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Biomedical subjects

G Field

Publications and source records attributed to G Field.

At least 19 recordsLinked to original sources

Acoustic satellite behaviour in the Australian bushcricket Elephantodeta nobilis (Phaneropterinae, Tettigoniidae, Orthoptera).

Male and female Elephantodeta nobilis duet with the female responding to the male's long and complex call. The duetting male's call consisted of four parts, described here as parts A, B, C and D. We found that the female replied 570 ms after the male's D pulse, which followed the extended part B and short click of part C. Noncalling males were attracted to the duet and often used satellite tactics by inserting a volley of clicks 200 ms before the alpha male's D pulse. Satellite males used part C of the alpha male song to cue their own call and this inserted call induced females to reply earlier compared with the alpha male call alone. Alpha males often extended their calls with additional D-type calls and so we examined the effectiveness of these calls as countermeasures to satellite calling. There was no influence of this alpha strategy on the satellite's propensity to call although more calls from the alpha male did cause the female to reply more frequently. We also examined the effect of relative intensity of alpha and satellite calls on the female's reply. Reduced satellite intensity increased the variance in the timing of the female response. Finally, we tested the effectiveness of the satellite's call on female phonotaxis within a two-speaker arena. Although females preferred the alpha male they were nevertheless attracted to the satellite calls regardless of the latter's relative intensity. We discuss the possible role of satellite calling as a novel conditional strategy. Copyright 2000 The Association for the Study of Animal Behaviour.

Journal Article↗

CCD-3693: an orally bioavailable analog of the endogenous neuroactive steroid, pregnanolone, demonstrates potent sedative hypnotic actions in the rat.

An endogenous neuroactive steroid, pregnanolone, and an orally available synthetic analog, CCD-3693, were administered to rats at the middle of their circadian activity phase (6 hr after lights off). Electroencephalogram-defined sleep-wake states, locomotor activity and body temperature were concurrently measured 30 hr before and after treatment. Identical procedures were used to test triazolam and zolpidem. Triazolam (0.1-1.6 mg/kg), zolpidem (2.5-10 mg/kg) and the neuroactive steroids (10-30 mg/kg) produced dose-dependent increases in non-rapid eye movement (NREM) sleep. At this dose and time of day (in which the rats were predominantly awake during the 6 hr before treatment) the neuroactive steroids appeared more intrinsically efficacious in promoting NREM sleep than the benzodiazepine ligands. The neurosteroids did not, however, significantly interfere with rapid eye movement sleep and were more selective in reducing (EEG) wakefulness, with relatively less locomotor activity impairment during waking than triazolam and zolpidem. In addition, the benzodiazepine receptor ligands showed distinct "rebound" wakefulness after the NREM sleep-promoting effect subsided, although the neuroactive steroids did not. In addition, in vitro binding studies and in vivo pharmacological data confirmed that CCD-3693 was orally active in standard tests of anxiety, anticonvulsant, loss-of-righting and passive avoidance.

Administration, Oral↗

Save the child's esophagus: management of major disruption after repair of esophageal atresia.

PURPOSE: Given the bias that the native esophagus is the best conduit between the oropharynx and the stomach, the authors report a "conservative" approach to massive esophageal leak, which may be considered "radical" by others. Major disruption of the anastomosis after primary repair of esophageal atresia is a recognized and feared complication. Historically, management has been the performance of cervical esophagostomy and gastrostomy. The aim of this report is to describe the authors' approach to this difficult and serious complication. METHODS: A 15-year retrospective analysis was performed of all patients having esophageal atresia. Data collection focused on the management of all patients with clinically significant esophageal disruption. Radiographically detected (clinically asymptomatic) leaks were managed by continuation of drainage by thoracostomy tubes already in place and are not included. Reoperative thoracotomies were performed, which included primary repair (2), placement of pleural patch alone (2), pleural patch with intercostal muscle flap buttress (2), and operative debridement and drainage alone (1). RESULTS: It was noted that seven patients had clinically significant esophageal disruption requiring reoperation, with circumferential disruptions ranging from 15% to 85%. Presentation included persistent pleural collection (4) and pneumothorax (3). Both patients who underwent primary repair had no evidence of leakage on follow-up esophagograms, neither did one with a pleural patch alone and one with an intercostal muscle flap. Five of the seven patients were tolerating oral feedings at the time of follow-up (range, 6 months to 8 years). One of the two others (both currently inpatients), has a recurrent leak associated with mediastinitis, and the other (who had primary repair) has a presumed neurological impairment of eating. CONCLUSION: Clinically significant disruption of primary esophageal repair should not warrant a cervical esophagostomy and placement of a gastrostomy tube, thus precluding eventual use of the native esophagus. The authors have shown that management by reoperation with primary repair, intercostal muscle flap with or without pleural patch, and/or drainage allows the patient to maintain the native esophagus and yields a generally good outcome after a prolonged healing time.

