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G Jacobson

Publications and source records attributed to G Jacobson.

17 recordsLinked to original sources
PubMed1991

Treatment planning optimization using constrained simulated annealing.

A variation of simulated annealing optimization called 'constrained simulated annealing' is used with a simple annealing schedule to optimize beam weights and angles in radiation therapy treatment planning. Constrained simulated annealing is demonstrated using two contrasting objective functions which incorporate both biological response and dose-volume considerations. The first objective function maximizes the probability of a complication-free treatment (PCFT) by minimizing the normal tissue complications subject to the constraint that the entire target volume receives a prescribed minimum turmourcidal dose with a specified dose homogeneity. Probabilities of normal tissue complication are based on published normal tissue complication probability functions and computed from dose-volume histograms. The second objective function maximizes the isocentre dose subject to a set of customized normal tissue dose-volume and target volume dose homogeneity constraints (MVDL). Although the PCFT objective function gives consistently lower estimates of normal tissue complication probabilities, the ability to specify individualized dose-volume limits, and therefore the individualized probability of complication, for an individual organ makes the MDVL objective function more useful for treatment planning.

Esophageal Neoplasms↗
PubMed1990

Important parameters in semi-dry electrophoretic transfer.

The efficiency of semi-dry electrophoretic transfer after sodium dodecyl sulfate (SDS)-electrophoresis using PhastGel media was investigated in a model system using three isotope labelled proteins. To give a full picture of the blotting process the amount of protein present in the gel, membranes, and filter papers was determined after different transfer times. The influence of the transfer buffer, commonly used additives such as methanol and SDS, and several different immobilizing matrices was investigated. Soybean trypsin inhibitor, bovine serum albumin, and ferritin were used as model proteins to study the effect of size on transfer efficiency. Basically, all three stages of the blotting process decide the result; the elution of protein from the gel, the immobilization of protein to the membrane, and the loss of material from the membrane during transfer. A theoretical explanation for the observed poor binding to a second membrane is discussed. Our results show that the buffer composition has little influence on the efficiency of transfer from the gel, but can be significant to the binding capacity of the membrane. In all experiments performed, there was never one moment during the transfer when all protein was eluted from the gel and simultaneously still bound to the membrane. The highest recovery in the membrane was obtained at different time intervals for different proteins. This indicates that quantitative transfer procedures cannot be generalized. However, obtaining an optimal method for reliable quantification of a specific protein or group of proteins is possible. For general protein staining of nitrocellulose and polyvinylidene difluoride membranes, a highly sensitive silver staining method requiring only 15 min has been used.

Buffers↗
PubMed1979

Renal handling of beta-2-microglobulin, amylase and albumin in acute pancreatitis.

The renal handling of beta-2-microglobulin, amylase and albumin was studied in patients with acute pancreatitis. The data were compared with results obtained from patients with glomerular proteinuria and from patients with tubular proteinuria. Initially during acute pancreatitis, the clearance ratio (clearance protein/clearance creatinine) for beta-2-microglobulin was increased dramatically (77-fold) compared to normals. After four to seven days this ratio had fallen and was elevated only 7-fold. The corresponding figures for amylase were 3.3 and 1.8 times and for albumin 9 and 5 times respectively. In glomerular disease, the clearance ratios for beta-2-microglobulin, amylase and albumin were increased 6, 1.1, and 154 times and in tubular disease 448, 1.1, and 28 times, respectively. The electrophoretic pattern of the urinary proteins during pancreatitis was mostly normal. In a few cases, slight tubular proteinuria was noticed. Amylase activity in serum and urine from patients with pancreatitis was found to sediment, (S20,W = 4.6) in a sucrose gradient, identical to amylase from normal serum and urine. The marked increase in the excretion of beta-2-microglobulin probably reflects interference of the kidney function at the proximal tubular level. Determinations of this protein in urine may be of value in studies of kidney dysfunction that can accompany pancreatitis.

