Biomedical subjects
C R George
Publications and source records attributed to C R George.
Follicular aspiration: a comparison of an ultrasonic endovaginal transducer with fixed needle guide and other retrieval methods.
Ultrasonic techniques have been developed as alternatives to conventional laparoscopic aspiration for oocyte retrieval for in vitro fertilization (IVF). Given the advantages (less risk, lower cost, and greater patient acceptance) of these alternative techniques, it is appropriate to assess their efficacy compared with traditional laparoscopic retrieval. This article examines the recovery rate of oocytes and their subsequent fertilization rate with the use of an ultrasonic endovaginal transducer with fixed needle guide and compares these results with other retrieval methods. Comparisons were made between laparoscopic harvesting (n = 71, group I), ultrasonic transabdominal transvesical (n = 21, group II), and ultrasonic vaginal transducer (n = 76, group III). The data demonstrate comparable success using an ultrasonic endovaginal transducer with fixed needle guide. The authors believe this technique to be the procedure of choice for all routine oocyte retrievals during IVF treatment.
When is serum albumin worth measuring?
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The cause of rheumatic heart disease.
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Noninvasive testicular screening in childhood leukemia.
To evaluate the potential of transscrotal ultrasound and magnetic resonance imaging as noninvasive screening methods we studied 8 boys with acute lymphocytic leukemia before testicular biopsy. Ultrasonic images of the testes were performed in 4 patients, including 2 with negative and 2 with positive biopsies, and all images were interpreted as normal. Magnetic resonance images of the testes also were interpreted as normal in 4 patients, including 2 with negative and 2 with positive biopsies, and they were technically inadequate in the remaining 4. The results suggest that neither transscrotal ultrasonography nor magnetic resonance imaging as currently applied may substitute reliably for testicular biopsy as a screen for occult testicular leukemia.
Gated cardiac magnetic resonance structural imaging: optimization by electronic axial rotation.
Most magnetic resonance imaging has used body orthogonal axes with the Z axis placed along the length of the body and the X and Y axes at right angles to the body. This orientation is not optimum for the heart; visualization of sections along the short and long cardiac axes would best define cardiac structural detail and functional status. The new orientation was accomplished by selection of electronic angulation of the magnetic fields for each subject rather than by attempting to approximate the cardiac axes by altering the position of the patient. This technique improved visualization of comparative wall segments, valvular structures, and the true four-chamber view of the heart, and also gave the best visualization of the pericardium. In addition, more accurate estimates of chamber size and myocardial mass can be made from the short-axis orientation, since the sections are orthogonal to the myocardium.
Thoracic aortic dissections: magnetic resonance imaging.
Six patients with documented dissections of the thoracic aorta (two Type A, four Type B) were examined by magnetic resonance (MR) imaging using a 0.6-Tesla superconductive magnet. Cardiac gating was applied in five cases. Correlation was made with CT and angiography. MR imaging demonstrated the dissection in all six cases and accurately differentiated Type A from Type B dissections. Coronal and sagittal MR sections were advantageous in establishing the relationship of the three arch vessels to the dissection. In addition, cardiac-gated MR was useful in demonstrating mural thrombus and in distinguishing the true from the false lumen based on differences in signal intensity resulting from different flow rates. In five cases, the information obtained by MR was equal to or surpassed that obtained by CT. In the one case of a completely thrombosed dissection, the CT scan was more helpful. MR should become an important imaging modality in the evaluation of aortic dissections.
Nonurographic evaluation of renal calculous disease.
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Treatment of hemodialysis bone disease with 24,25-(OH)2D3 and 1,25-(OH)2D3 alone or in combination.
