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Biomedical subjects

G Pearson

Publications and source records attributed to G Pearson.

At least 55 records · Page 3Linked to original sources
PubMed1997

An in vitro microleakage study of the 'bonded-base' restorative technique.

Microleakage associated with a silver-reinforced restorative glass-ionomer cement (Hi-Dense) used with a composite resin (Z100) in a modified Class II bonded-base technique restoration was evaluated. The influence of long-term artificial saliva storage, thermal and load cycling was also determined. Class II composite (Z100) restorations used with a new dental adhesive system (Scotchbond Multi-Purpose Dental Adhesive) were used as controls. Results showed that the bonded-base technique can reduce the leakage observed with the direct composite technique. Thermocycling decreased the leakage at the composite-enamel interface but had no effect on the leakage at the composite-dentine interface or on the leakage patterns of bonded-base restorations. Load cycling had no significant influence on leakage patterns of either type of restorative mode. Storage in artificial saliva resulted in decreased leakage at the composite-enamel interface but had a minor adverse effect at the glass-ionomer-dentine interface.

Adhesives↗
PubMed1996

Successful external fertilization in turbulent environments.

Mathematical and experimental simulations predict that external fertilization is unsuccessful in habitats characterized by high water motion. A key assumption of such predictions is that gametes are released in hydrodynamic regimes that quickly dilute gametes. We used fucoid seaweeds to examine whether marine organisms in intertidal and subtidal habitats might achieve high levels of fertilization by restricting their release of gametes to calm intervals. Fucus vesiculosus L. (Baltic Sea) released high numbers of gametes only when maximal water velocities were below ca. 0.2 m/s immediately prior to natural periods of release, which occur in early evening in association with lunar cues. Natural fertilization success measured at two sites was always close to 100%. Laboratory experiments confirmed that (i) high water motion inhibits gamete release by F. vesiculosus and by the intertidal fucoids Fucus distichus L. (Maine) and Pelvetia fastigiata (J. Ag.) DeToni (California), and (ii) showed that photosynthesis is required for high gamete release. These data suggest that chemical changes in the boundary layer surrounding adults during photosynthesis and/or mechanosensitive channels may modulate gamete release in response to changing hydrodynamic conditions. Therefore, sensitivity to environmental factors can lead to successful external fertilization, even for species living in turbulent habitats.

Journal Article↗
PubMed1996

The effects of paroxetine and nefazodone on sleep: a placebo controlled trial.

We studied the effect of acute (1 day) and subacute (16 days) administration of the new antidepressant, nefazodone (400 mg daily), and the selective serotonin re-uptake inhibitor (SSRI), paroxetine (30 mg daily), on the sleep polysomnogram of 37 healthy volunteers using a random allocation, double-blind, placebo-controlled design. