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Biomedical subjects

R Holt

Publications and source records attributed to R Holt.

At least 37 records · Page 2Linked to original sources
PubMed1997

Towards gene therapy of Hurler syndrome.

Allogeneic bone marrow transplantation is the most effective treatment for Hurler's syndrome. However, due to a lack of matched related donors and unacceptable morbidity of matched unrelated transplants, this therapy is not available to all patients. Therefore we have been developing an alternative approach based on transfer and expression of the normal gene in autologous bone marrow. A retroviral vector carrying the full length cDNA for alpha-L-iduronidase has been constructed and used to transduce bone marrow from patients with this disorder. A number of different gene transfer protocols have been assessed including the effect of intensive schedules of exposure of bone marrow to viral supernatant and the influence of growth factors. With these protocols we have demonstrated successful gene transfer into primitive CD34+ cells and subsequent enzyme expression in their maturing progeny. Also, using long-term bone marrow cultures, we have demonstrated high levels of enzyme expression sustained for several months. The efficiency of gene transfer has been assessed by PCR analysis of haemopoietic colonies as around 50%. No advantage has been demonstrated for the addition of growth factors or intensive viral exposure schedules. Indeed a possible disadvantage has been identified for the use of intensive transduction procedures. The enzyme is secreted into the medium and functional localisation has been demonstrated by reversal of the phenotypic effects of lysosomal storage in macrophages. This pre-clinical work forms the basis for a clinical trial of gene therapy for Hurler syndrome.

Bone Marrow Cells↗
PubMed1997

Serotonin levels as a function of age in Aplysia californica.

The neurotransmitter serotonin (5-HT) plays an important role in a number of behaviors in Aplysia californica some of which have been shown to vary with age. We were thus interested in examining the age-dependence of 5-HT in A. californica. Because animals of the same age can have very different weights, and weight alone is reliably known for wild-caught animals, we also examined the variation of 5-HT with weight. Serotonin was measured in the ring and abdominal ganglia combined, in lab-reared animals from 3 to 12 months post-hatch across a wide weight range. Serotonin increased rapidly from 4 to 6 months, and more slowly from 6 to 13 months. Serotonin scaled by soluble ganglion protein increased from 3 to 6-7 months, reached a maximum, and then decreased again. Serotonin, but not scaled 5-HT, increased significantly with weight across the whole weight range. Animals of the same weight, but different ages, had different 5-HT levels, as did young animals of the same age but different weight. Serotonin varied significantly with both age and weight, with the age-dependence being the more significant.

Aging↗
PubMed1997

Looming vulnerability to spreading contamination in subclinical OCD.

The present study examined the hypothesis, stimulated by the looming vulnerability model of anxiety (Riskind, in press, Behaviour Research and Therapy), that subclinical OCD is associated with a subjective sense of looming vulnerability. One-hundred and four undergraduates rated vignettes of common, everyday situations involving exposure to possible dirt, germs, or contamination. Participants in a subclinical obsessional group had a far higher sense of looming vulnerability to spreading contamination than did those in a control group. Results verified that the subjective sense of looming vulnerability still had separate, distinct and significant contributions to fear-of-contamination symptoms, with the effects of cognitive appraisals of other aspects of threat (such as probability of harm, or lack of control) removed. In contrast, these other cognitive appraisals had no significant associations with symptoms that proved to be independent of the subjective sense of looming vulnerability. A path analysis further explored the dependency of these other cognitive appraisals on looming vulnerability. This analysis found that part of the effects of the subjective sense of looming vulnerability on fears may be indirect and mediated via correlated effects of other cognitive appraisals.

Adult↗
PubMed1996

Inhaled nitric oxide increases coronary artery patency after thrombolysis.

