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Biomedical subjects

S M Larson

Publications and source records attributed to S M Larson.

At least 271 records · Page 15Linked to original sources
PubMed1979

Radiometric measurement of differential metabolism of fatty acids by Mycobacterium lepraemurium.

An assay system has been developed based on automated radiometric quantification of 14CO2 produced through oxidation of (1--14C) fatty acids by mycobacteria. With this system, the Hawaiian strain of M. lepraemurium was studied using the K-36 buffer as a suspending solution for the organisms along with 5.0 muCi of one of the following fatty acids: acetate, butyric, hexanoic, octanoic, decanoic, lauric, myristic, palmitic, stearic, oleic, linoleic, linolenic, and malonic. The 14CO2 production by this organism was greatest with lauric, decanoic, myristic, octanoic, stearic, oleic, linoleic, linolenic, and malonic. The 14CO2 production by this organism was greatest with lauric, decanoic, myristic, octanoic, and stearic acids, in decreasing order. Assimilation studies and radiochromatograms confirmed that most of the oxidized substrates were converted into by-products with no change in those from which no oxidation was found. These data suggest that the radiometric measurement of differential fatty acid metabolism may provide a basis of radiometric identification of M. lepraemurium and assessment of the growth requirements of this organism.

Carbon Dioxide↗
PubMed1979

A transferrin-mediated uptake of gallium-67 by EMT-6 sarcoma. I. Studies in tissue culture.

We have studied the in vitro uptake of gallium-67 by exponentially growing EMT-6 sarcoma cells in long-term tissue culture. In this system, the addition of transferrin to the medium was required before an appreciable cellular uptake of Ga-67 occurred. The transferrin effect was complex, with an initial stimulation to a peak cell-to-medium ratio of 8--10:1 at low concentrations of transferrin (0.2 mg/ml), followed by a gradual decline in uptake as transferrin in the medium was increased further. EMT-6 tumor-cell uptake of Ga-67 was probably mediated by a specific cellular receptor for transferrin. Scatchard analysis of the EMT-6 cellular binding of human transferrin labeled with iodine-125 indicated a cellular receptor with affinity for transferrin of 5 X 10(6) l/mole and abundance of 500,000 receptors per cell. Over the experimental range of transferrin concentration in the medium, the observed uptake of Ga-67 was closely correlated with the degree of formation of Ga-67-labeled transferrin and the fraction of transferrin bound to the cellular receptor (N = 69, r = 0.86, p less than 0.0001).

Animals↗
PubMed1979

A transferrin-mediated uptake of gallium-67 by EMT-6 sarcoma. II. Studies in vivo (BALB/c mice): concise communication.

The EMT-6 sarcoma-like tumor of BALB/c mice can be grown as a solid subcutaneous transplantable tumor in vivo or as a monolayer culture in vitro. We have studied the uptake of gallium-67 by this tumor growing subcutaneously on the backs of 6-week-old BALB/c mice. After i.v. administration of Ga-67 citrate, tumor uptakes were as high as any others reported for mouse tumors. Also, for unknown reasons, there was appreciable reduction in tumor uptake with increasing amounts of Ga-67 citrate, even in the microcurie range. Furthermore, when mouse serum is prelabeled with Ga-67 and then injected, the EMT-6 uptake is greater than with Ga-67 administered as citrate (p less than 0.02). We believe that the finding of avid Ga-67 uptake in vivo helps to establish this unique in vivo/in vitro tumor system as a valid experimental model for studies regarding the mechanism of Ga-67 accumulation by neoplastic tissue.

Animals↗
PubMed1978

Mechanisms of localization of gallium-67 in tumors.

The mechanism of tumor localization of gallium-67 (67Ga) is not known with certainty, although much information has been derived regarding the biodistribution and subcellular fate of 67Ga in a variety of tumors and other tissues from experimental animals. After intravenous administration, 67Ga is bound to transferrin in the blood, and distributed to liver, lacrimal glands, salivary glands, and soft tissue tumors. Within the cells of the liver and tumors, gallium is found in lysosomes, and rough endoplasmic reticulum. Within these organelles, 67Ga is bound to a variety of macromolecules, including transferrin, ferritin, and a 45,000 molecular weight glycoprotein. Recent studies of tumor cells growing in tissue culture suggest an important role for transferrin in 67Ga tumor uptake. This uptake is mediated by a transferrin specific cellular receptor.

Animals↗
PubMed1978

Imaging the bowel with technetium--an aid in gallium studies.

Three cases are present to demonstrate the usefulness of oral or rectal technetium-99m preparations in locating the stomach and bowel in relation to abnormal accumulation of gallium-67 within the abdomen. In this way, the concentration of gallium in an abscess or a tumor may be distinguished from its physiologic excretion into the bowel.

Abdomen↗
PubMed1978

Cardiac chamber imaging: a comparison of red blood cells labeled with Tc-99m in vitro and in vivo.

A detailed comparison was performed between the quality of cardiac images obtained using red blood cells labeled in vitro and in vivo. Both methods gave cardiac images of high quality. The in vitro method resulted in subjectively superior images, better intravascular retention of injected radioactivity, and a higher left-ventricle-to-background count ratio (p less than 0.05). The differences in image quality and left-ventricular blood-pool activity were not great, however, and the slight advantage of the in vitro method was offset by a somewhat more complicated preparative procedure. We believe that both agents are suitable for radionuclide imaging of the cardiac chambers.

