Biomedical subjects
Publications and source records attributed to D G Ritter.
Nine Alaskan wolves (Canis lupus) were found dead during spring and summer 1985; five of seven animals tested for rabies virus were positive. The 1985 epizootic altered annual den use patterns by wolves in northeastern Alaska, but did not appear to affect population size. We propose that rabies in arctic wolves may be more common than previously thought.
Arctic foxes were immunized with the SAG1 oral rabies vaccine. The effectiveness was determined by the serological response and by the survival to a challenge dose of rabies virus from an Alaskan fox. Vaccine virus was isolated from saliva 1 h after the liquid vaccine was placed directly into the mouth but not subsequently (tested up to 1 week postvaccination). Two weeks after vaccination, protective antibody levels were present in all foxes and all vaccinated foxes survived challenge at 9 weeks postvaccination. At 26 weeks postvaccination (17 weeks postchallenge) all but one fox had detectable antibody levels. Neural tissue harvested from surviving foxes was negative for rabies virus by direct immunofluorescent testing. One of the foxes vaccinated with SAG1 seroconverted and survived challenge even though the titre of the vaccine used was almost 4 logs less than that used to vaccinate the other foxes. These results suggest that the avirulent SAG1 oral rabies vaccine is very effective in protecting arctic foxes.
The bluetongue virus core particles have been shown to contain an RNA-directed RNA polymerase (1). To identify the protein responsible for the virion RNA polymerase activity, the complete 3.9 Kb DNA clone representing the largest RNA segment 1 (L1) of bluetongue virus (BTV-10) was placed under control of the polyhedrin promoter of Autographa californica nuclear polyhedrosis virus (AcNPV). The derived recombinant virus was used to infect Spodoptera frugiperda cells. As demonstrated by stained polyacrylamide gel electrophoresis and by the use of bluetongue virus antibody, infected insect cells synthesized the largest protein of BTV-10 (VP1, 150 k Da). Antibody raised in rabbit to recombinant VP1 protein recognized bluetongue virus VP1 protein. The recombinant virus infected cell lysate had significantly inducible levels of RNA polymerase enzymatic activity as determined by a poly (U)-oligo (A) polymerase assay. The availability of enzymatically active bluetongue virus RNA polymerase provides a system in which we can precisely delineate the role this protein plays in the regulation of bluetongue replication.
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Full-length DNA clones representing the 10 double-stranded RNA segments of US bluetongue virus serotype 10 (BTV-10) have been used in a study to determine the genetic relationships among 20 different BTV serotypes. The study was undertaken using Northern blot hybridization techniques involving 32P-labelled DNA probes and total RNA species extracted from BHK-21 cells infected with 20 different BTV serotypes. The results obtained indicate that all the genes representing the nonstructural proteins of BTV (NS1, NS2 and NS3) as well as most of the inner capsid polypeptides are highly conserved (e.g., VP1, VP3, VP4), while VP6 and VP7, the remaining two inner capsid components, are less conserved. The genes representing the two outer capsid polypeptides, VP2 and VP5, vary significantly. When complete DNA clones of RNA segment 2 (representing the VP2 neutralization gene) of 4 other US serotypes (BTV-2, -11, -13 and -17) and one Australian serotype (BTV-1) were used in similar hybridization studies, the data obtained showed that despite geographical distances, a certain BTV serotype exhibits similarities. Some hybridization signals were detected with several of the inner capsid genes and the corresponding RNA segments of epizootic hemorrhagic disease virus (EHDV), a distantly related orbivirus, although none of the BTV outer capsid genes, nor any of the nonstructural genes hybridized with either EHDV-1 or EHDV-2 RNA species.
Arctic foxes (Alopex lagopus) were successfully immunized against rabies using an orally-administered, liquid SAD-BHK21 live virus vaccine in a sausage bait. Immunization was determined by serologic response and by resistance to challenge with an arctic rabies virus strain. Virus was not shed in saliva following oral vaccination, indicating that arctic foxes would not infect other foxes after ingesting this vaccine. High antibody levels were present in all experimental foxes 2 wk following initial vaccination. A booster vaccination at 56 wk induced a significant serologic response within 1 wk, suggesting an anamnestic response but titers began to decline within 8 wk in most foxes. Foxes were observed for 16 mo following the challenge and exhibited no symptoms of rabies. The SAD-BHK21 rabies vaccine in a sausage bait system has a strong potential for vaccinating wild populations of arctic fox.