BACKGROUND: Nitric oxide (NO) and nitrosovasodilators that release NO inhibit platelet aggregation. The antithrombotic effect of intravenously infused nitrosovasodilators is usually accompanied by systemic vasodilation. Inhaled NO is a pulmonary vasodilator that does not produce systemic hemodynamic effects. This study examines the antithrombotic effect of inhaled NO in a canine model of platelet-mediated coronary artery reocclusion after thrombolysis. METHODS AND RESULTS: In 25 anesthetized dogs, a segment of the left anterior descending coronary artery was traumatized and a high-grade stenosis created. Thrombus was injected at this site, and tissue plasminogen activator was administered, producing cyclic flow variations (CFVs) in 24 of 25 dogs. CFV frequency was unchanged in dogs not breathing NO but decreased by 35 +/- 9% (P < .05) and 53 +/- 7% (P < .01) while dogs breathed 20 and 80 parts per million (ppm) NO, respectively. The coronary artery patency ratio (fraction of time during which the coronary artery was patent; CAPR) was unchanged in dogs not treated with NO but increased from 51 +/- 7% to 64 +/- 8% while breathing 20 ppm NO (P < .01) and from 49 +/- 3% to 75 +/- 7% while breathing 80 ppm NO (P < .01). The increased CAPR during 80 ppm NO administration persisted during a 45-minute posttreatment period (70 +/- 7%, P < .05 versus baseline). NO inhalation did not change systemic hemodynamics. In a pharmacological model of coronary vasoconstriction, inhaled NO did not reverse the effect of the thromboxane A2 agonist U-46619. In vitro ADP-induced platelet aggregation was inhibited by NO gas. CONCLUSIONS: Inhaled NO at concentrations of 20 and 80 ppm increases coronary patency and decreases CFV frequency in a canine model of platelet-mediated coronary reocclusion after thrombolysis without producing systemic hemodynamic effects.

Adenosine Diphosphate↗
PubMed1996

The effect of domestic water filters on water fluoride content.

The effect of filtration on water fluoride level was investigated in a study using commercially available filters. Testing was carried out in London (low fluoride), Braintree (optimum fluoride, naturally occurring) and Birmingham (optimum fluoride, artificially adjusted). It was found that none of the filters removed fluoride. In Birmingham, but not in either Braintree or London, there was a small, clinically insignificant increase in fluoride levels with filtration using two of the five filters. It is concluded that the water filtration systems tested will not affect the advantage offered by optimum water fluoride levels. Fluoride dietary supplements should not be prescribed for children living in optimal fluoride areas, irrespective of whether they use household filters.

Analysis of Variance↗
PubMed1996

Long-term in vitro correction of alpha-L-iduronidase deficiency (Hurler syndrome) in human bone marrow.

Allogeneic bone marrow transplantation is the most effective treatment for Hurler syndrome but, since this therapy is not available to all patients, we have considered an alternative approach based on transfer and expression of the normal gene in autologous bone marrow. A retroviral vector carrying the full-length cDNA for alpha-L-iduronidase has been constructed and used to transduce bone marrow from patients with this disorder. Various gene-transfer protocols have been assessed including the effect of intensive schedules of exposure of bone marrow to viral supernatant and the influence of growth factors. With these protocols, we have demonstrated successful gene transfer into primitive CD34+ cells and subsequent enzyme expression in their maturing progeny. Also, by using long-term bone marrow cultures, we have demonstrated high levels of enzyme expression sustained for several months. The efficiency of gene transfer has been assessed by PCR analysis of hemopoietic colonies as 25-56%. No advantage has been demonstrated for the addition of growth factors or intensive viral exposure schedules. The enzyme is secreted into the medium and functional localization has been demonstrated by reversal of the phenotypic effects of lysosomal storage in macrophages. This work suggests that retroviral gene transfer into human bone marrow may offer the prospect for gene therapy of Hurler syndrome in young patients without a matched sibling donor.

Antigens, CD34↗
PubMed1995

Costs and management of urinary incontinence in long-term care.

The three aims of the study were (1) to assess the impact and cost of urinary incontinence in long-term care, (2) to determine whether 24-hour incontinence monitoring provides information that improves management, and (3) to ascertain whether costs (nursing time and laundry) could be reduced. The setting was two 24-bed long-term care units in an urban hospital. The research was conducted in three stages. During the initial stage, the impact of incontinence was measured on each unit. Impact was defined as total number of incontinent episodes, nursing time spent changing these patients, and laundry costs, measured during a 7-day period on each unit. After this phase of the investigation, individualized 24-hour incontinence monitoring, followed by recommendations and implementation of care plan, was carried out on one unit. No monitoring or recommendations for care were completed on the other unit, which served as a control. During the third phase of the study, the number of incontinent episodes, nursing time, and laundry costs were again measured on both units. Initially (58%) of residents (24/48) were incontinent, representing 859 episodes of urinary leakage each week that required 45 hours of nursing time to change clothing, containment devices, and bed linens. The direct costs of the nursing time and laundry, expressed in Canadian dollars were $8.60/day per incontinent resident. After 24-hour monitoring of 10 residents one on unit, suggestions were made for various incontinence management programs. An unexpected but simple recommendation was a change to a better containment system for urinary leakage. When impact was measured, a 13% reduction in the number of incontinent episodes was found.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1993

