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L Waite

Publications and source records attributed to L Waite.

5 recordsLinked to original sources
PubMed1997

Automatic determination of patellofemoral kinematic parameters through X-ray image processing.

Examination of plain Merchant-view X-rays of the patellofemoral joint is often used to diagnose patellofemoral joint malalignment and to qualify the pathology. As digital image processing becomes more widespread, an image processing algorithm is being developed for medical personnel to easily display, manipulate and analyze digitized plain Merchant-view X-ray films on personal computers. The method provides measurement of the kinematic parameters: sulcus angle (SA), patellofemoral congruence angle (PFC), lateral patellar angle (LPA), patellar rotation angle (PR), and lateral patellar displacement (LPD). Smooth edges of the patella and the femur are obtained by using image enhancement, edge detection and morphological thinning techniques based on the thresholds chosen manually for boundary detection. Six landmarks for determining the kinematic parameters are marked automatically on the edges of patella and femur. Parameter measurements for twelve X-ray films of six patients are calculated for analysis and comparison with hand calculated parameters. The goal is develop an algorithm that can evaluate the geometry of the patellofemoral joint, and is cost effective.

Femur↗
PubMed1996

Nongenomic effects of progesterone on human intestinal smooth muscle cells.

Previous experiments demonstrated that progesterone affects intestinal smooth muscle cells through genomic and nongenomic pathways. We hypothesized that the nongenomic effect was mediated by changes in membrane excitability. We studied the effects of progesterone and other steroid hormones on a human intestinal smooth muscle cell line, using the whole cell patch-clamp technique. Ionic currents were elicited through steps from -70 mV to various test potentials. Progesterone dose-dependently reduced calcium currents. The decrease in inward current was partly due to a shift in the steady-state inactivation to more hyperpolarized potentials. This effect did not involve gene transcription, since it was not blocked by the progesterone antagonist ZK-98-299. The progesterone analogue 5-beta-dihydroprogesterone also decreased calcium currents, whereas its stereoisomer, 5-alpha- dihydroprogesterone, did not affect the properties of voltage-sensitive ion channels. Similarly, estradiol and dexamethasone did not alter inward currents. We conclude that progestins exert their nongenomic effects on intestinal smooth muscle cells by decreasing calcium currents. The change in the calcium signal may contribute to the reduction in muscle contraction observed after progesterone.

Cells, Cultured↗
PubMed1996

Patellofemoral joint study via image processing.

Plain Merchant-view X-rays of patellofemoral joints are used to study the geometry and kinematics of the patellofemoral joint. A method for calculating the kinematic parameters: sulcus angle (SA), patellofemoral congruence angle (PFC), lateral patellar angle (LPA), patellar rotation angle (PR) and lateral patellar displacement (LPD) is presented. Using digitized X-ray images of patellofemoral joints, contours of the patella and the femur can be acquired by boundary detection and morphological thinning. A radiograph is converted to a line drawing and the data points required for calculation of the parameters are chosen automatically without human intervention. Parameter measurements were demonstrated for 5 X-rays of 3 patients. Comparisons between computer calculated and hand calculated parameters were made. This technique is inexpensive but will provide the necessary information, and is practical, especially during the evaluation of patients with patellofemoral abnormalities.

Femur↗
PubMed1991

Mechanical characteristics and active tension generation in rat intestinal arterioles.

The contributions of active and passive wall tension to regulation of arteriolar diameters were determined for large (1A), intermediate (2A), and small (3A) arterioles in the small intestine of the anesthetized rat. Active tension (Ta) contributed greater than 85% of total wall force at rest in 2A and 3A and 75-80% of total force in 1A. Ta was approximately 90% of peak active tension (Ta,peak) for large through small arterioles, even though absolute Ta varied by fourfold. A linear relationship between microvascular pressure and Ta was observed for decreases in pressure in all arterioles. Ta remained nearly constant for pressure increases of 40% in 2A and 3A but was increased in 1A. Because of the plateau of the circumference-Ta relationship near Ta,peak, superfusion of progressively increasing concentrations of norepinephrine or adenosine resulted in maintenance of the close Ta-Ta,peak relationship unless the vessel diameter changed greater than 25%. These results indicate that, while arteriolar diameters vary substantially, near-peak Ta is generated for a variety of physiological conditions.

Adenosine↗