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Biomedical subjects

M E Chapman

Publications and source records attributed to M E Chapman.

12 recordsLinked to original sources
PubMed2001

Pulmonary wedge pressures confirm pulmonary hypertension in broilers is initiated by an excessive pulmonary arterial (precapillary) resistance.

High retrograde pressure through the pulmonary venous system caused by failure of the left ventricle or left atrio-ventricular valve may result in the elevated pulmonary arterial pressure and right ventricular hypertrophy associated with pulmonary hypertension syndrome (PHS; ascites) in broiler chickens. In the present study, unanaesthetized male broilers from an ascites-resistant line, the base population from which the resistant line was derived, and a separate unselected line were used to determine whether changes in wedge pressure (thought to be similar to left atrial pressure) are predictive of differences in the pulmonary arterial pressure of clinically healthy and pre-ascitic broilers. Venous, right atrial, right ventricular, pulmonary arterial, and wedge pressures were obtained by inserting a catheter into a wing vein and progressively advancing the catheter into a pulmonary branch artery until the catheter tip became wedged in and occluded the flow through a terminal artery. Mean right ventricular and pulmonary arterial pressures were lower in the resistant line than in the base population, but wedge pressures did not differ between the resistant, base, and unselected lines. Right:total ventricular weight ratios (RV:TV) and the percentage saturation of hemoglobin with oxygen in arterial blood ranged in value from 0.18 to 0.44 and 65 to 96%, respectively. Wedge pressure, however, remained similar when pre-ascitic broilers with high RV:TV values and low oximetry values were compared with clinically healthy broilers. In all birds, whether healthy or showing pre-ascitic characteristics, the wedge pressure was slightly higher than the right atrial pressure but substantially lower than pulmonary arterial pressure. These observations provide definitive proof that pulmonary hypertension is initiated as a consequence of excessive pulmonary arterial or arteriole resistance. Pulmonary venous pressure is estimated by measuring the pulmonary arterial wedge pressure, and high wedge pressures would be evident if pulmonary hypertension was caused by the elevated downstream resistances associated with left-sided heart failure.

Animals↗
PubMed2001

Intravenous endotoxin triggers pulmonary vasoconstriction and pulmonary hypertension in broiler chickens.

Bacterial endotoxins stimulate endothelin-mediated, thromboxane-dependent increases in pulmonary vascular resistance in mammals, and thromboxane has been shown to cause an immediate but transient pulmonary vasoconstriction in broiler chickens. In the present study, i.v. injections of 1 mg endotoxin into anesthetized male broilers caused a pulmonary vasoconstrictive response that was delayed in onset by 15 min and that elevated the pulmonary arterial pressure by 10 mm Hg within 25 min postinjection. Thereafter, pulmonary hemodynamic variables gradually (> or = 15 min) returned toward pre-injection levels, and supplemental injections of 4 mg endotoxin during this recovery period failed to reinitiate pulmonary hypertension. In contrast, injecting the thromboxane A2 mimetic U44069 during the endotoxin recovery period triggered pulmonary vasoconstriction and pulmonary hypertension similar in magnitude to the responses triggered by U44069 before endotoxin had been administered. The time course and magnitude of the pulmonary hemodynamic responses to endotoxin were highly variable among individual broilers, whereas the individual responses to U44069 were more consistent. Unanesthetized broilers resembled anesthetized broilers in the time course, magnitude, and variability of their pulmonary hemodynamic responses to endotoxin. Overall, these observations are consistent with the hypothesis that endotoxin initiates a biochemical cascade, culminating in the delayed onset of pulmonary vasoconstriction and pulmonary hypertension within 20 min postinjection. Subsequently, the pulmonary vasculature remains responsive to large bolus injections of exogenous thromboxane mimetic; however depletion of endogenous vasoconstrictive components of the endotoxin-mediated cascade, a compensatory increase in endogenous vasodilators, or the induction of a transient cellular tolerance to endotoxin prevented fourfold higher doses of endotoxin from reversing the return toward a normal pulmonary vascular tone. Individual differences among broilers in their susceptibility to pulmonary hypertension syndrome (ascites) may be related to innate or acquired variability in their pulmonary vascular responsiveness to vasoactive mediators.

Animals↗
PubMed1995

Does pulmonary hypertension syndrome (ascites) occur more frequently in broilers medicated with monensin?

The performance of broilers reared in floor pens and given monensin in the feed at 121 ppm was compared with that of birds given no drug. Feed intake and BW gain of medicated birds was significantly lower than that of unmedicated birds from 0 to 22 d of age. Feed intake and feed conversion of medicated birds was significantly reduced, compared with unmedicated birds, from 22 to 53 and 0 to 60 d of age. Total mortality, and mortality due to leg abnormalities from 22 to 53 and 0 to 60 d, was significantly lower in birds given monensin. There was no difference in the incidence of tibial dyschondroplasia (TD) by 60 d. No differences in mortality due to pulmonary hypertension syndrome (PHS) were observed for any age period. Birds removed from pens at 28 d that had received monensin had lower hematocrit and percentage saturation of hemoglobin with oxygen in the blood than unmedicated birds. No differences in these variables were found at 54 d. There were no differences in the right ventricle weight: total ventricular weight ratios or electrocardiogram lead II values at 28 or 54 d. The results indicate that PHS does not occur more frequently in broilers medicated with monensin.