A chimeric murine/human antibody Fab fragment directed against the platelet GPIIb/IIIa receptor enhances and sustains arterial thrombolysis with recombinant tissue-type plasminogen activator in baboons.

Inhibition of the platelet glycoprotein (GP) IIb/IIIa receptor with the murine monoclonal antibody 7E3 abolishes ex vivo platelet aggregation, reduces thrombogenicity, and sustains arterial recanalization with recombinant tissue-type plasminogen activator (rt-PA). A chimeric murine/human Fab fragment of 7E3 (c7E3-Fab) has a markedly reduced immunogenicity, but its potency as an adjunct for thrombolysis with rt-PA has not been evaluated. The effects of a single intravenous bolus injection of aspirin (17 mg/kg) or c7E3-Fab (0.45 mg/kg) on thrombolysis and reocclusion induced with rt-PA were studied in groups of six baboons with femoral arterial thrombosis and superimposed high-grade stenosis. This dose of c7E3-Fab blocked 96 +/- 1% of the platelet GPIIb/IIIa receptors and abolished ADP-induced platelet aggregation. Bolus intravenous injections of rt-PA (0.25 mg/kg) were repeated at 15-minute intervals until reperfusion occurred (maximum of four injections). In the aspirin group, reperfusion was obtained within 51 +/- 16 minutes (mean +/- SD) but was rapidly followed by reocclusion within 6 +/- 9 minutes and by cyclic reflow and reocclusion. In the c7E3-Fab group, reperfusion was obtained within 25 +/- 8 minutes (P < .01 versus aspirin group) and was associated with a delayed reocclusion of 63 +/- 63 minutes (P < .05 versus aspirin group). Template bleeding times remained unchanged in the aspirin/rt-PA group but were markedly prolonged (to > 30 minutes) in the c7E3-Fab/rt-PA group.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Developing leaders from within.

Now more than ever, hospital administrations and staff need to respond quickly and decisively as the rules of the game continue to change, or lose their competitive advantages. With the prospect of massive and radical reform of the health care system over the next 2-3 years, hospital managers and their staffs are going to be asked to integrate and implement more complex changes in shorter and shorter time frames. Externally driven changes in the structure and operation of hospitals will mean changes in individual job profiles, organizational performance measurements, patient care responsibilities, information systems and regulatory requirements, to name but a few.

Hospital Administrators↗
PubMed1992

Epimorphic vs. tissue regeneration in Xenopus forelimbs.

Postmetamorphic froglets of Xenopus laevis regenerate hypomorphic unbranched spikes from amputated arm stumps. These are composed primarily of cartilage, produced from blastemalike structures sparsely populated with cells and rich in connective tissue. Some consider these outgrowths to be an example of epimorphic regeneration produced from blastemas, albeit deficient ones. Others interpret them as a case of tissue regeneration derived from fibroblastemas augmented by chondrocytes and periosteal and perichondrial fibroblasts. To resolve these alternatives, forelimbs were amputated proximal to the wrist, skinned, and inserted through the body wall into the abdominal cavity. In the absence of skin, epidermal wound healing failed to occur and blastemas could not develop. After 2 months, by which time controls had regenerated spikes averaging 3.38 mm long, the denuded stumps had not given rise to outgrowths. They typically developed cartilaginous caps on the severed ends of the radius-ulna, and in rare cases formed amorphous growths of cartilage. If blastema formation is considered diagnostic of epimorphic regeneration and tissue regeneration can proceed in the absence of epidermal wound healing and blastema formation, these findings lead to the conclusion that Xenopus limb regeneration is epimorphic.

