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Biomedical subjects

J B Fleming

Publications and source records attributed to J B Fleming.

32 records · Page 2Linked to original sources
PubMed1995

Miniaturized electrical stimulator with controllable duty cycles.

A stimulator with adjustable duty cycles is described for chronic electrical stimulation of skeletal muscles by way of a motor nerve. The stimulator is unique in that it can stimulate a muscle or group of muscles for 2-h intervals that alternate with variable periods of rest (2, 4, 6, 8, or 10 h). A given duty cycle is selected with a rotary switch at the beginning of an experiment and will continue automatically, without human intervention, for the duration of the experiment. Other features include an adjustable voltage output, a stimulation indicator light-emitting diode (LED), and a low-battery indicator LED. The stimulator is powered by two 9-V batteries or can be used with a bench-top power supply. The stimulation frequency (10 Hz) and pulse width (300 microseconds) are fixed in our design but can be changed to other values by substituting two of the resistors and one capacitor in accordance with simple formulas. We have used the stimulator in rat and rabbit experiments to stimulate the anterior tibialis and extensor digitorum longus muscles for up to 60 days. The timing and output of the stimulator were found to be stable and accurate over the entire 60-day period. The stimulator and batteries were carried in a jacket worn by the rabbits. In the rat experiments, the stimulator was used in a remote fashion with the electrical leads connected to the animals by way of a tethering system. In both animals, the electrodes were implanted adjacent to the common peroneal nerve.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗
PubMed1995

Laser therapy and angle-closure glaucoma.

All forms of primary and secondary pupillary block angle-closure glaucoma result in an increased resistance to aqueous flow at the pupil margin. As the pressure in the posterior chamber increases, the iris bows forward until the trabecular meshwork is occluded and aqueous outflow is interrupted. Most pupillary block glaucomas are ocular urgencies and require immediate medical therapy to lower intraocular pressure. The definitive treatment for pupillary block is laser therapy. By creating a hole in the iris, the pressure in the anterior and posterior chambers is equalized, allowing the angle to remain open. This discussion reviews the indications, contraindications, and techniques involved in the laser management of angle-closure glaucomas.

Glaucoma, Angle-Closure↗
PubMedDate not supplied

The surgical treatment of medullary thyroid carcinoma.

Medullary thyroid carcinoma (MTC) is a unique disease in solid tumor oncology due to its ability to secrete calcitonin (iCT), a highly sensitive and specific serum marker of persistent or recurrent disease even at a microscopic level. The relatively long duration of survival experienced by most patients with MTC combined with the visible nature of surgical complications, when they occur, has caused most surgeons to take a conservative approach to the operative management and follow-up of patients with MTC. In contrast, the patient, family physician, and endocrinologist watch the iCT slowly rise, indicative of persistent and usually progressive invasive cancer. Amidst this clinical dilemma, we developed a standardized diagnostic and operative strategy to maximize local-regional tumor control and facilitate patient management.

Calcitonin↗
PubMedDate not supplied

Development of an in vivo tumor-mimic model for learning radiofrequency ablation.

Radiofrequency ablation requires accurate probe placement using ultrasound guidance. The purpose of this study was to develop an in vivo tumor-mimic model for learning open and laparoscopic radiofrequency ablation. Tumor-mimics were created in ex vivo porcine livers by injecting a mixture of 3% agarose, 3% cellulose, 7% glycerol, and 0.05% methylene blue, which formed 1 cm hyperechoic, discrete lesions on ultrasound. Open and laparoscopic (using a box-trainer) ablation techniques were practiced. In vivo experiments were then conducted in 10 pigs. Three tumor-mimics were created in each animal using a laparoscopic approach. Lesions were characterized sonographically, ablated using an open (n = 5) or laparoscopic (n = 5) approach, and examined pathologically. An ablation in normal liver tissue was performed as a control. Tissue impedance was recorded. Target creation took 81 minutes per animal and 96% of injections were successful. Tissue impedance (48.8 +/- 5.8 vs. 49.6 +/- 5.4) and ablation size (25.1 +/- 3.4 vs. 24.3 +/- 5.1) were not significantly different for controls (n = 8) and tumor-mimics (n = 26), respectively. One animal died of a pulmonary embolism following injection of agarose into a hepatic vein. The agarose-based tissue-mimic creates realistic sonographic targets for learning ultrasound-guided open and laparoscopic radiofrequency ablation in an in vivo model.

Animals↗
PubMedDate not supplied

Sentinel lymph node biopsy identifies occult nodal metastases in patients with Marjolin's ulcer.

Since Marjolin's description, the management of burn scar carcinoma has remained controversial. A multitude of options and recommendations exist for the management of both primary lesions and regional nodal metastasis. This work reviews six cases of Marjolin's ulcer staged using sentinel lymph node biopsy. All primary lesions were confirmed to be squamous cell carcinoma and occurred a median of 29.5 years after burn. No patient had clinically detectable lymphadenopathy. In all cases, preoperative lymphoscintigraphy successfully identified a single draining regional nodal basin. Subsequent intraoperative lymphatic mapping/sentinel lymph node (SLN) biopsy was successful in five of six cases (83%). A successful intraoperative lymphatic mapping/SLN biopsy was defined as the identification of blue (uptake of isosulfan blue dye) or "hot" (uptake of radiolabeled sulfur colloid as measured with a handheld gamma counter) node(s) and subsequent excision. Four of five SLN biopsies identified previously occult nodal metastasis. SLN biopsy represents a minimally invasive and accurate staging procedure for Marjolin's ulcer.

Burns↗