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Biomedical subjects

R L Harrison

Publications and source records attributed to R L Harrison.

At least 19 recordsLinked to original sources
PubMed1995

Fleas on gray foxes in New Mexico.

From April 1992 to April 1993, fleas were collected from 15 gray foxes, Urocyon cinereoargenteus Schreber, in New Mexico. Flea species collected were Cediopsylla inaequalis inaequalis Baker (14/15), Echidnophaga gallinacea (Westwood) (1/15), Euhoplopsyllus glacialis affinis Baker (10/15), Foxella ignota Baker (1/15), Pulex irritans (L.) (6/15), and Pulex simulans Baker (15/15). C. i. inaequalis and F. ignota are new host records for gray foxes. The collection of C. i. inaequalis, E. g. affinis, F. ignota, and P. simulans are new host records for New Mexico. Fleas on gray foxes in the Southwest are reviewed.

Animals↗
PubMed1995

Mutations in the Autographa californica multinucleocapsid nuclear polyhedrosis virus 25 kDa protein gene result in reduced virion occlusion, altered intranuclear envelopment and enhanced virus production.

Serial passage of nuclear polyhedrosis viruses (NPVs) through cultured cell lines results in the appearance of mutants with a complex phenotype referred to as the 'few polyhedra' (FP) phenotype. The altered plaque morphology and reduced occlusion production associated with the FP phenotype have been observed in Autographa californica multinucleocapsid nuclear polyhedrosis virus (AcMNPV) bearing mutations in the gene encoding the 25 kDa protein (25K gene). In this study, we sequenced the 25K genes of four spontaneously occurring AcMNPV FP mutants. These mutants, together with an artificially generated FP mutant (AcFP beta gal, in which the gene for beta-galactosidase is fused in frame with the 25K ORF), were examined at the ultrastructural level to see if they exhibited the reduced virion occlusion and intranuclear envelopment which is associated with the FP phenotype. Observations on Spodoptera frugiperda Sf9 cells infected with the FP mutants revealed that all five mutants were impaired in virion occlusion and intranuclear nucleocapsid envelopment. The 25K mutants were also found to release two- to fivefold more infectious virus (p.f.u.) into the media of infected Sf9 cells. Marker rescue of AcFP beta gal restored wild-type virion occlusion, intranuclear envelopment and levels of infectious virus production.

Alleles↗
PubMed1993

Caries experience of Native children of British Columbia, Canada, 1980-1988.

Surveys of the dental health of Native children in British Columbia, Canada, were conducted in 1980, 1984 and 1988 by Medical Services Branch, Health and Welfare Canada. Data were gathered on children turning 5, 7, 9, 11, 13, and 15 yr of age in each survey year. This paper analyzes the findings related to dental caries and the treatment of caries. Comparisons were made between the 1980 and 1988 surveys using Student's t-tests; data from the 1984 survey were included for comparison. Results of these surveys demonstrate a continuous improvement in the dental health of Native children between the years 1980 and 1988, but the improvement was limited to the permanent dentition. The deft for 5-yr-olds remained constant over the time interval. In contrast, the DMFT for each group significantly decreased from 1980 to 1988 (P < 0.05). The percentage of 5-yr-old children who were caries-free in the primary dentition remained constant, and primary tooth mortality (tooth abscessed or with crown destroyed) in 5-yr-olds did not change. However, the percentage of children surveyed with caries-free permanent teeth improved significantly at each survey year and permanent tooth mortality significantly declined (P < 0.05). The proportion of filled, compared with carious, primary and permanent teeth increased from 1980 to 1988. In contrast, the number of extracted primary teeth stayed relatively constant for 5-yr-olds, but the proportion of missing teeth declined significantly for all other age groups (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
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↗
PubMed1984

Estrogen stimulates von Willebrand factor production by cultured endothelial cells.

