PubMed Health⌕ Search

Biomedical subjects

J C Austin

Publications and source records attributed to J C Austin.

At least 37 records · Page 2Linked to original sources
PubMed1988

Thromboxane synthetase inhibition reduces ventricular irritability after coronary occlusion and reperfusion.

Reperfusion of ischemic tissue is responsible for production of metabolites with deleterious local vascular effects. Thromboxane A2, a potent vasoconstrictor and platelet aggregator, has been implicated as a mediator of the "reperfusion injury." We studied the effect of an experimental thromboxane synthetase inhibitor, OKY-046, on coronary sinus thromboxane levels, ventricular irritability, myocardial contractility, infarct salvage, and histologic features of reperfusion. Sixteen sheep were randomized to OKY-046, 3 mg/kg, or saline vehicle before 3-hour occlusion and subsequent reperfusion of the left anterior descending artery. The OKY group demonstrated less ventricular irritability as measured by incidence of ventricular fibrillation and necessity for countershock to reverse tachyarrhythmias. Coronary sinus thromboxane levels were significantly lower in the OKY group compared with the control group. There is additional evidence to suggest that OKY increases infarct salvage and attenuates histologic features of microcirculatory damage.

6-Ketoprostaglandin F1 alpha↗
PubMed1988

Vaterian cancer in siblings.

The simultaneous occurrence of Vaterian carcinoma in two siblings suggests a genetic influence in their pathogenesis. Their classic clinical presentation of obstructive jaundice and weight loss required pancreaticoduodenectomy for this neoplasm. Pedigree analysis revealed a third sibling who died from an unresectable periampullary malignancy. Neither of the probands exhibited, as late as the seventh decade, evidence compatible with a diagnosis of familial polyposis coli or Gardner's syndrome. Flow cytometry studies revealed an aneuploid distribution in one tumor and tetraploid in the other. The rarity of this neoplasm, in the absence of contributing epidemiologic factors, suggests that this is a pleotrophic manifestation of a cancer-prone genotype.

Adenocarcinoma↗
PubMed1988

Comparison of performances of students in programs at LSU Medical School in Shreveport.

The purpose of the study reported here was to evaluate the performance of graduates of the accelerated six-year (combined B.S.-M.D. degree) program and compare it with that of graduates following the regular curriculum at the Louisiana State University School of Medicine in Shreveport. Cumulative medical school grade-point averages, scores on the Federation Licensing Examination, and failure rates for the two groups were compared; by these criteria, the six-year graduates performed adequately but not as well as expected from their high school credentials (the basis for their entry into the accelerated program). Advantages and disadvantages of the six-year program are discussed with respect to the students, the medical school, and the undergraduate college of LSU at Shreveport.

Curriculum↗
PubMed1987

Neuroradiologic evaluation of sacral abnormalities in imperforate anus complex.

Neurologic impairment and sacral spinal anomalies are a finding in children with imperforate anus. The neurologic deficits previously had been considered static rather than progressive. Recent experience at this institution has documented the frequent association of imperforate anus patients having bony sacral and other spinal deformities with progressive neurologic dysfunction. These deficits are related to underlying spinal cord anomalies, which may be amenable to neurosurgical correction. To investigate the nature and frequency of such lesions, spinal cord imaging was done in these patients. From July 1976 to June 1985, 106 patients with imperforate anus were screened with plain radiographs of the sacral spine; 37 (35%) patients had abnormalities. Of these, 26 have been evaluated with a variety of spinal cord imaging techniques, including magnetic resonance imaging (18), digital metrizamide myelotomography (14), computed tomography (10), metrizamide myelography (5), or ultrasound (4). Four patients were lost to follow-up, and seven have not yet been studied. Fifteen of the 26 patients (53%) had one or more abnormal studies. Thirteen were considered to have progressive dysfunction with operable lesions and have undergone neurosurgical correction. At follow-up, there was improved leg function in five patients and improved bladder function in two patients. No patient had additional neurologic deficits after surgery. Because of the high incidence of progressive but potentially correctable myelodysplasias in patients with coexisting anorectal and sacral anomalies, routine radiographic screening of the spine is recommended, followed by spinal cord imaging and neurosurgical evaluation if warranted.

Abnormalities, Multiple↗
PubMed1987

Blood gas pH and pulmonary response to the inhalation of low osmolar contrast media iopamidol and ioxaglate.

Effects of inhalation of diluted low-osmolar ionic ioxaglate and nonionic iopamidol 200 water-soluble radiographic contrast media on neonatal pig lung were evaluated. Our purpose was to assess the suitability of these substances for the radiologic investigation of upper gastrointestinal problems in human neonates in whom aspiration may occur. We used two-week-old baby piglets weighing 2.5-3.5 kg as the experimental model because they are similar in weight and size to a human neonate. The effects of intratracheal instillation of isosmolar contrast media were evaluated using the parameters of (1) blood gas exchange, (2) clinical status, (3) radiology, and (4) histopathology. The piglets showed no clinical or radiologic abnormality; blood gas exchange, initially impaired, rapidly returned to normal. Long-term (four days) follow up showed mild, self limiting but persistent infiltrates in the lungs at histology. We conclude that these diluted contrast media are suitable for upper gastrointestinal examination in neonates.