We studied the effects of vitamin D metabolites in 29 patients established on chronic hemodialysis. The patients were divided into four groups; one was treated with 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] 0.5 microgram/day, one with 24R,25-dihydroxyvitamin D3 [24,25-(OH)2D3] 10 micrograms/day, and one with both metabolites. The control group was not given vitamin D. Plasma levels of both metabolites were low before treatment. 1,25-(OH)2D3 levels became normal, and 24,25-(OH)2D3 increased to supranormal levels after administration of the corresponding metabolite. Combined treatment produced still higher plasma levels of 24,25-(OH)2D3, suggesting an interaction between the two metabolites. Patients receiving 1,25-(OH)2D3 alone had a greater increase in plasma calcium than those receiving both metabolites. In control patients, hyperparathyroid bone disease worsened over the 10-month observation period. 1,25-(OH)2D3 improved hyperparathyroid bone disease in most patients, as reflected by a reduction in osteoclast and osteoblast numbers, but had no demonstrable effect on mild osteomalacia. 24,25-(OH)2D3 had no significant effect on plasma biochemistry or bone histology, and the effect of combined treatment on histology was similar to that of 1,25-(OH)2D3 alone. Stainable bone aluminum increased slightly in patients given 1,25-(OH)2D3, but aluminum did not affect the response to treatment. We conclude that 1,25-(OH)2D3 is a useful agent in the treatment of renal bone disease, but no therapeutic role is apparent for 24,25-(OH)2D3.
Preoperative percutaneous transhepatic internal drainage in obstructive jaundice: a randomized, controlled trial examining renal function.
Thirty patients with obstructive jaundice with plasma bilirubin values greater than 200 mumol/L were randomized at the time of percutaneous transhepatic Cholangiography to undergo immediate or delayed surgery. The patients who had preoperative percutaneous transhepatic biliary drainage (PTBD) for 13.8 +/- 5.8 days had fewer surgical complications than did patients who underwent immediate surgery (p less than 0.02), although when the complications of PTBD were included this advantage was diminished. Immediate surgery caused greater deterioration of renal function as measured by plasma urea, plasma B 2-microglobulin, phosphate clearance, uric acid clearance, and maximal concentrating ability than occurred after PTBD or delayed surgery. The improvement in phosphate clearance that followed PTBD was sustained through delayed surgical treatment, indicating better tubular function in these patients. This article supports the concept that preoperative PTBD will reduce surgical morbidity and will result in less renal impairment than will immediate surgery. However, the morbidity rates of the PTBD procedure will preclude its wide use.
The pathogenesis of renal osteodystrophy: role of vitamin D, aluminium, parathyroid hormone, calcium and phosphorus.
Biochemical data and bone histology from 44 haemodialysis patients was compared using an histologic technique capable of evaluating separately the individual components of osteodystrophy. Hyperparathyroid bone disease was diagnosed by an elevated osteoclast count, and in advanced disease there was also fibrosis and woven bone. Osteomalacia, defined as an impairment in the rate of bone mineralisation, was present in two distinct forms: osteomalacia type I, characterised by wide osteoid seams, and osteomalacia type II, characterised by extensive thin, inactive osteoid. The histologic diagnoses were hyperparathyroid bone disease (15), osteomalacia type I (3), osteomalacia type II (6), hyperparathyroid bone disease and osteomalacia type I (12), hyperparathyroid bone disease and osteomalacia type II (6), normal (2). Aluminium was evident histochemically in 17 biopsies. Vitamin D metabolite levels were low in most patients and did not correlate with any biochemical or histological parameter. Parathyroid hormone levels were highly correlated with histological features of hyperparathyroid bone disease, and also correlated with plasma calcium, suggesting a degree of autonomy of parathyroid hormone secretion. Urea and creatinine were higher in the hyperparathyroid bone disease than the osteomalacia groups suggesting that poor dialysis contributes to the former. Statistical analysis showed that osteomalacia type I was associated with relatively low plasma calcium and phosphorus levels; osteomalacia type II was associated with increased bone aluminium and with the uraemic process itself, as reflected in the plasma creatinine level. This study shows relationships between renal osteodystrophy and plasma calcium and phosphorus levels, but no relationship with vitamin D metabolites. Aluminium appears to impair mineralisation even at relatively low levels of accumulation. However there are other unidentified factors associated with the uraemic process, contributing to all three components of renal osteodystrophy.
Magnetic resonance signal intensity patterns obtained from continuous and pulsatile flow models.
The purpose of this investigation was to extend previous steady state flow studies with magnetic resonance (MR) to pulsatile flow measurements obtained with gated cardiac techniques in man with a pulsatile artificial heart device. Bovine blood and a solution of MnCl2 were studied. Correlation was made with complex and time-varying MR signals observed in the descending aorta on cardiac gated images obtained through the midthorax. MR signals from flowing fluids represent velocity distribution as shown in a velocity profile, and laminar flow is distinguished from nonlaminar. At very slow flow rates, signal intensity is lower than background. As the rate is increased, paradoxical enhancement occurs followed by loss of signal, which is complete at 7 liters per minute with fluid and 15 liters per minute with blood. These areas correspond to maximum fluid velocities of 41 and 88 cm/sec, respectively.