UNLABELLED: We examined the cases of 702 patients found to have isolated atrial septal defect of the secundum or sinus venosus type at catheterization from 1953 to 1978. Forty patients (6%), 34 women and six men, had pulmonary vascular obstructive disease, with a total pulmonary resistance greater than 7 U/m2; of these patients 26 (mean age 47 years) underwent surgical closure and 14 (mean age 44 years) received medical treatment. All patients were followed for at least 4 years, with a median follow-up of 12 years. At the most recent follow-up, 17 of the 40 patients were dead. Of the 22 surgically treated patients with total pulmonary resistance less than 15 U/m2, 19 were alive with significant regression of symptoms. All four surgically treated patients with total pulmonary resistance greater than or equal to 15 U/m2 were dead. Of the five medically treated patients with total pulmonary resistance less than 15 U/m2, four had died, and one was alive with significant progression of symptoms. Of the nine medically treated patients with total pulmonary resistance greater than or equal to 15 U/m2, six had died and the three survivors had progression of symptoms. In the surgically treated group, the following variables correlated with survival: total pulmonary resistance (p less than .00001), pulmonary arteriolar resistance (p less than .00001), pulmonary-to-systemic resistance ratio (p = .004), systemic arterial oxygen saturation (p = .005), and pulmonary arterial oxygen saturation (p = .007). IN CONCLUSION: (1) Atrial septal defect with high total pulmonary resistance is uncommon and predominates in adult female patients.(ABSTRACT TRUNCATED AT 250 WORDS)
Six arctic foxes (Alopex lagopus) were marked with iophenoxic acid (IA), a substance which elevates concentrations of protein-bound iodine in blood plasma. Buccal absorption of IA was determined by placing 20 mg IA dissolved in 100% ethyl alcohol on the tongue. Blood samples collected from 1 to 36 wk following exposure showed that all foxes were marked already at 1 wk and continued until 13 wk; two foxes were still marked at 36 wk. Clearance rates for iodine varied with initial dose response, and those foxes with high 1-wk iodine concentrations excreted iodine more rapidly than those with lower initial concentrations; by 13-wk excretion rates were similar.
Tissue-valved prosthetic extracardiac conduits fail in 6% to 30% of patients within 5 years of implantation. Failure is caused both by valve degeneration and by conduit peel formation. This report describes a technique, performed in 16 children, in which an obstructed right ventricle-to-pulmonary artery valved conduit was removed and a new conduit constructed using the conduit bed as the posterior wall and a patch of xenograft pericardium (n = 10), homograft dura mater (n = 5), or Dacron (n = 1) as the roof of the conduit. One child with pulmonary hypertension required a Björk-Shiley pulmonary valve; in the others no valve was inserted. This technique simplifies conduit replacement, allows for a generous-sized outflow tract that may grow with patient growth, and uses material unlikely to become obstructed.
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Two patients who had univentricular heart presented with complaints of recurrent nausea and vomiting during exertion. Exercise study revealed 1:1 atrioventricular conduction and no symptoms at rest; at peak exercise, both patients experienced progressive, high grade, second degree atrioventricular block and nausea. Both patients underwent permanent pacemaker implantation, with relief of symptoms. Exercise testing is important in evaluating patients who are at increased risk of spontaneous atrioventricular block, and exertion-induced nausea may be a clue to its presence.
Limited information is available concerning the long-term survival of patients with atrioventricular discordance, ventriculoarterial discordance, and two ventricles (corrected transposition). The long-term follow-up of 107 patients examined at the Mayo Clinic over a 30-year period between 1951 and 1981 was reviewed. Overall survival from the date of Mayo Clinic diagnosis was 70% at five years and 64% at ten years. Associated variables were analyzed for their effect on survival including sex, age at diagnosis, presence of ventricular septal defect, pulmonary stenosis, dextrocardia, left atrioventricular valve insufficiency, and complete heart block. There was no significant difference between those with and without a ventricular septal defect (VSD). Pulmonary stenosis was protective when a VSD was present but was not a significant predictor of long-term survival. The only variable that consistently correlated with decreased survival was left atrioventricular valve insufficiency (p less than 0.04 for univariate and stepwise Cox, and p = 0.08 for multivariate analysis). A logistic model for survival after open-heart surgery failed to identify any significant variable. We conclude that the presence of left atrioventricular valve insufficiency in association with atrioventricular discordance significantly alters the long-term outcome. Atrioventricular valve replacement should be considered in such patients when insufficiency becomes hemodynamically significant.