Administration, Inhalation↗
PubMed1987

Fixation of vervet monkey oral mucosa for ultrastructural investigation--TEM.

This study was undertaken to determine optimal fixation procedure for vervet monkey (Cercopithecus pygerythrus) oral mucosa. Perfusion and immersion fixation were investigated using glutaraldehyde and glutaraldehyde-paraformaldehyde fixatives with either a phosphate or sodium cacodylate buffer as vehicle and with osmolarities varying from 2010 to 320 mosm. Good fixation could not be obtained uniformly or consistently by perfusion. Vervet monkey oral mucosa is best fixed by first perfusing the head and neck of the animal with 250-500 ml 0.9% saline containing Procaine-HCl and heparin, followed by decapitation and immersion of the head in a 2.5% glutaraldehyde: 2% paraformaldehyde: 0.02 M sodium cacodylate buffered fixative (900 mosm) at 4 C for 24 hr.

Animals↗
PubMed1987

Effect of total spinal anesthesia on arterial and venous responses to dopamine and dobutamine.

To test whether acute denervation alters the vascular effects of dopamine and dobutamine, we anesthetized 16 greyhounds and placed them on total cardiopulmonary bypass (CPB). Eight dogs received total spinal anesthesia before drug testing; eight dogs were tested in the absence of total spinal anesthesia. During dopamine and dobutamine infusions, venous capacitance [determined by the volume of the CPB venous reservoir (VR)] and mean arterial pressure (MAP) were monitored. The CPB pump flows remained constant throughout our studies. Every dog received six increasing doses of both drugs. In the absence of total spinal anesthesia, both dopamine and dobutamine increased VR (decreased venous capacitance) in a dose-dependent manner. Dobutamine decreased MAP in a dose-related fashion but dopamine had no significant effect on MAP. After total spinal anesthesia, both dopamine and dobutamine produced greater dose-related increases in VR (i.e., decreases in venous capacitance) than in the absence of spinal anesthesia. Dopamine increased MAP but dobutamine had no significant effect. These data demonstrate how dopamine and dobutamine differ in their effects on the arterial circulation in the presence or absence of spinal anesthesia. The acute denervation of spinal anesthesia altered venous and arterial dose-response relationships of both drugs. Finally, our study demonstrates the effectiveness of dobutamine and, perhaps even more so, dopamine as possible alternatives to ephedrine for the pharmacologic correction of the noncardiac circulatory sequelae of spinal anesthesia.

Anesthesia, Spinal↗
PubMed1986

Treatment of esophageal cancer: the continued need for surgical resection.

We conclude that preoperative radiotherapy and chemotherapy is very likely to improve the length of survival in patients with squamous cell carcinoma undergoing surgical resection and decreases the incidence of symptomatic local recurrence requiring additional palliative treatment. A favorable tumor response to adjuvant therapy, however, did not significantly improve the survival curves in our study, does not guarantee complete tumor regression, and should not be cited as a basis for elimination of esophagectomy in treatment protocols. Adenocarcinoma treated with surgical resection has a better prognosis than similarly treated squamous cell carcinoma, but has a poorer prognosis than squamous cell carcinoma treated with preoperative adjuvant therapy and surgical resection.

Actuarial Analysis↗
PubMed1986

Inotropic response of the salvaged myocardium after acute coronary occlusion.

We determined the response of the reperfused myocardium to inotropic stimulation with dobutamine hydrochloride. The middle part of the left anterior descending coronary artery (LAD) was occluded in 15 greyhounds for 3 hours. Group 1 (N = 8) was reperfused for 3 hours in the beating, working heart. Group 2 (N = 7) was put on cardiopulmonary bypass (CPB) for 1 hour, received 500 ml of potassium cardioplegia in the aortic root and in the area of ischemia through an internal mammary-LAD graft, and the LAD was reperfused off CPB for 3 hours. After 3 hours of reperfusion, dobutamine was given at 10 micrograms/kg/min for 20 minutes. Regional myocardial function was determined with subendocardial ultrasonic crystals in the area of ischemia and in the base of the heart; segmental contractility was determined from the ratio of peak left ventricular pressure to end-systolic segment length; and global contractility was determined by the slope of the ventricular pressure wave at a developed pressure of 40 mm Hg. Measurements were made prior to LAD occlusion (control), at the end of 3 hours of reperfusion (6 hours from the beginning of occlusion), and after 20 minutes of dobutamine infusion. Dobutamine infusion improved segmental function in all animals compared with 3 hours of reperfusion. The study shows that the reperfused myocardium responds favorably to inotropic stimulation after 3 hours of occlusion and 3 hours of reperfusion, and that the contractile response both to reperfusion and to inotropic stimulation is greatly affected by the method of reperfusion.

Animals↗
PubMed1986

Pulpal responses to amalgam restorations in cavities with and without smear layer removal.

