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Biomedical subjects

J T Thompson

Publications and source records attributed to J T Thompson.

At least 19 recordsLinked to original sources
PubMed1992

The absorption of mixtures of air and perfluoropropane after pars plana vitrectomy.

The duration of mixtures of perfluoropropane and air (0% to 20% C3F8) were analyzed in 206 eyes following pars plana vitrectomy for a variety of vitreoretinal disorders using a noninvasive model for calculating the intraocular gas bubble volume. The accuracy of the noninvasive model was tested by comparing the estimated bubble volume with the actual volume withdrawn from 12 eyes with intraocular gas bubbles undergoing a subsequent vitrectomy. The method for estimating intraocular bubble volume had a mean difference between the actual and estimated bubble volume of 0.1 +/- 0.35 mL. The half-life of air (0% C3F8) was 1.3 +/- 0.1 days; 5% C3F8, 4.2 +/- 0.1 days; 10% C3F8, 6.5 +/- 0.2 days; 15% C3F8, 8.0 +/- 0.6 days; and 20% C3F8, 12.5 +/- 1.1 days. The difference between each half-life was statistically significant (P < .01). Linear regression analysis of the half-lives of C3F8 mixtures of up to 20% C3F8 showed a linear increase in half-lives with increasing concentrations of C3F8. The duration of intraocular gas tamponade can be controlled by selecting the appropriate concentration of air and C3F8.

Absorption↗
PubMed1992

Isolated lung transplantation for end-stage lung disease: a viable therapy.

Since January 1990, we have performed 29 isolated lung transplantations in 28 patients with end-stage lung disease (12 single, 16 bilateral). Recipient diagnoses were: cystic fibrosis (11), chronic obstructive pulmonary disease (6), pulmonary fibrosis (6), eosinophilic granulomatosis (1), postinfectious lung disease (1), adult respiratory distress syndrome (1), and primary pulmonary hypertension (2). There have been four deaths, two in patients with pulmonary fibrosis and two in patients with primary pulmonary hypertension. Four patients have undergone transplantation while on ventilatory support for respiratory failure (2 with cystic fibrosis, 1 having redo lung transplantation with cystic fibrosis, and 1 with adult respiratory distress syndrome); all of these have survived. Six patients required cardiopulmonary bypass, which was associated with increased transfusion requirement. All patients 2 months after discharge have returned to an active life-style, except for 2 patients who currently await retransplantation. Preoperative pulmonary rehabilitation has resulted in significant improvement in exercise performance in all patients. Immunosuppression consists of cyclosporine, azathioprine, and antilymphoblast globulin (University of Minnesota), withholding systemic steroids in the early postoperative period. We have employed bronchial omentopexy in all but four transplants; there has been one partial bronchial dehiscence, two instances of bronchomalacia requiring internal stenting, and one airway stenosis. Cytomegalovirus disease has been seen frequently (15 cases), but has responded well to treatment with ganciclovir. Other complication shave included one drug-related prolonged postoperative ventilation, thrombosis of a left lung after bilateral lung transplantation requiring retransplantation, five episodes of unilateral phrenic nerve palsy after bilateral lung transplantation (4 resolved), and the requirement of massive transfusion (greater than 10 units) in 5 patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Lasers in dermatology and ophthalmology.

Dermatology and ophthalmology are two specialties that have made exceptional use of laser technology. In dermatology, port wine stains and hemangiomas, neoplastic lesions, and adnexal tumors are amenable to laser treatment. In ophthalmology, the use of lasers to effect photocoagulation, photoradiation, photovaporization, photodisruption, and photodecomposition has permitted the treatment of vascular retinal disease, macular edema, intraocular tumors, open angle glaucoma, and angle closure glaucoma. Although great strides in laser technology have been made, the future is even more promising as laser devices are further modified to treat specific disease processes.

Eye Diseases↗
PubMed1992

Retinal cartography. An analysis of two-dimensional and three-dimensional mapping of the retina.

The current two-dimensional (2D) retinal drawing chart is an azimuth equidistant representation of the retina. The distortion produced by this chart was analyzed and compared to other 2D projections, such as stereographic, equal area, and orthographic maps of the retina. Circumferential distortion was calculated for lesions at varying distances from the macula using the azimuth equidistant retinal map and was found to increase exponentially as a function of the distance from the macula. Circumferential distortion was 57.1% at the equator, 88.5% 3 mm anterior to the equator, and 137.8% 6 mm anterior to the equator. A three-dimensional (3D) model of the retinal surface was created using 3D computer assisted design (CAD) software. This 3D model was able to represent retinal lesions such that their true size, shape, location, and orientation were all conserved. Retinal lesions could be viewed from multiple angles and examined in cross section. The use of 3D CAD software coupled with ultrasound or magnetic resonance imaging data has the potential to represent retinal lesions more accurately than current methods.