Magnetic resonance imaging of renal transplants.
Nineteen patients were examined to determine the clinical potential of magnetic resonance imaging (MRI) for evaluation of renal transplants. A 0.6-T cryogenic magnet and spin-echo technique with varying pulsing factors were used. T1-weighted images were best for differentiating the cortical and medullary parts of the transplanted kidney. Of the six living-related transplants with good renal function that were imaged, five demonstrated good corticomedullary differentiation (CMD) and one faint CMD. Three transplants with acute rejection were imaged, and all demonstrated a decrease in CMD and decrease in overall signal intensity compared with baseline. No CMD was seen in the three chronically rejecting transplants imaged. The appearance of cadaveric transplants and acute tubular necrosis was quite variable. All perinephric fluid collections were well depicted by MRI. Lymphoceles could be distinguished from hematomas. MRI may prove to be a useful adjunct in the evaluation of renal transplants and perinephric fluid collections.
Feasibility of universal home haemodialysis with simplified techniques.
Maintenance haemodialysis was offered to an unselected series of patients presenting with end-stage renal disease between 1975 and 1982. Of the initial 283 patients, 274 started on haemodialysis, and 89% of these were alive and available for follow-up beyond the first 3 months of treatment. 98% of the latter eventually achieved permanent home haemodialysis with a system using simplified dialysis equipment and procedures, together with training methods designed to reinforce patient motivation. Universal home haemodialysis is now feasible when appropriate techniques are used.
Nuclear magnetic resonance (NMR) imaging in the evaluation of the liver: a preliminary experience.
To determine the usefulness of nuclear magnetic resonance (NMR) in evaluation of the liver, 19 examinations were performed. A variety of pathological conditions were examined, and correlation was obtained with computed tomography, ultrasound, and radionuclide liver/spleen scanning. Nuclear magnetic resonance was as sensitive as the correlating imaging modalities in the detection of focal disease. Parenchymal abnormalities could be detected only in hemochromatosis. Several patients with diffuse disease did demonstrate evidence of portal hypertension, but no characteristic findings were noted within the liver parenchyma. Our preliminary investigation did not include T1 and T2 values and it is hoped that these will allow greater diagnostic utility in the detection of diffuse parenchymal disease.
[3H] clonidine binding to rat hippocampal membranes.
Alpha adrenergic receptor subtypes in rat hippocampal membranes were studied, using [3H] clonidine as the radioactive ligand. On the basis of competitive binding studies, using the selective antagonist-prazosin, WB-4101, and yohimbine, [3H] clonidine appeared to bind to a population of presynaptic sites that are pharmacologically similar to receptors previously classified as alpha 2. A computerized model that linearized and produced the best possible fit to the experimental data points indicated that [3H] clonidine binds to a single population of receptors possessing equal affinity for the ligand. Binding data also indicated that rat hippo-campus contains significantly fewer [3H]clonidine binding sites than rat cortex.
Bone metabolism in chronic renal failure.
Quantitative bone histology was carried out on 37 haemodialysis patients. Hyperparathyroid bone disease (HPT) was diagnosed by an elevated osteoclast count, and high counts were associated with classic osteitis fibrosa. Osteomalacia (OM) was found in two distinct though frequently overlapping forms, both with increased osteoid surface. In classic OM (type 1), present in 19% of patients the osteoid seams were wide and the mineral apposition rate low, with the tetracycline bands wide and merging together. In the more common form of OM (type 2), present in 81%, the mineralising surface, as shown by tetracycline uptake, was reduced, but the mineral apposition rate was normal. Tetracycline surface was highly correlated with osteoblast surface, suggesting that osteoblasts play a role in mineralisation, and that type 2 OM is caused by a reduction in osteoblast surface. The osteoblast surface also correlated with serum parathyroid hormone, and so secondary hyperparathyroidism may obscure the diagnosis of type 2 OM, which may be almost universally present in haemodialysis patients. Type 1 OM is not obscured by secondary hyperparathyroidism. Of the 37 patients 5 had HPT, 9 OM and 22 HPT + OM. Only one had normal bone. Biochemical parameters had limited predictive value. The study also did not support the suggestion that endogenous calcitonin protects against HPT disease.