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Biomedical subjects

R C Richter

Publications and source records attributed to R C Richter.

9 recordsLinked to original sources
PubMed1995

Aortic implantation is possible in all cases of anomalous origin of the left coronary artery from the pulmonary artery.

BACKGROUND: Anomalous origin of the left coronary artery from the pulmonary artery (PA) optimally is treated by creation of a multiple coronary system. This study explores the use of aortic implantation employing alternative methods to achieve coronary transfer in all patients, regardless of the site of origin of the anomalous coronary artery, avoiding the problems of bypass grafts and tunnel procedures. METHODS: During the period 1986 to 1994, 11 patients aged 6 months to 8 years (mean age, 2.6 years) underwent repair. Coronary artery origin from the PA included left sinus in 3, posterior in 2, right sinus in 2, intramural aorta with its orifice at the bifurcation of the main and right PA in 1, high left main PA in 1, high at the bifurcation of main and right PA in 1, and anterior in 1. Findings included angina in 4, prior infarctions in 3, ischemia in 7, left ventricular dysfunction in 6, mitral regurgitation in 5, atrial septal defect in 2, and echocardiograms suggestive of endocardial fibrosis in 4. One patient had prior ligation with ventricular dysfunction and collateralization and recanalization. A single patient was asymptomatic. Repair was accomplished by direct transfer using the PA sinus of Valsalva as a button in only 6; tubular reconstruction was used in 4 when the distance was too great to avoid tension; 2 short tubes were constructed with PA wall in 2 of the 3 left sinus origins, whereas 2 long tubes of PA wall were used (1 high on the left side of the main PA and 1 with left anterior descending origin from the anterior sinus of Valsalva in a patient with malrotation [end neo-artery to side aortic reconstruction]); finally, in situ transfer and intraaortic reconstruction (unroofing and anastomosis) was performed in 1 intramural coronary artery. Division of the PA, mobilization of the distal PA, division of the ductus, and direct reanastomosis of the PA was performed in 3 tubular reconstructions, as well as all 6 direct coronary transfers. RESULTS: There were no operative or late deaths. Follow-up of 2 to 100 months (mean, 46 months) revealed no new angina or infarctions, improved function and decreased mitral regurgitation. Echocardiographic and angiographic studies demonstrated patency and prograde flow in the new coronary systems. CONCLUSIONS: Aortic implantation is the treatment of choice for anomalous origin of the left coronary artery. Methods such as direct transfer, tubular reconstruction, and in situ transfer make such implantation possible in all patients regardless of the site of coronary origin, distance from the aorta, or coronary artery configuration.

Anastomosis, Surgical↗
PubMed1991

Evidence for glutamic acid as a possible neurotransmitter between the mesencephalic nucleus cuneiformis and the medullary nucleus raphe magnus in the lightly anesthetized rat.

Previous anatomic and behavioral studies have provided evidence for a strong projection from the mesencephalic nucleus cuneiformis (NCF) to the medullary nucleus raphe magnus (NRM), an area mediating control of a descending pain inhibitory system. Moreover, physiologic experiments in the deeply anesthetized rat have shown that this projection is predominantly excitatory and, at least partially, cholinergic. Recently Fields and coworkers have described 3 physiologically defined classes of neurons in the NRM: the off-, on-, and neutral cells, which exhibit an abrupt pause, increase, or no change in activity, respectively, just prior to the occurrence of the nocifensive tailflick (TF) reflex. The off-cells have been hypothesized as part of a negative feedback system influencing pain transmission at the spinal level. In this study we have examined the interaction between the NCF and neurons in the NRM that were classified as off-, on-, or neutral cells. In addition, since many NCF neurons are glutamatergic, we have examined the possible role of glutamate in the interaction between NCF and NRM. In the lightly anesthetized rat, low-intensity electrical stimulation of NCF excited 53% of NRM neurons at short latencies (mean onset, 3.9 ms), while 20% of NRM neurons were inhibited. Cells of all 3 NRM classes (off-, on-, and neutral) were predominantly excited, an effect which could be blocked by the broad-spectrum excitatory amino acid antagonist kynurenic acid in 36% of cells tested. Pharmacological stimulation of NCF with glutamic acid induced mixed effects, as 34% of NRM cells were excited while 37% were inhibited.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Clinically detectable nerve fiber atrophy precedes the onset of glaucomatous field loss.

Standardized perimetry and nerve fiber layer and color fundus photography were performed annually on 1344 eyes with elevated intraocular pressures. In 83 eyes, glaucomatous field defects developed that met rigid criteria on manual kinetic and suprathreshold static perimetry. Individual nerve fiber layer photographs were read by two masked observers. The more sensitive of the two identified nerve fiber layer defects in 88% of readable photographs at the time field loss first occurred; 60% (6/10) of eyes already had nerve fiber layer defects 6 years before field loss. In contrast, the nerve fiber layer was considered abnormal in only 11% (3/27) of normal eyes and 26% (84/327) of hypertensive eyes. The location of nerve fiber layer and field defects closely corresponded, but nerve fiber layer loss was generally more widespread. Examiner experience and severity of optic nerve damage influenced results. Mild focal defects were more readily recognized than more severe diffuse atrophy. Nerve fiber layer defects expanded with time, often by the development and coalescence of adjacent areas of damage.