Esophageal Atresia↗

Tumor necrosis factor and interleukin-6 are not elevated in venous blood from ischemic canine myocardium.

To test the hypothesis that cytokines play a role in ischemic or reperfusion injury, we measured tumor necrosis factor (TNF) and interleukin-6 (IL-6) in pentobarbital-anesthetized dogs before, during, and after coronary occlusion lasting 60 min. Epicardial venous samples from the ischemic (IS) area were compared with nonischemic (NIS) and systemic (SYS) samples. Baseline IS TNF levels were low (2.2 +/- 1.2 U/ml) and not significantly different from NIS and SYS levels. After 50 min of coronary occlusion and at 40 min postreperfusion, IS, NIS, and SYS TNF levels were unchanged. At baseline, IS IL-6 levels were also relatively low (806 +/- 255 U/ml) and not significantly different from NIS and SYS IL-6. Although IS IL-6 increased significantly during coronary occlusion (5682 +/- 1495 U/ml) and reperfusion (10309 +/- 3708 U/ml), NIS and SYS levels were also elevated and did not differ significantly from IS values. The data indicate that TNF and IL-6 are not uniquely elevated in blood from ischemic or reperfused myocardium.

Animals↗

Experimental microsurgical vein grafts: quantitative temporal analysis of progressive media fibroplasia.

The sequential histopathologic changes in microvenous grafts placed in a microarterial system were studied. In 48 Sprague Dawley rats, a 1 cm segment of epigastric vein was interposed into a defect created in the femoral artery. Grafts were explored at 1, 2, 4, and 12 weeks. After an initial smooth muscle hyperplasia, a progressive fibroplasia of the media was observed. Only small focal areas of intimal hyperplasia were seen. The width of the media was measured with an eyepiece micrometer. A statistically significant (P < 0.01) increase in width from 17 microns at 1 week to 462 microns at 12 weeks was noted. Although this process has been described before, this is the first quantitative assessment.

Anastomosis, Surgical↗

The effects of vascularity and cyclosporin A on the mechanical properties of canine fibular autografts.

We studied the biomechanical behavior of orthotopic canine autografts as influenced by vascularized supply and the administration of cyclosporin A at three months and six months post-surgery. The model was the proximal 8 cm of the fibula in young adult dogs. In vascularized grafts, blood supply was re-established by microvascular re-anastomosis. Experimental controls were sham-operated and unoperated bones. Mid-graft test sections were subjected to loading-to-failure in torsion to determine the strength and stiffness. In both three- and six-month groups, vascularized grafts were significantly stronger and stiffer than contralateral nonvascularized grafts. Vascularized grafts were not significantly different from sham-operated bones. A 30-day regimen of cyclosporin A was found to have no measurable effect on mechanical properties for any individual treatment group. The results indicate that re-established blood supply can be a major factor in maintaining the mechanical integrity in large-segment cortical autografts.

Animals↗

Development of collateral circulation in a replanted rat hindlimb model.

