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Biomedical subjects

R L Harrison

Publications and source records attributed to R L Harrison.

17 recordsLinked to original sources
PubMed1992

Concurrent protein C deficiency and lupus anticoagulants.

An inherited deficiency of protein C, a recognized hypercoagulable state, may cause a clinically significant deep venous thrombosis. Only some persons with a deficiency of protein C experience thrombosis, and almost always the thrombotic event occurs in the venous circulation. Warfarin-induced skin necrosis, a rare event observed in some patients soon after treatment with warfarin is begun, is believed to be another manifestation of this deficiency. We describe a young woman whose basal functional and antigenic levels of protein C were about 45% and who experienced both deep venous thrombosis and warfarin-induced skin necrosis in a clinically severe course. Evidence for lupus anticoagulants was present, with prolonged activated partial thromboplastin time that was corrected when lysed platelets were added, prolonged Russell's viper venom time, anticardiolipin antibodies, and other laboratory evidence. Lupus anticoagulants are associated also with a significant incidence of thrombosis, including arterial thrombosis, and this patient developed concurrently arterial thrombosis. The combined effects of protein C deficiency and lupus anticoagulants, exacerbated by other potentially thrombogenic conditions, are believed responsible for the severe thrombotic events experienced by this patient.

Autoantibodies↗
PubMed1990

A comparison between hemogram data as measured by technical and non-technical personnel using the QBC II.

Diagnostic testing is becoming relatively common practice in small laboratories associated with physicians' offices. Often the test that can be performed in this setting are limited to those that use relatively inexpensive equipment that can be operated by personnel who are not trained laboratorians. The QBC II is an instrument that has been promoted as a semiautomated instrument that is particularly appropriate in this setting. This study addressed the question of comparability of data produced by technical and non-technical operators.

Hematocrit↗
PubMed1990

Detached ciliary tufts. Comparison with intestinal protozoa and a review of the literature.

Detached ciliary tufts are structures of doubtful pathologic significance that are normally present in many body fluids. However, their existence is not widely appreciated by pathologists practicing routine laboratory medicine. If they are observed, their practical clinicopathologic importance is that, because of their vigorous ciliary motion in wet mounts, they can imitate ciliated protozoa and pose a diagnostic dilemma. The authors present a brief review of the literature on detached ciliary tufts and a morphologic comparison with the more commonly encountered intestinal protozoa.

Adolescent↗
PubMed1990

The effect of an arenavirus infection on liver morphology and function.

Patients with severe Lassa fever have high serum levels of liver enzymes. Studies of the histology of the liver have shown only minor alterations, seemingly insufficient to account for death. Pichinde virus is an arenavirus which causes severe illness similar to Lassa fever in strain 13 guinea pigs, but does not cause severe illness in man. This can serve as a relatively safe model for studying the pathology and pathophysiology of fatal arenaviral infection. We used this infection to evaluate the effect of arenavirus on liver morphology and function. When guinea pigs were infected with Pichinde virus, all developed severe disease and died within 14 days of infection. The animals lost large amounts of weight. Higher levels of virus were detected in the liver than in serum. Aspartate aminotransferase and alanine aminotransferase were elevated late in the course of the disease; no elevations were seen in gamma glutamyl transpeptidase or bilirubin. Alkaline phosphatase, initially high in these growing animals, was markedly decreased early in infection. Prothrombin time and activated partial thromboplastin time were increased late in the disease, and decreased levels of Factors VIII and IX were seen relatively early. Fatty metamorphosis, indicating problems in lipid processing, occurred by day 11, but necrosis was minor and occurred late. Pichinde virus infection results in significant alterations in the metabolic and synthetic capacities of the hepatocytes early in infection in the absence of significant necrosis.

Alanine Transaminase↗
PubMed1989

Human hepatic sinusoidal endothelial cells in culture produce von Willebrand factor and contain Weibel-Palade bodies.

Human hepatic sinusoidal endothelial cells were derived from cadaveric human livers. Cells were grown in culture for several weeks to produce small patches of confluent endothelial cells. The ultrastructure of sinusoidal endothelial cells was examined, cell monolayers were stained immunocytochemically for von Willebrand factor antigen, and antigen in cell culture media was measured by enzyme-linked immunosorbent assay. Human hepatic sinusoidal endothelial cells contained von Willebrand factor antigen and Weibel-Palade bodies, were fenestrated, and released von Willebrand factor antigen into media in a time-dependent manner. Although in some respects human hepatic endothelial cells were different from vascular cells, there was no evidence that there were qualitative differences in their capacity to produce von Willebrand factor.