Erythrocytes↗
PubMed1977

The radionuclide ejection fraction: a comparison of three radionuclide techniques with contrast angiography.

Left-ventricular ejection fraction (EF) can be measured by several radionuclide methods. The EFs determined by three such methods (first-transit time-activity, equilibrium blood-pool time-activity, and equilibrium blood-pool area-length) were compared in 30 patients with EFs measured by area-length analysis of x-ray contrast angiograms. Both time-activity methods (first-transit and blood-pool) yielded EFs that correlated well with x-ray contrast EFs (r=0.86 and 0.84, respectively). Area-length analysis of blood-pool images yielded EFs that agreed less well with x-ray contrast EFs (r=0.73 in the RAO view, 0.70 in the LAO view). We conclude that first-transit and blood-pool techniques are equally accurate methods for determining EF when the time-activity method of analysis is employed.

Adult↗
PubMed1977

Gallium-67 citrate imaging in Hodgkin's disease: final report of cooperative group.

A large cooperative study of Ga-67 uptake in Hodgkin's disease showed that 88% of untreated patients had a positive uptake in one or more lesions. The percent of individual lesions seen on scan, however, was significantly lower; this indicated that negative findings at any one site do not argue strongly against the possiblilty of a lesion there. After treatment, the number of visualized lesions decreased sharply, but the exact role of Ga-67 in evaluating therapy is still not clear. Of the various histologic types of Hodgkin's disease, there was a high incidence of localization in all except the lymphocyte-predominance type, which showed a slightly lower uptake. No lesions less than 1 cm in diameter were successfully imaged and the size most easily detected was 4 cm in diameter. As expected, the imaging technique was much less successful for abdominal lesions than for those at other sites because of interfering concentration in bowel and liver. Both radiotherpy and chemotherapy tend to reverse the abnormalities seen on scan. The finding of a significant number of unsuspected positive lesions in asymptomatic patients returning for routine followup suggests that this is a distinctly valuable use of Ga-67, allowing early therpy for recurrences.

Gallium Radioisotopes↗
PubMed1977

The incorporation of Ga-67 into the ferritin fraction of rabbit hepatocytes in vivo.

Twenty-four hours after the administration of Ga-67 citrate and Fe-59 citrate, rabbits were killed and their livers removed and homogenized. Labile proteins in the filtered liver homogenates were denatured; ferritin was then crystallized from the supernatants by cadmium sulfate. Sephadex G-200 gel filtration of the ferritin fractions was done to determine the distribution of molecular weights in the substances associated with Ga-67 and Fe-59. It was found that Ga-67 was incorporated into the crystallizable ferritin fraction of rabbit hepatocytes with approximately one-sixth the uptake of simultaneously administered Fe-59. Gel-filtration chromatography confirmed that both the Ga-67 and the Fe-59 of the crystallizable ferritin fraction were associated with substances of the appropriate molecular weight for ferritin.

Animals↗
PubMed1976

Diagnosis of posterolateral congenital diaphragmatic (Bochdalek) hernia by liver scintigram: case report.

A characteristic liver scintigraphic finding was observed in a 2-month-old infant with hepatic herniation through a right-sided posterolateral congenital diaphragmatic defect (Bochdalek). The liver scintigrams showed an oblique band of decreased radioactivity dividing the liver into an inferior anteromedial portion and a superior posterolateral portion. In spite of the markedly abnormal liver scintigram, other diagnostic studies, including pneumoperitoneum abdominal radiography, remained negative. The liver scintigram can provide life-saving information in the diagnosis of congenital diaphragmatic hernia, as in the present case. The distinctive liver-scan findings among the various types of common diaphragmatic hernias are also briefly reviewed.

Colloids↗
PubMed1976

Possible enhancement of 67Ga-citrate imaging by iron dextran.

The whole-body retention of 67Ga-citrate was studied in intact and in abscess-bearing rabbits. The abscess-to-muscle ratio was obtained using a data processor. Administration of iron dextran lowers the whole-body retention in both the intact and abscess-bearing animals. The optimum time for administering the iron dextran was 24 hr after the 67Ga-citrate injection. At this time, the abscess-to-muscle ratio was highest and the cathode-ray screen images showed lowered back-ground activity and much better definition of the lesion.

Abscess↗
PubMed1976

Gallium-67 uptake by a malignant fibrous histiocytoma: case report.

Avid 67Ga-citrate uptake was observed in a malignant fibrous histiocytoma of the mediastinum. The realtionships of the tumor to the heart and liver was shown by 99mTc-sulfur colloid liver-spleen scanning and 99mTc-pertechnetate angiography performed in conjunction with a 67Ga-citrate whole-body scan. This is the first report of 67Ga-citrate uptake by this unusual tumor.

Adult↗
PubMed1976

Toadfish serum as a binder for in vitro assay of vitamin B12.

Serum from the oyster toadfish, Opsanus tau, has a binding capacity for cyanocobalamin 1,000 times greater than that of human serum. The binding follows the principle of isotope dilution in the physiologic range of vitamin B12 present in human serum. Under proper conditions of storage, this binder is stable for at least 1 year. Standard reagents and techniques used in other vitamin B12 competitive binding assays can be used with the toadfish serum binder. Toadfish serum offers potential advantages over intrinsic factor and human serum, the most commonly used binders in vitamin B12 assays.

Animals↗