Monolayers of cultured human umbilical vein endothelial cells were exposed to 17 beta-estradiol and compared to control cultures with respect to levels of von Willebrand factor (vWF) released into the media after 3-5 days of incubation. The amount of functional vWF activity was assessed by ristocetin-induced platelet aggregation and by a radioreceptor platelet assay. vWF antigen was quantitated by immunoassay. The DNA content of each monolayer was determined fluorometrically and used as a measure of cell number. By all assays, vWF levels in the media from the estradiol-treated endothelial cells were reproducibly and significantly higher when compared with control values. The amount of vWF produced by the cultured endothelial cells showed a dose-response effect to the estradiol added to the media. The estradiol-treated cells produced approximately 1.3 +/- 0.30 micrograms vWF/ml/micrograms DNA at 2 ng estradiol/ml, compared with control cultures that produced 0.75 +/- 0.16 microgram vWF/ml/micrograms DNA (p less than 0.001). The estradiol-treated monolayers consistently contained slightly greater amounts of DNA than control cultures: 2.0 +/- 0.10 micrograms versus 1.7 +/- 0.12 micrograms DNA (p less than 0.001). By multivariant analysis, however, the differences in cell number could only account for less than or equal to 10% of the elevation in the level of vWF that occurred in response to estradiol. By SDS-agarose electrophoresis and radioimmunoblotting, the vWF within the cytosol of the endothelial cells was found to possess a multimeric pattern similar to that found for either purified plasma vWF or vWF released into media overlying endothelial cell cultures. Our studies indicate that estrogen directly stimulates endothelial cells to increase their rate of production of vWF and, in addition, causes a slight increase in endothelial cell replication. These data may bear on the observation that administration of estrogen to some women with von Willebrand's disease causes an increase in their functional levels of vWF.

Blood Coagulation Factors↗
PubMed1983

Comparison of thrombin and ristocetin in the interaction between von Willebrand factor and platelets.

It is known that the antibiotic ristocetin exposes the platelet membrane receptor for factor VIII/von Willebrand glycoprotein (FVIII/vWF). Recent reports suggest that low concentrations of thrombin also cause platelet membrane receptors to become available for FVIII/vWF. As a consequence, the suspicion has been raised that thrombin provides similar or equivalent activity in vivo to that observed for ristocetin under in vitro conditions. In this study, we quantitated the extent to which thrombin promotes the binding of FVII/vWF to platelets and determined whether or not this interaction initiates or complements platelet aggregation. With ristocetin present, the amount of 125I-FVIII/vWF that became platelet-bound correlated closely with the onset, rate, and extent of platelet aggregation. In contrast, at every thrombin concentration tested, the amount of 125I-FVIII/vWF that specifically bound to platelets was about 6% of that observed with ristocetin. Significantly, FVIII/vWF did not augment the rate of aggregation of platelets in response to thrombin or initiate platelet aggregation when subaggregating doses of thrombin were used. These observations indicate that the minimal association that occurs between FVIII/vWF and the platelet membrane in the presence of thrombin does not correlate with platelet aggregation and therefore is not analogous to the effects of ristocetin. Whether the low level of binding relates to another process, such as platelet-endothelial interactions, remains unknown.

Blood Platelets↗
PubMed1982

Electron microscopy of human factor VIII/Von Willebrand glycoprotein: effect of reducing reagents on structure and function.

The structure of native and progressively reduced human factor VIII/von Willebrand factor (FVIII/vWF) was examined by electron microscopy and SDS gel electrophoresis and then correlated with its biological activities. Highly resolved electron micrographs of well-spaced, rotary-shadowed FVIII/vWF molecules showed their structure to consist of a very flexible filament that contains irregularly spaced small nodules. Filaments ranged from 50 to 1,150 nm with a mean length of 478 nm and lacked fixed, large globular domains as seen in fibrinogen and IgM. A population of multimeric FVIII/vWF species ranging in molecular weight from 1 to 5 million daltons and differing in size alternately by one and two subunits was observed on SDS-2% polyacrylamide-0.5% agarose gel electrophoresis. With progressive reduction of disulfide bonds by dithiothreitol (DTT), the electron microscopic size of FVIII/vWF decreased in parallel with increased electrophoretic mobility on SDS-agarose gels; between 0.1 and 0.5 mM DTT its structure changed from predominantly fibrillar species to large nodular forms. A 50% loss of vWF specific activity and FVIII procoagulant activity occurred at 0.4 mM DTT and 1 mM DTT, respectively, corresponding to the reduction of 4 and 12 disulfide bonds of the 62 disulfides per 200,000-dalton subunit. We conclude that reduction of a few critical disulfide bonds results in a major structural change by electron microscopy and a concomitant loss of approximately 50% of the vWF function.

Alkylation↗
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↗