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Biomedical subjects

T Machado

Publications and source records attributed to T Machado.

7 recordsLinked to original sources
PubMed1991

Variables affecting disc size in the lumbar spine of rabbits: anesthesia, paralysis, and disc injury.

Methods have been developed that permit repetitive radiographic measurement of the lumbar intervertebral disc space in a rostral-caudal direction (width) in the anesthetized laboratory rabbit. Using isolated control discs and injured discs in which narrowing has been induced for chronic and acute periods, the widths of the lumbar intervertebral disc spaces determined ratio-graphically correlate with widths determined histologically (p less than 0.000, r = 0.75). Both an increase (widening) and a decrease (narrowing) in disc width were observed using radiography after different experimental treatments. Anesthesia and lower-body paralysis (an experimentally induced inability to bear weight on and to perceive a pinch stimulus in hind limbs) caused widening of the discs: anesthesia causing a general widening throughout the lumbar spine and lower-body paralysis causing a specific widening low in the lumbar spine. Both disc injection and piercing the disc with needles to recover nucleus pulposus material caused narrowing of the discs. Acridine-orange injection induced a narrowing accompanied by osteophytosis. Experimentally induced narrowing at L4-5 (the result of injury to the disc) resulted in narrowing also at L2-3. These findings are consistent with the hypothesis that in vivo disc-width size in the young rabbit depends on both the quantity of nucleus pulposus material and the force-generating activities of the adjacent spinal muscles, and that disc injury at one level stimulates narrowing at other levels.

Acepromazine↗
PubMed1990

Growth related increase in rat intervertebral disc size: a quantitative radiographic and histologic comparison.

Methods were developed for measuring the width of lumbar intervertebral discs in Sprague-Dawley rats. Rates of growth of the L4-5 and L5-6 discs in a rostral-caudal direction in an approximately midsagittal plane were reported from analysis of radiographic and histologic data. The radiographic data correlated with histologic data (p less than 0.001). It was concluded that the L4-5 and L5-6 intervertebral discs continue to increase in size throughout the first 18 months of life of the rat, well past the age of rapid gain in body weight.

Animals↗
PubMed1990

The cavernosal acetylcholine/papaverine response. A practical in vivo method for quantification of endothelium-dependent relaxation. Rationale and experimental validation.

An in vivo method has been developed for quantifying cavernosal endothelium-dependent relaxation. The method is based on the fact that relaxation of the smooth muscle around the sinusoids of the penile corpora cavernosa activates the erectile veno-occlusive mechanism, and the degree of veno-occlusion can be precisely quantified by the pharmacologic maintenance erectile flow (PMEF) method. Pharmacologic maintenance erectile flows are determined after intracavernosal infusion of the endothelium-dependent relaxant acetylcholine (ACh) and the endothelium-independent relaxant papaverine, and expressed as an acetylcholine/papaverine ratio (APR). Control rabbits showed no changes from the test procedures themselves. In 12 test rabbits, control PMEFs after approximately 10(-7) mol ACh or papaverine averaged 0.7 and 0.5 ml/minute, respectively; APR averaged 1.3. Endothelial injury of the corpus cavernosum was produced by intracavernosal injection of 100 micrograms (16 x 10(-8) mol) of the detergent CHAPS or 1 ml of Renografin-76. Within 1 hour of injection of either agent, PMEF(ACh) increased markedly to approximately 6, PMEF(pap) increased minimally to approximately 0.9, and APR increased to about 7. These values gradually decreased to normal limits at six weeks. Endothelial injury and recovery were confirmed by electron microscopy. Thus, reduced cavernosal response to ACh relative to papaverine was indicative of endothelial injury. The ACh/papaverine response ratio offers promise as a practical and reliable in vivo method for quantifying endothelial-dependent relaxation.

Acetylcholine↗
PubMed1989

Pulsed-spray pharmacomechanical thrombolysis: preliminary clinical results.

Pulsed-spray pharmacomechanical thrombolysis was used to treat 41 patients with 47 complete thrombotic occlusions of hemodialysis grafts (n = 29), arterial bypass grafts (n = 10), or peripheral native arteries (n = 8). The procedure involves the use of small pulses of highly concentrated urokinase, which are forcefully sprayed throughout the thrombus during systemic heparinization. Virtually complete lysis was achieved in 46 of 47 occlusions. In the 46 thrombi that lysed, mean time for completion of lysis was 63 +/- 35 min and initial partial return of flow required 26 +/- 18 min. Complications included small peripheral emboli in one treated bypass graft (which cleared promptly after further pulse-spray therapy) and bleeding in three cases (one case of hematoma in the infused field at the site of recent surgery, one case of bilateral hematomas at the femoral puncture site, and one minor delayed self-limited gastrointestinal hemorrhage). Results to date suggest that the pulsed-spray pharmacomechanical method augments the speed, consistency, safety, and cost efficacy of clinical thrombolysis. Further study is warranted.

Arteriovenous Shunt, Surgical↗
PubMed1987

Production of penile veno-occlusive insufficiency by arterial occlusion in a canine model.

Angiographic evaluation of impotent men revealed a frequent association between penile arterial disease and veno-occlusive insufficiency of the corpora cavernosa. In order to evaluate a possible cause-and-effect relationship, we investigated the competence of the cavernosal veno-occlusive mechanism in a canine model at various intervals after onset of cavernosal ischemia. In most dogs, the veno-occlusive mechanism could no longer be activated by papaverine after about 30 minutes of ischemia. If ischemia was relieved shortly thereafter, veno-occlusive competence returned after a further delay of one or two hours. The evidence suggests that veno-occlusive failure is not simply a hemodynamic consequence of loss of arterial inflow, but instead secondary to some ischemic injury. We conclude that arterial insufficiency may be one of the causes of cavernosal veno-occlusive insufficiency in humans.

Animals↗