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Biomedical subjects

M L Johnson

Publications and source records attributed to M L Johnson.

At least 307 records · Page 17Linked to original sources
PubMed1981

Analysis of data from the analytical ultracentrifuge by nonlinear least-squares techniques.

Least-squares analysis of experimental data from the analytical ultracentrifuge is discussed in detail, with particular attention to the use of interference optics in studying nonideal self-associating macromolecular systems. Several samples are given that describe the application of the technique, the expected precision of the results, and some of its limitations. A FORTRAN IV computer program is available from the authors.

Computers↗
PubMed1981

Complementary role of Tc-99m-diethyl-IDA and ultrasound in large and small duct biliary tract obstruction.

Fifty-one patients underwent both radionuclide and ultrasound studies of the hepatobiliary system. Eleven patients had large bile duct obstruction, six had intrahepatic diffuse small duct obstruction, and 37 had no obstruction. In all 11 patients with large duct obstruction, the radionuclide images were abnormal, but in nine of these studies the level of obstruction could not be determined. Ultrasound was abnormal in nine studies (with correct identification of level), normal in one, and technically inadequate in one, ultrasound scans were also abnormal in six patients without obstruction. In small duct obstruction, the radionuclide scan was abnormal in all six, but in five patients it could not differentiate small from large duct obstruction. In all six patients, ultrasound showed no large duct obstruction, thus allowing identification of the level of obstruction in patients whose radionuclide scans were equivocal. A cost analysis indicated that in suspected large duct obstruction, the best strategy is ultrasound first, followed by radionuclide imaging in all positive or technically inadequate ultrasound studies. In suspected small duct obstruction, the best strategy is radionuclide scanning first followed by ultrasound in all Tc-99m-diethyl-IDA studies equivocal as to level of obstruction.

Cholestasis, Intrahepatic↗
PubMed1981

Hepatic focal nodular hyperplasia: angiography, CT, sonography, and scintigraphy.

Eleven patients with focal nodular hyperplasia of the liver underwent a combination of radiologic procedures, including sonography, computed tomography (CT), hepatic scintigraphy, and angiography. This paper describes the radiologic findings in this group of patients and reviews the current literature. In the present series, sonography was the most sensitive (100%) method for detection of focal nodular hyperplasia, while CT was able to detect only seven (78%) of nine cases. Arteriographic findings were felt to be characteristic in nine (82%) of 11 cases. Hepatic scintigraphy demonstrated normal colloid uptake in six (55%) of 11 lesions. In this series, an accurate radiologic diagnosis of focal nodular hyperplasia was made in 73% of cases. Hepatic scintigraphy is the pivotal examination. Normal colloid uptake by a focal hepatic mass is virtually diagnostic. However, in the patients in whom the colloid scan shows decreased or absent uptake, angiography may show findings diagnostic of focal nodular hyperplasia in up to 75% of cases, thus avoiding the need need for liver biopsy or surgery.

Adolescent↗
PubMed1981

Fetal transfusion with real-time ultrasound guidance.

A technique of fetal transfusion using sonographic guidance for needle placement is described. Sixteen patients underwent a total of 43 transfusions. The fetal mortality risk appears to be lower than that encountered in fluoroscopy-directed transfusions. Fetal irradiation has been dramatically reduced from an average of 2.2 rads per transfusion to 0.29 rads per transfusion. The technique allows very precise placement of a needle within the uterus or fetus. We have used it in difficult cases for amniocentesis. The technique could also be adapted to other problems requiring accurate placement of a needle within the body, such as biopsy of masses or aspiration of cysts.

Blood Transfusion, Intrauterine↗
PubMed1981

Neonatal intracranial hemorrhage and maternal use of aspirin.

A prospective study of 108 infants born at 34 weeks' gestation or earlier or weighing 1500 g or less was carried out to determine the incidence of intracranial hemorrhage and the multiple risk factors that may cause or aggravate this hemorrhage in premature infants. On day 2 post partum, mothers were questioned regarding maternal risk factors, including the use of either aspirin or acetaminophen during the last week of pregnancy. Between days 3 and 7 post partum, computed tomographic scanning was performed on the 108 infants. Of the total, 53 (49%) developed intracranial hemorrhage. The incidence of hemorrhage in the infants whose mothers had ingested aspirin was significantly greater (P less than .05) than that seen in infants whose mothers did not take either aspirin or acetaminophen (control group). The incidence of intracranial hemorrhage among infants whose mothers ingested acetaminophen was not significantly different from that of the control group. This study indicates that aspirin is associated with an increased incidence of intracranial hemorrhage in the authors' population. The use of aspirin in the last 3 months of pregnancy is highly questionable and probably inappropriate.

Acetaminophen↗
PubMed1980

Molecular properties of the reassembled coat protein of coated vesicles.

Clathrin has been prepared from human and bovine brains by a rapid technique which does not require sucrose gradient centrifugation. The promoter molecule which is obtained has the ability to polymerize and form protein coats, i.e., so-called cages or baskets, which resemble the structures observed in coated vesicles. The polymerization of clathrin to form cage structures in 0.2 M ammonium acetate, pH 6.8, results in two distributions of sedimenting particles in the ultracentrifuge, one centered near 300S and the other near 150S. Equilibrium sedimentation gives molecular weights of the 150S and 300S particles near 25 million and 100 million, respectively. The turbidities of the two species have been measured during centrifugation in the ultracentrifuge. When the turbidity values are combined with the molecular weight values, the radii of the 150S and 300S species can be obtained, assuming a hollow sphere as a model for the clathrin polyhedral molecules.

Animals↗
PubMed1980

Effects of pregnancy and contraceptive steroids on gallbladder function.

We used real-time ultrasonography to study gallbladder kinetics in 11 nonpregnant women, 17 women using steroid contraceptives, and 33 pregnant women. Gallbladder volume was determined after an overnight fast and serially for 90 minutes after a standard liquid meal. After the first trimester of pregnancy, gallbladder volume during fasting and residual volume after contraction were twice as large as in control subjects. The rate of emptying and the percentage emptied were reduced. In early pregnancy the only important abnormality was a 30 per cent decrease in emptying rate. Gallbladder function was not affected by contraceptive steroids. Incomplete empyting of the gallbladder in late pregnancy leaves a large residual volume and may cause retention of cholesterol crystals, a prerequisite for cholesterol-gallstone formation. These findings are consistent with the view that pregnancy increases the risk of cholesterol gallstones. The increased incidence of gallstones associated with contraceptive steroids does not involve abnormal gallbladder kinetics.

Bile↗
PubMed1980

Evaluation of fetal intracranial anatomy by static and real-time ultrasound.

Improvements in ultrasound technology have now made possible detailed visualization of fetal intracranial anatomy. Structures such as the midbrain, thalami, and lateral ventricles can be routinely imaged. Measurements of the ratio between lateral ventricular width and cerebral hemispheric width demonstrate a steady decrease from a mean of 56% at 15 wk gestation to 28% at term reflecting the relatively more rapid growth of the cerebral hemispheres as compared with the cerebral ventricles. Application of this new ultrasound data greatly facilitates accurate and consistent biparietal diameter estimations and early diagnosis of fetal hydrocephalus and other fetal cranial anomalies. This article describes the axial fetal cranial anatomy as demonstrated sonically and includes a table for normal fetal ventricular size at various gestational ages, based on evaluation of 196 normal fetuses. Some of the more common fetal cranial anomalies amenable to ultrasound diagnosis in utero are discussed.

Brain↗
PubMed1980

In defense of data.

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Health Services Research↗