Acute Disease↗
PubMed1978

Human pituitary thyrotropin. Isolation of alpha and beta subunits by hydrophobic interaction chromatography.

Various conditions for the dissociation of highly purified human pituitary thyrotropin into subunits have been investigated. Dissociation on a preparative scale was accomplished by treatment with 1 M propionic acid at 32 degrees C for 16 h. The isolation of one alpha and two beta subunits was achieved by hydrophobic interaction chromatography on pentyl-Sepharose-4B. Radioimmunological technique was utilized to classify the subunits in accordance with current nomenclature and also to express their activities. The activities of the subunits overlapped insignificantly (less than or equal to 0.3%) and their content of intact thyrotropin was negligible (less than 0.05%). The characterization of the subunits included determination of their amino acid compositions. Analytical polyacrylamide gel electrophoresis of the subunits at acid and alkaline pH values revealed heterogeneity. By free-zone electrophoresis at alkaline pH it was possible to isolate four discrete iso-forms of both the alpha and the beta subunit. All these eight individual subunits had activities consistent with those of their immediate precursor fractions. Isolation of electrophoretically homogeneous thyrotropin subunits has not been reported previously.

Amino Acids↗
PubMed1978

Optimization of electrostatic imaging systems for minimum patient dose or minimum exposure in mammography.

The x-ray photon energies that give the highest signal-to-noise ratios per unit of exposure or average dose in mammography are significantly greater than those used in current film/screen systems. Optimum photon energies for detection of calcifications in a range of thicknesses of water and fat were calculated. Soft-tissue targets were also considered. Comparison of the theoretical results and those obtained experimentally with the Stanton mammography phantom indicate that operation at less than optimum photon energies is a major cause of inefficiency in film/screen mammography. On the other hand, electrostatic imaging systems, because of their processing flexibility, can operate at the optimum photon energy levels, thus minimizing either dose or exposure.

Elementary Particles↗
PubMed1978

Bilateral pleural thickening: a manifestation of asbestos dust exposure.

Bilateral pleural thickening in a relatively asymptomatic patient without evidence of pulmonary disease is frequently a manifestation of asbestos dust exposure, particularly when it is localized or in the form of a noncalcified pleural plaque. Bilateral pleural thickening will be discovered with increasing frequency if specifically searched for on every radiograph. This radiographic finding is suggested as a more realistic indication of asbestos dust exposure, particularly when correlated with a complete occupational history.

Asbestos↗
PubMed1977

Fetal malnutrition: an appraisal of correlated factors.

Fetal malnutrition has emerged as a significant health problem over the past decade. Present evidence suggests that maternal environment plays the major etiologic role in fetal malnutrition. The association of fetal malnutrition in mothers with chronic hypertension is well known, but fetal malnutrition is associated with maternal hypertension in less than 25 per cent of cases. Among a group of 182 pregnant women studied at midpregnancy for blood levels of vitamins, trace metals, proteins, amino acids, and parameters of maternal leukocyte energy metabolism, it was found that the concentration of 10 amino acids, alpha-1-globulin, zinc, and total carotenes had a statistically significant relationship to fetal growth. Similarly significant correlations were found for maternal leukocyte adenosine disphosphate, phosphofructokinase activity, ribonucleic acid (RNA) synthesis, and cell size. Maternal cigarette smoking was correlated with reduced fetal growth. Analysis showed that there was a significant reduction in leukocyte RNA synthesis and phosphokinase activity and in the plasma levels of 14 amino acids, and carotene in smoking mothers. This information lends support to the hypothesis that factors which affect the growth of fetal cells also will affect maternal leukocytes in a definable way.

Adolescent↗
PubMed1977

Human pituitary thyrotropin. Characterization of five glycoproteins with thyrotropin activity.