A conventional low copper amalgam was placed in cavities with and without smear layer removal and the amalgam restorations were covered with a resin overlay. The restored teeth were retrieved at 2, 28 and 56 days postoperatively in order to test for leakage and then pulpal reactions. More inflammation was seen in the teeth from which the smear layer had been removed. Abscesses were present in 6 teeth at 28 days but only one was associated with demonstrable bacteria. This study does not support smear layer removal before insertion of low copper amalgam restorations.

Animals↗
PubMed1985

The pulpal response to dilute citric acid smear removers.

The aim of this study was to determine the pulpal response to three dilute citric acid smear removers. Forty-eight vervet monkeys (Cercopithecus aethiops pygerythrus), in three groups of sixteen animals provided 384 tooth specimens for the histological evaluation of the pulpal response at 3, 31, and 59 days post-operatively. Labial Class V cavities were prepared in the maxillary and mandibular incisor teeth. The pulpal responses elicited by 1% aqueous citric acid, 1% citric acid in 30% ethanol and 0.1% citric acid in 30% ethanol solutions, in unlined cavities and in cavities lined with Dycal after acid application, were compared with those elicited by a negative control material--(Nobetec), and a positive control material--(Syntrex). Using Stanley's criteria the most severe pulpal responses were seen in teeth treated with 1% aqueous citric acid and 1% citric acid in 30% ethanol without a subsequent liner, and by Syntrex at all three time intervals. The use of Dycal as a liner after smear removal markedly reduced the pulpal responses.

Acid Etching, Dental↗
PubMed1985

Early and late risk of mitral valve replacement. A 12 year concomitant comparison of the porcine bioprosthetic and prosthetic disc mitral valves.

A consecutive series of 706 mitral valve replacements was performed from January, 1972, to January, 1984. The follow-up ranged from 6 to 150 months with a mean of 50 and a median of 43 months. Seven percent (50) of the patient were lost to follow-up. There were 243 men and 463 women, whose ages ranged from 17 to 86 years (mean 58). A porcine bioprosthetic valve was implanted in 528 patients (514 Hancock and 14 Carpentier-Edwards valves) and a prosthetic disc valve in 178 patients (102 standard disc Björk-Shiley, 34 Beall, and 42 Harken disc valves). Seven patients were in Functional Class II, 325 in Class III, and 374 in Class IV. A concomitant operative procedure was performed in 253 of the 706 patients (36%). Mitral regurgitation was the primary hemodynamic lesion in 363 and mitral stenosis in 343. Operative mortality figures were as follows: 77 of 706 (11%) for the overall group, 34 of 453 (7.5%) for isolated mitral valve replacement, 30 of 169 (17.5%, p = 0.001) for mitral replacement plus coronary bypass, 49 of 528 (9%) for the bioprosthetic valve group, and 28 of 178 (16%) for the prosthetic disc valve group (p = 0.01). After the operation, 262 patients were in Functional Class I, 99 in Class II, and 18 in Class III. The long-term survival rate was significantly lower in patients who had an associated procedure (45% +/- 6%), who had mitral regurgitation rather than mitral stenosis (53% +/- 5% versus 67% +/- 4%) (p = 0.002), who were in Functional Class IV rather than Classes I to III (51% +/- 4% versus 70% +/- 4%) (p = 0.001), and who received a prosthetic disc valve rather than a bioprosthesis (40% +/- 6% versus 67% +/- 4%) (p = 0.001). Thromboembolic rates were significantly higher with prosthetic valves than with bioprosthetic valves (4.6% +/- 0.22% versus 2.4% +/- 0.5% per patient-year of follow-up), and the incidence of anticoagulant-related hemorrhage was significantly higher in the prosthetic valve group (1.65% versus 0.43% per patient-year). Primary valve dysfunction was significantly more common in the bioprostheses (1.23% versus 0.40% per patient-year).(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1983

Scanning electron microscope observations on the tubule content of freeze-fractured peripheral vervet monkey dentine (Cercopithecus pygerythrus).

Pulp tissue in the incisors was fixed in situ by perfusion. Cervical thirds of the tooth crowns were excised by sectioning the teeth transversely and cryofractured through the long axis of the tooth in a bucco-lingual mid-axial plane to expose the dentine from the pulp to the enamel-dentine junction. Specimens were freeze-dried and the fracture surfaces examined by scanning electron microscopy. Flattened tubular processes were noted protruding from the open ends of transversely fractured dentinal tubules in the outer third of the dentine. These structures were present in fractured tubules to within 20 microns of the enamel-dentine junction. These observations suggest that odontoblast processes traverse the full length of dentinal tubules.

Animals↗
PubMed1983

Pulpal responses evaluated by two assessment systems. Use of Nobetec as negative and Super-Syntrex as positive control materials.

In the assessment of pulpal responses to dental materials there is no general agreement regarding which system should be used in the selection of histologic sections for assessment and which negative and positive control materials should be used. The present study is an evaluation, on 227 sections, of two pulpal assessment systems and three section-selection methods using a negative (zinc oxide and eugenol cement) and a positive (silicate) control material. The results indicate that, depending on which system is used, considerable variation in response can be noted. Better standardization of methods is necessary.

Animals↗