Choroid Neoplasms↗
PubMed1991

Microinjection of the dopamine antagonist cis-flupenthixol into the MPOA impairs copulation, penile reflexes and sexual motivation in male rats.

Microinjection of the dopamine antagonist cis-flupenthixol into the medial preoptic area was previously shown to impair male rat copulatory behavior. The present experiments provide further evidence of cis-flupenthixol's inhibitory effects on male sexual behavior. Following microinjections of moderate to high doses of cis-flupenthixol, males exhibited slower copulatory rates and fewer ejaculations in copula, fewer ex copula erections and penile movements, and reduced sexual motivation in an X-maze. Locomotion in the X-maze was not significantly affected. Microinjections of the inactive isomer trans-flupenthixol produced no change in any behavioral measure, indicating that cis-flupenthixol's effects were receptor mediated. We suggest that dopamine receptors in the MPOA influence copulation primarily by regulating reflexive and motivational factors, but not locomotion.

Animals↗
PubMed1991

Dose dependent D2 effects on genital reflexes after MPOA injections of quinelorane and apomorphine.

This study investigated the effects on genital reflexes of unilateral MPOA injections of 0.1, 1, 3, and 10 micrograms of the D2 agonist quinelorane (LY-163502), and of 3 micrograms quinelorane administered together with 3 micrograms of the D1 antagonist SCH-23390. In addition, the effects of an MPOA injection of 10 micrograms apomorphine were tested. All but the lowest dose of quinelorane significantly decreased the latency to the first reflex. The 3 and 10 micrograms doses of quinelorane, and the combination of quinelorane and SCH-23390, decreased the total number of reflexes. In addition, 10 micrograms quinelorane increased the number of seminal emissions. 10 micrograms apomorphine, like 10 micrograms quinelorane, decreased the latency to the first reflex and increased the number of seminal emissions, but did not decrease the numbers of erections or penile movements. The ratio of D1/D2 activity may influence the number of erections displayed during ex copula testing.

Animals↗
PubMed1991

D2 receptors in the paraventricular nucleus regulate genital responses and copulation in male rats.

The D2 dopamine receptor agonist quinelorane (LY-163502), microinjected into the paraventricular nucleus (PVN), affected genital response of restrained supine male rats in a biphasic dose-dependent fashion. A moderate dose (1 microgram) facilitated penile responses (intense erections and penile movements), and decreased the latency to the first response. A high dose of quinelorane (10 micrograms) facilitated seminal emission while inhibiting penile responses. The addition of the D1 antagonist SCH-23390 to the 1 microgram dose of quinelorane potentiated quinelorane's increase in seminal emission. We suggest that D1 receptors in the PVN may be antagonistic to D2 receptor-mediated seminal emission, and possibly also penile responses. In copulation tests 1 microgram quinelorane decreased mount latency, whereas 10 micrograms quinelorane increased mount and intromission latencies and slowed copulatory rate. Both 1 and 10 micrograms quinelorane, and also 1 and 10 micrograms of the mixed D1 and D2 agonist apomorphine, decreased the number of intromissions preceding ejaculation.

Animals↗
PubMed1990

Dopamine receptors in the ventral tegmental area modulate male sexual behavior in rats.

The mesocorticolimbic dopamine tract is considered to be a substrate for motivation and reward as well as for locomotor behavior. The present experiments assessed the role of dopamine cell bodies in the ventral tegmental area (VTA), the source of this tract, in the copulatory behavior of male rats. The dopamine agonist apomorphine or the dopamine antagonist cis-flupenthixol were microinjected into the VTA immediately before sexual behavior tests with a receptive female. Apomorphine delayed the onset of copulation and slowed its rate, presumably by stimulating somatodendritic autoreceptors and thereby decreasing the firing rate of VTA neurons. Control injections of apomorphine into the substantia nigra were without effect. cis-Flupenthixol, which would have blocked autoreceptors and thereby depolarized VTA neurons, shortened the latency to begin copulating in those animals that did copulate; however, fewer animals exhibited sexual behavior. One possible explanation for the apparently contradictory effects of cis-flupenthixol may be that VTA neurons increased their rate of firing in some animals, leading to a faster onset of copulation, but that in other animals depolarization block in a substantial number of neurons resulted in a lack of copulation. These results are consistent with a contribution of the mesocorticolimbic dopamine tract to motivational and/or motor aspects of male copulatory behavior.