Adult↗
PubMed1985

Early infarct expansion: structural or functional?

With the onset of ischemia, the length of myocardial segments increases rapidly, distorting ventricular geometry. Permanent stretching and thinning of infarcted zones have been termed infarct expansion. Although these changes are noted within minutes in vivo, infarct expansion may not be seen for days in postmortem preparations. The apparent postmortem reversal of early infarct expansion suggests that early expansion may be a functional phenomenon, reversible in the early hours of infarction. Alternatively, reversal of expansion may be a postmortem artifact, concealing the importance of underlying structural abnormalities. Myocardial infarction was produced in five dogs by occluding the left anterior descending coronary artery. Ultrasound sonomicrometers were used to measure myocardial segment end-diastolic length in the infarct and normal zones. After 3 hours of ischemia, the heart was arrested in diastole and biopsy specimens were taken from the normal and infarct zones. Sarcomere length was measured from electron photomicrographs, and myofiber width was measured from light photomicrographs. After 3 hours of ischemia, infarct zone segment length had increased significantly more than normal zone length (116 +/- 11 [SD] versus 103 +/- 4% of control length, p less than 0.05), whereas 2 minutes after cardiac arrest, both the infarct and normal zones returned to preischemic segment length, demonstrating apparent reversibility of early infarct expansion. However, histologic study revealed that the infarct zone myofibers were significantly thinner than normal zone myofibers (7.9 +/- 0.3 versus 9.4 +/- 0.3 micron, p less than 0.001) and sarcomere length in the infarct zone was significantly longer than that in the normal zone (1.9 +/- 0.2 versus 1.5 +/- 0.2 micron, p less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Glutaraldehyde-preserved pericardial allografts for pericardial closure.

Repeat cardiac surgery is significantly more difficult than the original surgery. Pericardial closure to limit adhesion formation between the heart and mediastinal structures and thus reduce the increased difficulty of reoperation has been considered. To investigate the feasibility of effecting loose pericardial closure with homologous pericardial grafts, glutaraldehyde-preserved pericardial allografts were implanted in 10 mongrel dogs. After a mean period of 6.7 months (range 6 to 8 months) the grafts were studied grossly and histologically. Adhesion formation was minimal and the adhesions were easily dissectible. The allografts evoked no significant inflammatory response. No infections resulted from graft placement. It is concluded that glutaraldehyde-preserved pericardial allografts may be useful to effect pericardial closure and deserve further investigation in this regard.

Animals↗
PubMed1983

Differential inhibition by aspirin of vascular and platelet prostaglandin synthesis in atherosclerotic patients.

We studied the ability of a single oral dose of aspirin to inhibit prostacyclin synthesis by human arterial and venous tissue and to inhibit thromboxane A2 synthesis by platelets in 70 patients who were undergoing aortocoronary bypass. A dose of 40, 80, or 325 mg of aspirin was administered 12 to 16 hours before surgery. The generation of thromboxane in serum--which provides an estimate of platelet thromboxane production--was reduced from the control value by 77, 95, and 99 per cent after single doses of 40, 80, and 325 mg of aspirin, respectively. By contrast, prostacyclin production in aortic tissue that was removed at operation was reduced by only 35, 38, and 75 per cent, respectively, in response to these doses. Production of prostacyclin in saphenous-vein tissue (not tested after 40 mg of aspirin) fell only slightly and not significantly after 80 mg but was reduced by 85 per cent after 325 mg. These findings indicate that a low dose of aspirin (40 to 80 mg) can largely inhibit platelet aggregation and thromboxane synthesis but has much less effect on prostacyclin production in arterial and venous endothelium.

Administration, Oral↗
PubMedDate not supplied

Family practice residents and the elderly: fostering positive attitudes.

The population of elderly patients is steadily growing. Because physician attitudes toward caring for elderly patients are often negative, it is important to identify aspects of training that lead to favorable attitudes toward the practice of geriatrics. This study investigated the relationships among past casual experiences, educational experiences, level of training, faculty attitudes, and current resident attitudes. All Louisiana family practice residents (72) and program faculty members (35) were surveyed, with response rates of 69% and 86%, respectively. Residents generally held positive attitudes toward the elderly. Variables associated with positive resident attitudes were the amount of didactic training and faculty attitudes. No differences were found among the attitudes of residents at different levels of training. These findings highlight the importance of cognitive training and role modeling in geriatrics. Educational settings in which training occurs--classrooms, ambulatory care facilities, hospitals, and nursing homes--deserve careful consideration.

Aged↗