0 +/- 1.3) with rehydration in 10 dogs. After postural drainage in 7 dogs, mean tracheal transport velocity increased 39.7 +/- 1.78 (SE) per cent (P less than 0.01). After chest percussion in 6 dogs, mean tracheal transport velocity increased 50.9 +/- 1.22 (SE) per cent. With combined postural drainage and chest percussion, mean tracheal transport velocity increased 50.0 +/- 0.32 (SE) per cent. Although maximal improvement occurred after the combined therapy, the changes were not significantly different from those observed with each therapy alone. These therapeutic measures have been used empirically in the past. The present study gives some objective evidence for their beneficial effects in anesthetized dogs.

Animals↗