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Biomedical subjects

K G Nelson

Publications and source records attributed to K G Nelson.

108 records · Page 6Linked to original sources
PubMed1975

Determination of stability constants of stannous fluoride complexes by potentiostatic titration.

The stability constants for stannous fluoride complexes were determined by potentiostatic titration. The method involves incremental additions of fluoride wherein each addition is followed by titration with stannous such that there is no change in the electromotive force developed between the fluoride ion and the reference electrodes. The values obtained were beta1 equals 4 times 10-3, b2 equals 1.1 times 10-7, and b3 equals 1 times 10-9. The results of this work suggest that the potentiostatic method wound be useful for determining stability constants in complexation systems involving an ion for which a specific on electrode is available.

Drug Stability↗
PubMed1975

Convective diffusion model for a transport-controlled dissolution rate process.

A mathematical model based on convective diffusion was developed to describe the rate of dissolution form the surface of a compressed compact. Experimental studies were carried out to test the model. The basic experimental apparatus consisted of a modified rotating-filter-stationary basket dissolution test apparatus. Dissolution rates from rectangular and circular surfaces of an homologous series of p-aminobenzoate esters permitted testing the theory with respect to solubility, geometry, and agitation conditions. The correlation between experimental results and theory was reasonalby good considering that the test conditions were somewhat less than ideal.

Aminobenzoates↗
PubMed1975

Evaluation of a convective diffusion drug dissolution rate model.

A recently introduced drug dissolution rate model based on convective diffusion was evaluated by experimentally determining dissolution rates. Alkyl p-aminobenzoates were used as the test compounds in a dissolution cell which promoted laminar flow of the liquid past the dissolving surface. The parameters evaluated were diffusivity, solubility, rate of shear, dissolving surface shape, and orientation of the surface relative to flow. The agreement between theory and experiment was quite satisfactory with respect to the functional dependence of the rate on these parameters as well as the actual magnitude of the rates.

Aminobenzoates↗
PubMed1975

Coccidioides immitis. A rare cause of pulmonary mycetoma.

Coccidioides immitis occurring as a fungus ball within a chronic pulmonary cavity has previously been reported twice and must be rare. We report a mycetoma composed of both spherule and mycelial forms of Coccidioides immitis, proved by culture and histologic sections. Fungus ball due to Coccidioides immitis is a logical progression from mycelia seen in the cavity wall in the active pulmonary coccidioidal lung cavity.

Coccidioides↗
PubMedDate not supplied

MR hysterosalpingography in a rabbit model.

Our objective was to evaluate the efficacy of MR imaging as compared with conventional hysterosalpingography (HSG) for the detection of fallopian tube patency after uterine injection of contrast material. Rabbit uterine horns (n= 18) were catheterized transvaginally. Five fallopian tubes were ligated and 11 were left unaltered. T1-weighted gradient-echo MR images were obtained before, during, and after injection of 1.0-3.0 mL of a dilute gadolinium-containing contrast agent. Corresponding conventional studies were performed with an equivalent volume of iohexol. Images were evaluated by two blinded readers. Observers agreed in all cases on the presence (n = 11) or absence (n = 5) of peritoneal spill with conventional HSG. Interpretation of MR HSG concurred with conventional HSG in 14 of 16 cases for each observer (P > .05). Reasons for misdiagnosis included small amounts of spill (n = 2), artifact (n = 1), and subtle spill between bowel loops (n = 1). Sensitivity and specificity for MR HSG were 95.5% and 70%, respectively, for the diagnosis of tubal patency/occlusions. No statistical difference was found between MR HSG and conventional HSG for the diagnosis of fallopian tube patency/obstruction. Potential advantages of MR HSG include no ionizing radiation, potentially diminished local contrast toxicity, superior visualization of uterine fibroids and endometriosis, and visualization of ovaries. We conclude that this technique warrants further study, including the use of a primate model to better simulate human anatomy.

Animals↗
PubMedDate not supplied

Chronic Ureaplasma urealyticum and Mycoplasma hominis infections of central nervous system in preterm infants.

In a prospective study of meningitis in 100 predominantly preterm infants, Ureaplasma urealyticum was isolated from the cerebrospinal fluid (CSF) of 8 and Mycoplasma hominis from the CSF of 5 babies undergoing investigation of suspected sepsis or treatment of hydrocephalus. U urealyticum was isolated from 6 infants with severe intraventricular haemorrhage and from 3 with hydrocephalus. In 4 babies multiple isolations were made over several weeks. There were clinical features of congenital infection with major neurological impairment in 1 infant infected with M hominis. Diagnosis is difficult because these organisms cannot be seen on gram stain and cannot readily be cultivated on routine bacteriological media, and CSF pleocytosis may be absent. This study, which used appropriate mycoplasmal media, shows that U urealyticum and M hominis are the most common microorganisms isolated from the CSF of newborn infants in a high-risk population.

Anti-Bacterial Agents↗
PubMedDate not supplied

Effects of very low birth weights on fetal and neonatal mortality rates in Alabama.

The relationship of births weighing less than 1,000 grams (g) to fetal and neonatal mortality rates, including changes over time, was studied. In Alabama during the period 1974-84, the percentage of reported births that weighed less than 500 g doubled, and the percentage of reported births weighing 500 to 999 g increased by about 10 percent. By the end of the study, while only 0.13 percent of reported births weighed less than 500 g, 24 percent of all stillbirths and 14 percent of all neonatal deaths were in this birth weight group. Similarly, in 1984, while only 0.62 percent of all births weighed 500 to 999 g, 23 percent of stillbirths and 42 percent of neonatal deaths were in this birth weight group. The data suggest that Alabama neonatal and fetal mortality rates declined more than was apparent in vital statistics data because of changes in reporting practices for very low birth weight newborns during the study period. Changes in vital statistics reporting are suggested to improve data reliability.

Alabama↗
PubMedDate not supplied

Physician opinions of preterm infant outcome and their effect on antenatal corticosteroid use.

Our purpose was to compare physician opinions about the appropriate use of corticosteroids with physician perceptions of preterm infant outcome. A total of 409 obstetricians and family physicians who provide maternity care in Alabama were surveyed to determine whether (and how) their perceptions of preterm infant outcome influenced their decision to use antenatal corticosteroids. Results were compared with those of a similar survey of Alabama physicians conducted in 1979. A total of 85% of physicians in 1992 versus 61% in 1979 reported that situations existed in which they would prescribe antenatal corticosteroids (p < 0.001). In 1992 physicians who underestimated preterm infant survival began corticosteroid use at later gestational ages than those physicians who did not underestimate survival (p < 0.02). In addition, 54% of physicians who underestimated preterm infant survival reported giving corticosteroids between 23 and 28 weeks' gestational age versus 73% of physicians with more accurate perceptions (p < 0.03). We conclude that in 1992, compared within 1979, more Alabama physicians reported antenatal corticosteroid use. Use of this treatment was influenced by each physician's perceptions of the probable outcome of the preterm infant.

Alabama↗