From 1965 until March, 1982, 167 patients underwent surgical repair of truncus arteriosus. The age at operation ranged from 18 days to 33 years (mean 6 years). There were 48 hospital deaths (28.7%). The following factors had a positive correlation with the possibility of a surgical death: age at operation less than 2 years (p less than 0.001), a postrepair pulmonary arterial/left ventricular pressure ratio greater than 0.5 for patients with two pulmonary arteries (p less than 0.001) and greater than 0.6 for patients with unilateral absence of a pulmonary artery (p less than 0.02), and a postrepair right ventricular/left ventricular pressure ratio greater than 0.8 (p less than 0.008). The 119 hospital survivors were followed up for a total of 829 person-years. Late survival rate at 5 years was 84.4% and at 10 years, 68.8%. Preoperative factors that correlated with a reduced long-term survival rate were as follows: increasing age at operation (p = 0.004), the presence of moderate or severe truncal valve insufficiency (p = 0.008), lower pulmonary/systemic flow ratio (p = 0.04), and unilateral absence of a pulmonary artery (p less than 0.001). Thirty-six patients required reoperation during the follow-up period (30%) primarily for replacement of the right ventricular-pulmonary arterial conduit and/or for truncal valve replacement. The long-term results obtained in these patients support the need for early repair of the anomaly, improvement in the methods for control or repair of the truncal valve insufficiency, and the continued search for better extracardiac valved conduits.
The presence of unrecognized partial anomalous pulmonary venous connection may cause complications of pulmonary infarction and right-to-left shunting in patients undergoing the modified Fontan procedure. These complications can be prevented by identification of any anomalous pulmonary venous connection at preoperative cardiac catheterization.
Data are presented from 84 patients (45 males, 39 females), aged 6 days to 25 years (mean 10 years), with univentricular heart who underwent a palliative surgical procedure. The mean follow-up period was 5 years (range 1 month to 25 years). Of the 84 patients, 33 died and 51 are alive. The survivors were 1.5 to 41 years (mean 15). Systemic pulmonary artery shunts alone were performed in 43 patients, pulmonary artery banding in 15, and a combination of procedures in 26. Five years after diagnosis, 70% of patients with type A and 54% with type C univentricular heart were alive, with no statistical difference in survival between the patient groups. Because of the high attrition rate in these patients despite palliation, further attempts to perfect corrective surgery appear justified.
Type A univentricular heart is a severe congenital cardiac defect; 50% of patients are dead 14 years after diagnosis, a death rate of 4.8% per year. Type C univentricular heart is even more lethal; 50% of patients are dead 4 years after diagnosis. Pulmonary stenosis did not protect either group of patients in terms of overall survival. Of the patients in class I or II at initial diagnosis, 34% of patients with type A and 12% of those with type C were in class III or IV or had died at follow-up. The most common causes of death were dysrhythmia, congestive heart failure and sudden and unexplained death.
From 1975 through 1982, the Damus-Stansel-Kaye procedure was performed on 20 patients with complete transposition of the great arteries (TGA) and on 4 with double-outlet right ventricle (DORV) and subpulmonary ventricular septal defect (VSD). The patients ranged from 6 days to 20 years old (median age, 13 months). Associated anomalies included atrial septal defect (24 patients), VSD (14), and others (25). Thirteen patients had had palliative operations previously. Of the 14 hospital deaths (58%), 13 occurred among the 17 patients with one or more risk factors: age less than 18 months, weight less than 10 kg, and left ventricular peak systolic pressure less than 75% of systemic pressure. Follow-up ranged from 12 to 87 months (mean, 51 months). One patient died of cardiac failure two years postoperatively, and 2 required conduit replacement at 40 and 50 months because of stenosis. All 9 survivors are free from major symptoms. The Damus-Stansel-Kaye repair is most suitable for patients with TGA or DORV with subpulmonary VSD who are older than 18 months, weight more than 10 kg, and have a "prepared left ventricle," and whose coronary artery anatomy precludes transplantation.
The cardiorespiratory response to exercise was measured in 27 children with functional single ventricle. All 27 patients had a significant reduction in exercise time, work performed, maximal exercise heart rate, maximal oxygen uptake and systemic arterial blood oxygen saturation. The reduction in exercise performance increased with increasing age of the patients. All patients ventilated excessively at rest and during exercise. This study documented the precise level of exercise intolerance in patients with functional single ventricle. The progressive deterioration in exercise performance with increasing patient age may lend credence to the concept that operation for physiologic correction of functional single ventricle should be considered during or before adolescence.