The development of collateral circulation was studied in a replanted rat hindlimb model by use of the hemodynamic techniques of hydrogen washout and laser Doppler capillary perfusion monitoring. Collateral development occurred and provided blood flow whose magnitude increased linearly over time. Twenty-seven percent of preligation blood flow was present at 2 weeks after replantation, 39% at 4 to 5 weeks, and 77% at 8 to 9 weeks by laser Doppler assessment. Laser Doppler correlated more closely with limb survival than did the hydrogen washout technique. Uniform necrosis (eight of eight) occurred after pedicle interruption in the 2-week group. Partial limb survival was noted in five of eight replants at 4 to 5 weeks on transection of the vascular pedicle, while complete survival of all replants (nine of nine) was seen at 8 to 9 weeks.

Animals↗

Biological and physical properties of autogenous vascularized fibular grafts in dogs.

The biological and biomechanical properties of normal fibulae, fibulae that had had a sham operation, and both vascularized and non-vascularized autogenous grafts were studied in dogs at three months after the operation. The study was designed to quantify and correlate changes in these properties in orthotopic, stably fixed, weight-bearing grafts and to provide a baseline for additional studies of allografts. The grafts were eight centimeters long and internally fixed. The mechanical properties of the grafts were studied by torsional testing. Metabolic turnover of the grafts was evaluated by preoperative labeling of the dogs with 3H-tetracycline for resorption of bone mineral and with 3H-proline for turnover of collagen. Cortical bone area and porosity were measured. Postoperative formation of bone was evaluated by sequential labeling with fluorochrome. The vascularized grafts resembled the fibulae that had had a sham operation and those that had not had an operation with regard to the total number of osteons and the remodeling process, as measured both morphometrically and metabolically. The vascularized grafts were stronger and stiffer than the non-vascularized grafts and were not different from the bones that had had a sham operation. In contrast, the non-vascularized grafts were smaller, weaker, less stiff, and more porotic, had fewer osteons, and demonstrated increased turnover and resorption compared with the vascularized grafts, the bones that had had a sham operation, and the bones that had not been operated on.

Animals↗

Biology of vascularized bone grafts.

Vascularized canine fibular autografts demonstrated improved biologic and mechanical characteristics 3 months after surgery when compared with nonvascularized controls. The vascularized proximal fibula maintained its overall architecture without bony collapse or significant bone turnover. The strength and stiffness of these grafts were approximately 40 per cent and 56 per cent more than nonvascularized grafts, respectively.

Animals↗

Intravesical methotrexate in the treatment of superficial bladder cancer.

Thirty patients with superficial bladder cancer (Tis, Ta, Tl) difficult to control by endoscopic means were given a total of 49 courses of methotrexate at fortnightly intervals. Four concentrations were investigated. In 14 courses this was the sole treatment and in the remainder the methotrexate was given as prophylaxis. Toxicity was not a problem but in both groups, although there was some evidence of anti-tumour activity, there were high recurrence rates and intravesical methotrexate cannot be recommended.

Carcinoma, Transitional Cell↗

Disseminating the principles of a community support program.

Oregon's Living in the Community (LINC) program for chronic patients succeeds because of effective collaboration between a state hospital and a community treatment and rehabilitation program. The authors trace the development of the LINC program from its beginning in the early 1970s as a progressive retraining project for Eastern Oregon State Hospital's "back ward" patients. They describe principles derived from the original project, such as the provision of training in the patient's natural environment, adoption of these principles into the Oregon community support program, and dissemination of LINC projects to other parts of the state. The authors conclude that such model programs can be transferred to urban and rural settings when supported by a statewide planning effort.

Chronic Disease↗

Application of the training in community living program to rural areas.

In previous work, The Training in Community Living program has been shown to be an effective and feasible mode of community treatment for markedly impaired patients. However, questions have been raised regarding its potential for dissemination to clinical settings in communities other than Madison, Wisconsin. Described are successful experiences in consulting with three rural Wisconsin counties to help them establish community treatment programs modeled on Training in Community Living principles. Also described are the factors responsible for the success of these consultations.

Activities of Daily Living↗

Mobile laboratory for respiratory surveys in industry.

This paper describes the design and performance of a self-contained mobile respiratory laboratory used for the carrying out of complex lung function tests in epidemiological studies of respiratory disease in industry. The laboratory is equipped to perform all conventional lung function tests other than those involving arterial puncture or radioactive isotopes. It has been shown to have a high level of employee acceptability and technical accuracy.

Australia↗