Animals↗
PubMed1992

Mycoplasmas in the plaque and saliva of children.

Plaque and saliva samples from 60 children were screened for the presence of mycoplasmas. Each child provided a sample of stimulated saliva and one of plaque from the buccal surface of the most posterior tooth in the upper right quadrant. Mycoplasmas were cultured from 93% of the saliva samples and from 50% of the plaque samples. At the time of sampling, gingivitis was assessed at the site adjacent to that from which the plaque was taken. Mycoplasmas were found significantly more often in plaque from sites in which the adjacent gingivae exhibited inflammation than from sites in which no inflammation was detectable. The proportion of mycoplasmas in plaque from samples adjacent to inflamed gingivae was significantly greater than that in plaque from sites which were clinically healthy. A similar pattern was detected in the corresponding saliva samples. The finding of a greater incidence, together with increased levels, of mycoplasmas in plaque samples from sites with gingivitis may suggest a role for these organisms in this condition.

Child↗
PubMed1990

Lysis of plasminogen activator-resistant platelet-rich coronary artery thrombus with combined bolus injection of recombinant tissue-type plasminogen activator and antiplatelet GPIIb/IIIa antibody.

Resistance of coronary occlusive thrombus to thrombolytic therapy, found in some patients with acute myocardial infarction, may be due to the presence of platelet-rich coronary clot. Reperfusion therapy in such patients may require the development and evaluation of alternative strategies in animal models. Therefore, platelet-rich coronary artery thrombus was developed by excision, eversion (inside out) and reanastomosis of a 1 cm segment of the left circumflex coronary artery in anesthetized dogs maintained on heparin antiocoagulation. Blood flow was restored in 25 of 27 dogs. Thrombotic occlusion of the everted segment graft with primarily platelet-rich thrombus or thrombus containing platelet-rich and erythrocyte-rich zones, persisting for at least 30 min, occurred within 4.5 +/- 3.5 min (mean +/- SD) in 20 of these 25 dogs. In 5 of these 20 dogs (group I, control), stable occlusion, as monitored with an ultrasound flow probe and coronary angiography, was maintained during a 2 h observation period. In group II (n = 5), intravenous bolus injections of recombinant tissue-type plasminogen activator (rt-PA) at a dose of 0.45 mg/kg body weight at four 15 min intervals did not cause reperfusion in four dogs and produced cyclic reperfusion and reocclusion in one dog. In group III (n = 5), a single intravenous bolus injection of 0.8 mg/kg of the F(ab')2 fragment of a murine monoclonal antibody (7E3) against the human platelet GPIIb/IIIa receptor [7E3-F(ab')2] produced stable reperfusion in two of the five dogs, whereas occlusion persisted in the other three. In group IV (n = 5), injection of 7E3-F(ab')2 (0.8 mg/kg) followed by rt-PA (0.45 mg/kg) caused stable reperfusion without reocclusion in all dogs (p less than 0.05 versus rt-PA alone and p less than 0.01 versus control). This study confirms that platelet-rich occlusive coronary thrombus is very resistant to lysis with intravenous rt-PA. However, this resistance may be overcome by the combined use of a reduced dose of rt-PA and the antiplatelet GPIIb/IIIa receptor antibody 7E3. The results indicate that platelet-rich thrombus resistant to thrombolytic agents may be dispersed pharmacologically without resort to mechanical recanalization. The present dog model may be useful in investigating specific strategies for the dispersion of resistant platelet-rich coronary thrombus.

Animals↗
PubMed1990

Comparative effects of aspirin, a synthetic thrombin inhibitor and a monoclonal antiplatelet glycoprotein IIb/IIIa antibody on coronary artery reperfusion, reocclusion and bleeding with recombinant tissue-type plasminogen activator in a canine preparation.