Action Potentials↗
PubMed1990

Flow dynamics of extrusion needle vacuuming in a closed vitrectomy system.

The dynamics of pressure, flow, and ocular volume relationships were examined with respect to extrusion needle use in simulated vitrectomy. Glass-stoppered bottles used with infusion lines with drip chambers lowered the intraocular pressure 4 to 7 inches below the fluid level in the bottle, varying with the amount of fluid in the bottle. Compared with flow rates using the regular tip needle with the steel infusion cannula, the disposable infusion cannula lowered the flow rate by about 25% and the tapered tip extrusion needle decreased outflow by 40% to 50%. Tracer dilution rates were decreased by the use of the disposable infusion port or the aphakic model eye; however, 2 minutes of infusion at a 30-inch bottle height dilution was still sufficient to wash out the tracer to less than 5% of the original concentration.

Humans↗
PubMed1990

Assessment of visual-field changes before and after focal photocoagulation for clinically significant diabetic macular edema.

Visual fields were compared before and after focal photocoagulation for eyes with nonproliferative diabetic retinopathy and clinically significant diabetic macular edema. A total of 8 eyes was tested before treatment and 6-8 weeks after treatment using static automated visual fields (Octopus). The visual-field indices, mean defect (MD) and corrected loss variance, were employed as measures of retinal sensitivity. Our results show that focal photocoagulation (CLV) generally depressed sensitivity (increased MD) in the treated central 10 degrees field, whereas in the untreated control region (10-30 degrees) sensitivity generally remained stable. However, the whole-field indices indicated that overall the fields remained stable following focal photocoagulation treatment. These results suggest that although focal treatment produces local absolute visual-field defects, the effects are small relative to the global indices.

Adult↗
PubMed1990

Assessment of the dynamics of allograft rejection utilizing Tc-99m labeled lymphocytes.

The feasibility of utilizing technetium 99m (Tc-99m) lymphocytes labeled by a modified stannous chloride technique for the assessment of cardiac allograft rejection was examined. Syngeneic lymphocytes were labeled with Tc-99m at 125 microCi per 10(7) cells. Mean labeling efficiency was 67 +/- 17%, n = 44. Two groups of rats allogeneic (ALLO) (ACI/Lewis) and syngeneic (SYN) (Lewis/Lewis) were injected with labeled cells at two, four, five, and seven days post cardiac graft. At 20 hr post-injection, transplant and native hearts were harvested for radioanalysis and histology. Ratio of percent dose per gram transplant heart to native heart (T/N) revealed a significant difference between ALLO (T/N = 2.7 +/- 0.23, n = 5) and SYN (T/N = 1.73 +/- 0.12, n = 5) at two days P[F] = 0.0045. Maximum difference occurred at five days with ALLO mean T/N of 6.40 +/- 0.54, n = 5 (P[F] = 0.0001). There was no significant difference at seven days post graft with ALLO 2.85 +/- 0.30, n = 5 and SYN 2.02 +/- 0.05, n = 5 (P[F] = 0.0166). SYN rat T/Ns did not change significantly (mean 1.83 +/- 0.10, n = 18) at the various time periods.

Animals↗
PubMed1990

RPE-mediated collagen gel contraction. Inhibition by colchicine and stimulation by TGF-beta.

Retinal detachment secondary to proliferative vitreoretinopathy (PVR) is often precipitated by traction on the retina from preretinal membranes and traction on the vitreous base. Contraction and proliferation of retinal pigment epithelial (RPE) cells appear to play an important role in the pathogenesis of PVR. Contraction of collagen gels by human RPE cells was evaluated as a model of tractional forces on the vitreous gel. The area of collagen gels with admixed RPE cells in 15-mm wells was measured daily. The collagen gels contracted to less than 50% of original area in 89% of wells. Colchicine (0.01-1 microM) inhibited RPE-induced collagen gel contraction, whereas 1 ng/ml of transforming growth factor-beta enhanced it. Potential stimulators or inhibitors of RPE-mediated gel contraction can be tested using this model.

Aged↗
PubMed1989

The effects of intracranial administration of the dopamine agonist apomorphine on penile reflexes and seminal emission in the rat.

Previous studies employing systemic administration of the dopamine agonist apomorphine have shown that the dose response curves for apomorphine's effects on penile reflexes and seminal emission differ, suggesting that experimentally separable populations of dopamine receptors regulate these two responses. The present experiments examined the locations of central nervous system DA receptors mediating genital responses in the restrained, supine rate by injecting apomorphine into the medial preoptic area and the paraventricular nucleus through chronic, indwelling cannulae. Medial preoptic area injections facilitated penile reflexes, but not seminal emission, while paraventricular injections facilitated seminal emission. These results suggest that systemically administered apomorphine may facilitate penile reflexes by acting on the medial preoptic area and may enhance seminal emission by acting on the paraventricular nucleus.

