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Biomedical subjects

T B Jones

Publications and source records attributed to T B Jones.

At least 19 recordsLinked to original sources
PubMed1990

Dielectrophoretic spectra of single cells determined by feedback-controlled levitation.

In this paper we have utilized the principle of dielectrophoresis (DEP) to develop an apparatus to stably levitate single biological cells using a digital feedback control scheme. Using this apparatus, the positive DEP spectra of both Canola plant protoplast and ligament fibroblast cells have been measured over a wide range of frequencies (1 kHz to 50 MHz) and suspending medium conductivities (11-800 muS/cm). The experimental data thus obtained have been interpreted in terms of a simple spherical cell model. Furthermore, utilizing such a model, we have shown that various cellular parameters of interest can be readily obtained from the measured DEP levitation spectrum. Specifically, the effective membrane capacitance of single cells has been determined. Values of 0.47 +/- 0.03 muF/cm2 for Canola protoplasts and 1.52 +/- 0.26 muF/cm2 for ligament fibroblasts thus obtained are consistent with those determined by other existing electrical methods.

Cell Membrane↗
PubMed1990

Preconceptional planning.

Preconceptional counseling has become an important part of obstetrical care. The concept of preconceptional planning is discussed in detail, with an emphasis on particular high-risk groups. The role of genetics and fetal diagnosis is also examined.

Adult↗
PubMed1986

Femur length/abdominal circumference ratio. Poor predictor of macrosomic fetuses in diabetic mothers.

Antenatal diagnosis of fetal macrosomia can affect the management of diabetic mothers. Because the sonographically determined femur length/abdominal circumference (FL/AC) ratio has been shown to differ in macrosomic and non-macrosomic fetuses (in a population containing few diabetics), its value in establishing the diagnosis of macrosomia was examined. The results indicate that the FL/AC ratio differs in non-macrosomic (20.4 +/- 1.6) and macrosomic (19.5 +/- 1.4) fetuses of diabetic mothers, but there is considerable overlap. For no cutoff value is there a high sensitivity and high specificity. The positive predictive value is 36-43 per cent (depending on the cutoff), only slightly greater than the prevalence (26 per cent in the study population). The authors conclude that the FL/AC ratio is not useful in predicting macrosomia among diabetic mothers.

Abdomen↗
PubMed1986

Ultrasound guidance for selected dilatation and evacuation procedures.

Intraoperative ultrasound was used as an adjunct in difficult dilatation and evacuation (D&E) procedures for first-trimester abortions. This technique was useful in eight technically difficult D&Es in the presence of acute retroflexion, acute anteflexion, cervical stenosis and lower uterine segment fibroids.

Abortion, Therapeutic↗
PubMed1985

FL/AC ratio: poor predictor of intrauterine growth retardation.

Early antenatal detection of intrauterine growth retardation (IUGR) may decrease the associated perinatal morbidity and mortality. A parameter based on sonographically measured femur length (FL) and abdominal circumference (AC), expressed as FL/AC X 100 and termed the FL/AC ratio, has recently been proposed by Hadlock et al as an age-independent predictor of IUGR. We studied 285 normal and 37 IUGR fetuses to verify that the FL/AC ratio is independent of gestational age (GA) and to assess its value as a predictor of IUGR. Our results confirm that the FL/AC ratio is age-independent above 20 weeks and that its mean value differs in normal (22.4 +/- 1.7) and IUGR (23.7 +/- 1.4) fetuses (P less than .01, t-test). Because of considerable overlap between these two groups, however, there is no cutoff value for the FL/AC ratio that yields both a high sensitivity and a high specificity, or that leads to a high positive predictive value. With a cutoff of 23.5, for example, the sensitivity is 56% and the specificity 74%, and, even assuming an IUGR prevalence rate of 10%, the likelihood of IUGR in a fetus with an FL/AC ratio above the cutoff is only 19%. We conclude that the FL/AC ratio, though an age-independent measure whose mean value differs in normal and IUGR fetuses, is not clinically useful as a predictor of IUGR.

Abdomen↗
PubMed1985

Prediction of fetal lung maturity: inaccuracy of study using conventional ultrasound instruments.

The ability of three ultrasound (US) parameters--echogenicity, texture, and through transmission--to predict fetal lung maturity was tested in 59 patients using currently available clinical US equipment. The chi square test was used to determine whether there was an association between any single parameter and a "mature" lecithin/sphingomyelin (LS) ratio or specific phosphatidycholine (SPC). Multiple linear regression analysis was used to assess the combined ability of these three parameters and gestational age to predict LS ratio and SPC. There was no correlation between fetal lung maturity, as determined by mature LS and SPC indices, and the US parameters tested using unmodified clinical equipment.

Amniocentesis↗
PubMed1983

Sonographic determination of renal volumes in normal neonates.

Renal diseases that affect renal size without altering renal architecture require a quantitative means of detection. A prospective study was undertaken to establish normal values for renal volumes in healthy neonates using sonography. Volumes were determined by two methods; (1) the serial area-volume method using parallel transverse images; and (2) the prolate ellipsoid model of the kidney using orthogonal diameters taken from ultrasound images. Renal volumes for both the right and left kidneys in both sexes were found to be approximately 10 ml. There was no significant difference between the results obtained by either method, nor were there significant differences between the volumes of the right and left kidneys within either sex. No difference in renal volume was noted between sexes. The mean greatest renal length was also computed for right and left kidneys in both sexes. Knowledge of normal renal volumes may aid in the diagnosis of urinary system disorders in neonates.

Female↗
PubMed1983

Ultrasonographic determination of renal mass and renal volume.

Volumes and surface areas of 45 kidneys were determined ultrasonographically in vivo before autopsy and in a water bath phantom after autopsy by means of both the ellipsoid and the stepped section methods. Comparison of results revealed that renal volume may be determined by the simplest method, the ellipsoid method, with sufficient accuracy for clinical use. Results also revealed that renal mass expressed in grams may be directly obtained from renal volume expressed in milliliters, but mass in grams was found to correlate better with renal surface area than with renal volume. A formula relating renal mass to both volume and surface area was developed from regression analysis of the data and was found to provide a more precise estimate of renal mass than does mass computed from either volume or surface area alone.

Humans↗
PubMed1983

Abrupt termination of the common bile duct: a sign of malignancy identified by high-resolution real-time sonography.

Although contrast cholangiography has a greater accuracy than sonography in determining the precise nature of extrahepatic biliary obstruction, it is not without risk. High-resolution real-time sonography is frequently adequate to evaluate the extrahepatic biliary system in multiple planes without known risk to the patient. In a one-year period the authors prospectively observed eight instances of distal biliary obstruction with abrupt termination of the common bile duct, and all were associated with malignant obstruction. There was no instance of abrupt ductal termination secondary to benign disease in this series. Malignancy should be suspected when careful sonograms along the longitudinal axis of an obstructed distal common bile duct reveal an abrupt termination.

Aged↗