The comparative effects of intravenous aspirin, the synthetic thrombin inhibitor (2R,4R)-4-methyl-1-[N2-(3-methyl-1,2,3,4-tetrahydro-8- quinolinesulfonyl)-L-arginyl]-2-piperidinecarboxylic acid monohydrate (Argatroban) and F(ab')2 fragments of monoclonal antibody 7E3 against platelet glycoprotein IIb/IIIa (7E3-F[ab']2) on thrombolysis, reocclusion and bleeding associated with 0.45 mg/kg body weight bolus injections of recombinant tissue-type plasminogen activator (rt-PA) were studied in a canine coronary artery thrombosis model. Coronary patency was monitored for 2 h both by flow probe and by coronary angiography. Four groups were studied: Group I = pretreated with 17 mg/kg intravenous aspirin (n = 6), Group II = pretreated with 200 micrograms/kg per min intravenous Argatroban for 60 min (n = 5), Group III = pretreated with aspirin and Argatroban (n = 5) and Group IV = pretreated with 0.8 mg/kg intravenous 7E3-F(ab')2 (n = 5). In Group I, reflow occurred in four of six dogs, but did not persist; reflow was induced in Group II in four of five dogs, persisting in one; in Group III, reflow occurred in all five dogs, persisting in four; in Group IV reflow was achieved in four of five dogs, persisting in two. The frequency of persistent reflow in Group III was significantly higher than in the combined Groups I and II (p = 0.012), whereas the time to reflow was significantly shorter in the groups receiving Argatroban than in the aspirin group (median 25 versus 55 min, p = 0.04). There were no significant differences between Groups III and IV.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Pharmacodynamic study of F(ab')2 fragments of murine monoclonal antibody 7E3 directed against human platelet glycoprotein IIb/IIIa in patients with unstable angina pectoris.

The pharmacodynamics of intravenous bolus injections of 0.05, 0.10, 0.15, and 0.20 mg/kg of F(ab')2 fragments of the murine monoclonal antibody 7E3, 7E3-F(ab')2, directed against the glycoprotein IIb/IIIa (GPIIb/IIIa) receptor of human platelets, were studied in groups of four patients with unstable angina pectoris. With 0.20 mg/kg, the template bleeding time prolonged from 6.3 +/- 1.9 (mean +/- SD) to greater than 30 min; it subsequently decreased to 13 +/- 7.8 min after 12 h and to 8.3 +/- 1.5 min after 24 h. The number of unblocked GPIIb/IIIa receptors (preinfusion value, 32,000 +/- 3,000 per platelet) decreased to 13 +/- 7% of the preinfusion value 1 h after infusion, and then increased to 33 +/- 10% at 12 h, 44 +/- 8% at 24 h and 67 +/- 7% at 72 h. The logarithm of the bleeding time was inversely proportional with the residual GPIIb/IIIa receptors (r = 0.73, P less than 0.0001). ADP-induced platelet aggregation (measured by changes in light transmittance in percent) decreased from 60 +/- 5% before infusion to 1.5 +/- 3% 1 h after infusion; it then increased to 29 +/- 3% after 24 h and 39 +/- 6% after 72 h. Platelet counts decreased by 16% at 1 h and returned to control values within 24 h. Proportionally smaller effects were seen at lower doses of 7E3-F(ab')2. Antibody injection did not induce spontaneous bleeding. Angina was not observed during the first 12 h when the bleeding time was significantly prolonged, but occurred in 6 of the 16 patients within the next 3 d. 2 of the 16 patients developed low titers of IgG antibodies specific for 7E3-F(ab')2. Thus 7E3-F(ab')2 induces dose-related inhibition of platelet function; at a dose of 0.20 mg/kg, it causes profound inhibition of platelet aggregation and prolongation of the bleeding time, but no spontaneous bleeding.

Adult↗
PubMed1990

Characterization of the subgingival microbial flora around endosteal sapphire dental implants in partially edentulous patients.

The microbiota associated with oral endosteal sapphire ceramic implants was studied using cultural methods. Samples were taken from both implant and control (tooth) sites, and comparisons were made between healthy and diseased and between implant and control sites. Diseased sites harbored a microbiota with a large number and proportion of Gram-negative anaerobic rods, black-pigmented Bacteroides, and surface translocating bacteria. Healthy sites in the same patients had smaller amounts of bacteria dominated by facultative Gram-positive cocci and rods. The microbiota in diseased and healthy implant and control sites was very similar. It is suggested that peri-implant tissues behave very similarly to periodontal tissues and that peri-implantitis lesions should be considered as site-specific infections harboring a high number of periodontal pathogens, mainly Gram-negative anaerobic rods.

Aluminum Oxide↗