Animals↗
PubMed1989

Kinetics of intraocular gases. Disappearance of air, sulfur hexafluoride, and perfluoropropane after pars plana vitrectomy.

Intraocular gas bubbles are an important source of internal tamponade for the treatment of retinal breaks in eyes requiring vitrectomy. The kinetics of disappearance of air, 20% sulfur hexafluoride, and 10% perfluoropropane were prospectively evaluated in 76 eyes undergoing pars plana vitrectomy. The absorption of each gas approximated a first-order kinetic equation with respect to bubble volume. The half-life of air was 1.6 days in phakic and 0.9 days in aphakic eyes. The half-life of 20% sulfur hexafluoride was 2.8 days in phakic and 2.4 days in aphakic eyes. The half-life of 10% perfluoropropane was 5.7 days in phakic, 4.5 days in aphakic, and 4.3 days in pseudophakic eyes. The difference in half-life among the three gases was significant. Intraocular gases had a shorter half-life in aphakic than in phakic eyes.

Absorption↗
PubMed1989

The effects of intrathecal administration of the dopamine agonist apomorphine on penile reflexes and copulation in the male rat.

Relatively high doses of systemically administered apomorphine inhibit penile reflexes. It is possible that these inhibitory effects are due, at least in part, to actions of apomorphine on the lumbosacral spinal cord. The present experiments examined this possibility by injecting apomorphine (10 and 50 micrograms/5.0 microliters vehicle) into the lumbosacral subarachnoid space through chronic, indwelling cannulae. Such injections impaired ex copula penile reflexes, slowed the rate of copulation, and decreased the number of intromissions preceding ejaculation. These results suggest that lumbosacral cord dopamine receptors may normally regulate male sexual performance.

Animals↗
PubMed1989

Quinelorane (LY163502), a D2 dopamine receptor agonist, facilitates seminal emission, but inhibits penile erection in the rat.

Dopaminergic compounds have been shown to facilitate male sexual responses in various contexts. We investigated the effects of a specific D2 dopamine receptor agonist, quinelorane (LY163502), on sexual responses elicited in the restrained supine male rat (i.e., ex copula reflex tests). Penile erections, evoked by retraction of the penile sheath, were inhibited by systemic administration of 10 micrograms/kg quinelorane; however, the occurrence of seminal emission was dramatically increased. A smaller dose of 0.25 ng/kg was without effect. In a second experiment, intracranial microinjection of quinelorane was followed by ex copula reflex tests. The medial preoptic area (MPOA) has been previously implicated in the dopaminergic regulation of male copulatory behavior. The effects of an intra-MPOA injection of quinelorane on seminal emission and erectile responses were similar to those observed following systemic administration. These results are consistent with the hypothesis that DA receptors in the MPOA are important in the regulation of male sexual behavior and suggest that D2 receptors in the MPOA may decrease ejaculatory threshold while inhibiting erectile mechanisms.

Animals↗
PubMed1989

D2/D1 ratio in the medial preoptic area affects copulation of male rats.

The D1/D2 dopamine agonist apomorphine, microinjected into the medial preoptic area (MPOA), facilitates male rat sexual behavior and the D1/D2 antagonist cis-flupenthixol in the MPOA impairs it. The present study investigated the roles of D1 and D2 receptors in the regulation of copulation by microinjecting drugs selective for these receptors into the MPOA. The D2 agonist LY-163502 delayed the onset and slowed the rate of copulation and also reduced the number of vaginal intromissions required to trigger ejaculation (reduced ejaculatory threshold). The D1 agonist SKF-82526 had no effect, either alone or together with LY-163502. The D1 antagonist SCH-23390 delayed the onset of copulation and decreased ejaculatory threshold, as had the D2 agonist. A low dose of the D2 agonist alone and together with the D1 antagonist delayed the onset of copulation and reduced ejaculatory threshold; the combination of drugs was more effective than LY-163502 alone. Only the combination of drugs slowed the rate of copulation and delayed the resumption of copulation after an ejaculation. Thus, increasing the D2/D1 ratio in the MPOA, by selective stimulation of D2 and/or antagonism of D1 receptors, delays the onset of copulation and reduces ejaculatory threshold, possibly by altering autonomic control of penile reflexes.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