Cells, Cultured↗
PubMed1989

Challenges and dilemmas in behaviour guidance of the pediatric dental patient.

In addition to the pressures of providing a high quality of dental care for children, dentists practising pediatric dentistry are faced with some legal and ethical concerns regarding the use of behaviour management techniques. The following article will discuss some of the pressures and ethical dilemmas facing dentists treating children. Strategies for making the dental appointment more humane for child, parent and dentist are suggested. The most perplexing issues in pediatric dentistry today are related to the management of patients. In addition to questions regarding clinical management, dentists treating children have to make careful judgements concerning management of patient's behaviour. The following scenarios are a few examples of the situations that often arise during the dental treatment of child and adolescent patients: "I really had to raise my voice to Jamie today and use a lot of physical restraint to administer the local anesthetic. I was not happy about being so aggressive, but it was important to get that filling done. I wonder, though, how he is going to feel about going to the dentist now?" "I feel frustrated that I did not get any work done on that four-year-old today, but I did not want to use undue force. Maybe I should have been more forceful; hand-over-mouth-exercise might have worked, but I always feel uncertain about using that technique and I wonder what the parents will think if I use it."

Adolescent↗
PubMed1989

Resin-bonded bridges for the pediatric patient.

The resin-bonded bridge is a relatively new clinical technique that has had favorable clinical reports. Recently, new materials and techniques have been developed which may improve the retention of resin-bonded bridges. This article reviews recent developments concerning resin-bonded bridges, present a case report, and give practical suggestions regarding the fabrication of resin-bonded bridges.

Adolescent↗
PubMed1988

The thrombin clotting time. Evaluation of Thromboquik, a commercial thrombin reagent, and observations on sensitivity and on centrifugation.

The thrombin clotting time (TCT) is an important screening test of coagulation, but thrombin can be a troublesome reagent to use, and in general the TCT has not been well standardized, even with respect to the ideal normal range. Thromboquik is a thrombin reagent that is convenient in its day-to-day use and that exhibits prolonged stability after reconstitution. As an extension of an evaluation of this commercial thrombin reagent, the authors have made several observations about the TCT itself. In a comparison between multiple pairs of TCT reagents, the relative extent of departure of clotting times from normal, for any given abnormal plasma sample, was not predictably related to the mean normal clotting times of the two reagents. The authors also concluded that centrifugation of blood at 1,500 X g is inadequate to prepare plasma for the TCT.

Blood Coagulation Tests↗
PubMed1987

Concurrent lupus anticoagulants and prothrombin deficiency due to phenytoin use.

A man with lupus anticoagulant and a prothrombin deficiency was studied before and after cessation of treatment with phenytoin. Multiple abnormal laboratory values of the following partially or completely resolved after the patient's therapy was discontinued: tissue thromboplastin inhibition ratio, prothrombin time, activated partial thromboplastin time, anticardiolipin antibodies, and quantitative measures and abnormal pattern on crossed immunoelectrophoresis of prothrombin. This patient represented an example of a concurrent drug-induced prothrombin deficiency and a lupus anticoagulant.

Adult↗
PubMed1979

Direct effects of trypan blue on thyroid secretion.

Trypan blue directly inhibited in vitro thyroid secretion (butanol soluble 125I release to the media) induced by both thyroid stimulating hormone (TSH) and dibutyryl cAMP. Intracellular colloid droplet counts were also decreased. Inhibition was directly proportional to dye concentration and could be overcome by supramaximal TSH and dibutyryl cAMP. Inhibition could be observed as early as 20 min of incubation, was not increased by preincubation, and could even be demonstrated after TSH in vivo. Trypan blue, in vivo, produced similar inhibition of thyroid secretion. Incubation of 125I-thyroglobulin with lysosomal enzymes revealed inhibition with much lower concentrations of dye. Inhibition of lysosomal enzyme(s) would not appear to explain the marked decreases in colloid droplets, and this may represent two separate effects of trypan blue on thyroid secretion.

Animals↗
PubMed1979

Creatine kinase isoenzymes of mitochondrial origin in human serum.