Animals↗
PubMed1994

A prospective analysis of incidental paranasal sinus abnormalities on CT head scans.

A prospective analysis of the incidence of paranasal sinus opacification in 100 patients referred for cranial computerized tomography (CT) for non-sinus related problems is described. The findings were correlated with symptomatic assessment. Twenty-seven per cent of asymptomatic patients had sinus opacification. The study illustrates the importance of careful clinical correlation when interpreting CT scans of the paranasal sinuses.

Adolescent↗
PubMed1993

Sedation and patient monitoring in vascular and interventional radiology.

A postal survey of British and Irish interventional radiologists was carried out in 1991 in order to assess current practice with respect to sedation and monitoring of patients during angiography and interventional procedures. The response rate was 65%. 49% of patients are fasted prior to angiography and 68% prior to interventional procedures. Radiologists participate in obtaining consent in 60% of cases. Patients are often (50%) sedated for angiography and usually (62-94% depending on the procedure) sedated for interventional procedures. Nurses are present for most procedures, but are given the task of monitoring the patient's vital signs in only 49% of cases. Anaesthetists are present for less than 10% of interventional procedures. Pulse oximetry is used routinely in 20% of departments, and automatic blood pressure monitors in 16%. 28% of radiologists never administer oxygen to patients under sedation, whereas 4% always do. 43% of departments have a staffed recovery area. Most vascular/interventional suites are stocked with emergency drugs and 80% with a defibrillator. 28% of departments report at least one death during or shortly after a procedure during the last 10 years. 18% of interventional radiologists have taken a refresher course in cardiopulmonary resuscitation in the past year. These findings indicate a wide variation in practice and a need to standardize practice at a uniform high level.

Analgesia↗
PubMed1993

Closed intramedullary femoral osteotomy. Shortening and derotation procedures.

Closed osteotomy and nailing were performed on 37 patients for leg-length inequality or rotational deformities. Shortening operations were performed in 31 patients, derotation in six. Preoperatively, the leg-length discrepancy ranged from 2 to 6.6 cm. All femoral shortenings resulted in correction to less than 1 cm. Preoperatively, rotational deformities averaged 58 degrees; all were corrected to within 5 degrees of normal. Follow-up observation averaged 3.3 years. There were no nonunions or infections. All patients regained preoperative joint range of motion (ROM). Thirteen patients were Cybex tested one year or more postoperatively; all had quadriceps and hamstring strength equal to or greater than the contralateral leg, except for two patients who had suffered additional trauma to the shortened femur. Closed femoral osteotomy is an effective, safe, and reproducible means to obtain lower limb length correction in patients with leg-length inequality or rotational abnormality.

Adolescent↗
PubMed1992

Sources of noradrenergic afferents to the hypoglossal nucleus in the rat.

The sources of noradrenergic (NA) innervation to the hypoglossal nucleus (nXII) in the rat were investigated with double-labeling histochemical/immunocytochemical and lesion/degeneration techniques. Following injection of wheat germ-agglutinin conjugated to horseradish peroxidase into nXII, brain stem sections were reacted with tetramethylbenzidine, stabilized, and incubated in antiserum to tyrosine hydroxylase (TH). Double-labeled neurons were observed in three pontine sites bilaterally, although mainly ipsilaterally, that included the nucleus subceruleus (nSC; 68.75%) and the A7 (21.09%) and A5 (10.15%) cell groups. Confirmation of the above results and identification of the course taken by descending NA-nXII projections was accomplished by lesioning the rostral pons, the nSC, or the medullary catecholamine bundle (MB), the suspected route by which NA afferents reach nXII. Quantitative estimates of the reduction of TH immunoreactivity on the lesioned compared to nonlesioned side of nXII were made densitometrically. In each case, TH immunostaining was significantly decreased (75%) in the ipsilateral caudoventromedial district of nXII, the predominant target area of NA input. The results from this study establish that multiple NA sources in the pons project to nXII in the rat, the majority of NA-nXII afferents are derived from the nSC, and descending NA-nXII projections course in the MB. These data are discussed relative to tongue control.

Afferent Pathways↗
PubMed1991

Use of percutaneous nephrostomy in malignant ureteric obstruction.

Seventeen patients with malignant disease underwent percutaneous nephrostomy to relieve renal failure secondary to ureteric obstruction. Renal function improved in 88%. The median survival time was 18 weeks and 58% left the primary hospital to return home or to a terminal care hospice. Minor complications occurred in 58%. The use of bilateral nephrostomy tubes conferred no greater benefit than a unilateral tube. Intervention in malignant ureteric obstruction may confer some benefit and should not necessarily be viewed with pessimism.

Acute Kidney Injury↗