Human pituitary thyrotropin prepared by chromatography on hydroxyapatite or on SP-Sephadex was fractionated into five active components by preparative poly-acrylamide gel electrophoresis. The potency of the five components was 4-9 units human Research Standard A/mg. Examination of the components by analytical electrophoresis and by immunological methods revealed no heterogeneity. Ultracentrifugaiton of the three major components showed homogeneity with sedimentaiton coefficinets in the range of 2.4-3.0 S and a value for the molecular weight of about 33 000. Amino acid and carbohydrate analyses indicated close similarites between the five components.

Amino Acids↗
PubMed1977

Preliminary studies using electron radiography for mammography.

An electron radiography mammography system was used for phantom studies and to obtain 230 craniocaudal view patient studies, of which 140 were compared to xeroradiographs for their ability to visualize 7 features of diagnostic importance. The average exposure of the electron radiographs was 89 mR. The technique was considered equal or superior to xeroradiography in 58% of the compared diagnostic features, while patient dose was reduced.

Breast Neoplasms↗
PubMed1976

Significance of irregular small opacities in radiographs of coalminers in the USA.

The purpose of this study was to determine the factors that are associated with the occurrence of small irregular opacities in the chest radiographs of coalminers, and whether the lung function of miners with irregular opacities differed from that of miners with small rounded opacities, a mixture of small rounded and irregular opacities, or an absence of opacities. A subsample of 6166 coalminers was selected from 9076 miners who had been examined by the US Public Health Service as part of the National Study of Coalworkers' Pneumoconiosis. The subsample consisted of 4479 smokers and 1687 non-smokers. The chest radiograph of each miner was classified according to the UICC/Cincinnati Classification.

Adult↗
PubMed1976

Electronic grids for electrostatic imaging systems.

Electronic grids have been substituted for conventional grids in an electrostatic imaging system and have been useful in chest radiography. Electronic grids also appear to be useful for clean-up of small amounts of scattered radiation in radiographs of the extremities. More clinical work is needed before a statement about the use of electronic grids for other examinations can be made.

Electronics, Medical↗
PubMed1975

Isolation of five active thyrotropin components from human pituitary gland.

A procedure is described for the isolation of human pituitary thyroid-stimulating hormone (thyrotropin). The starting material was a side-fraction provided by the earlier developed process for the purification of growth hormone from whole frozen pituitaries. This fraction was further purified by successive chromatography on Bio-Gel P-150, Bio-Gel HT hydroxyapatite, and SP-Sephadex C-50. The resulting preparation was obtained in yields of 10 mg/kg of pituitary tissue and had a thyrotropin potency of 11 units human Research Standard A/mg as measured by a specific radioimmunoassay. Contamination by other pituitary hormone activities was low. In the ultracentrifuge a single sedimenting boundary was registered with an s20,w value of 2.7 S. The molecular weight as determined by sedimentation-equilibrium experiments was 34 000 in phosphate buffer, pH 7.0, and 17 700 in 1 M propionic acid. This thyrotropin preparation was, however, electrophoretically heterogenous. Following preparative polyacrylamide gel electrophoresis five different components associated with thyrotropin activity were isolated. Isolation on a preparative scale of electrophoretically homogeneous human thyrotropin has not earlier been reported. One of the thyrotropin components was characterized with respect to molecular weight and amino acid composition. The data were consistent with a molecular weight of 33 000 from sedimentation-equilibrium analysis at pH 7 and with 268 amino acid residues per molecule.

Amino Acids↗
PubMed1975

Viewbox seminar: a new method for teaching roentgenology.

The American College of Radiology designed a "crash" program to train radiologists to interpret and classify the radiological manifestations of coal workers' pneumoconiosis. This Viewbox Seminar combines two pedagogic techniques, group viewbox study, and a test-teach-test sequence of instruction that compels active participation in the learning process. Weekend scheduling and good location and transportation connections facilitate attendance, making this an excellent way to teach large groups of radiologists certain subtleties of radiology in a short time.

Audiovisual Aids↗