We measured creatine kinase (EC 2.7.3.2) activity in 1009 serum samples from 538 patients in the intensive-care units of the University of Texas Medical Branch hospitals. Creatine kinase isoenzymes migrating cathodal to skeletal muscle creatine kinase (CK-MM) on cellulose acetate electrophoresis were found in sera from 14 of the 538 patients. Creatine kinase, lactate dehydrogenase (EC 1.1.1.27), aspartate aminotransferase (EC 2.6.1.1), and alanine aminotransferase (EC 2.6.1.2) activities were abnormally increased in these 14 patients. Liver lactate dehydrogenase isoenzyme (LDH5) and cardiac creatine kinase isoenzyme (CK-MB) were abnormally increased in 12 and eight of these patients, respectively. Ten of the 14 patients died during their hospital admission. We believe the creatine kinase isoenzymes that migrated cathodal to skeletal muscle creatine kinase (CK-MM) were of mitochondrial origin.

Adolescent↗
PubMedDate not supplied

The use of importance sampling techniques to improve the efficiency of photon tracking in emission tomography simulations.

Monte Carlo simulations are widely used to study the transmission and scattering of gamma rays. Use of this method for simulations of emission tomographs suffers from geometric inefficiency resulting from the low solid angle of acceptance of most tomograph designs. We have applied several importance sampling techniques--stratification, forced detection, and weight control through Russian roulette and splitting--to increase the computational efficiency of the Monte Carlo method 10- to 300-fold. A description of these techniques, their validation, and sample performance results are given. Application of importance sampling methods makes it practical to study photon scattering in heterogeneous attenuators on workstations and minicomputers.

Electrons↗
PubMedDate not supplied

The association of simple anterior dental crossbite to gingival margin discrepancy.

The purpose of this study was to determine the severity of gingival margin discrepancy affecting the mandibular incisors in children with a single-tooth anterior crossbite. The response of the position of the gingival margin to correction of the crossbite also was investigated. Twenty-two subjects with a single central crossbite and 16 subjects with a single lateral crossbite were identified from two orthodontic practices. Seventeen of the 22 central incisor patients had immediate posttreatment records available; six patients had long-term follow-up records. An insufficient number of posttreatment records were available for the patients with lateral crossbites. The mean clinical crown length of crossbite mandibular incisors, measured on the study models, was compared with mean crown length of contralateral control incisors and the difference in clinical crown length was determined. A gingival margin discrepancy was identified when the gingival margin of the crossbite incisor was at least 1.0 mm apical to the gingival margin of the control incisor. The proportion of subjects with gingival margin discrepancy was significantly higher in subjects with central incisor crossbite (12/22 = 54%) than in those with lateral incisor crossbite (4/16 = 25%), P less than 0.05. While a gingival margin discrepancy persisted for eight of the 17 central incisor crossbites after discontinuing the appliance, 8.9 +/- 4.7 months, the severity of the discrepancy showed a significant reduction from 2.2 +/- 0.5 mm to 1.3 +/- 0.8 mm, P less than 0.05. True recession with exposure of cementum was not observed in any subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Child↗
PubMedDate not supplied

A study of aspirin induced changes in bleeding time, platelet aggregation, and Sonoclot coagulation analysis in humans.

The purpose of this study was to determine whether or not a newer test of platelet function, Sonoclot coagulation analysis, can identify the patients who develop significant prolongation of bleeding time after aspirin ingestion. Template bleeding time, platelet aggregation in response to arachidonic acid, collagen, epinephrine, adenosine diphosphate, and ristocetin, and Sonoclot coagulation analysis were performed before and after ingestion of aspirin in 22 adult volunteers. Mean bleeding time increased from 5.32 +/- 2.16 min to 7.34 +/- 2.1 min, but remained within normal range (2.5 to 9 min). There was marked intersubject variability in the effect of aspirin on bleeding time, and difference between men and women was not significant. There was significant decrease in platelet aggregation in response to arachidonic acid, collagen and epinephrine. Sonoclot coagulation analysis did not show significant effect of aspirin administration. There was no correlation among changes in bleeding time, platelet aggregation, and Sonoclot coagulation analysis. Five patients with known platelet function disorders and prolonged bleeding times (mean = 18.5 min, range 14 to 22) without any other coagulation abnormalities were also studied. In four of these patients who had normal platelet count, Sonoclot graphs were morphologically similar to those in the volunteers with normal bleeding times, but in one patient with thrombocytopenia, morphology was altered. It is our conclusion that Sonoclot coagulation analysis is unlikely to identify patients with prolonged bleeding time in whom platelet count and other coagulation factors are normal.

Adult↗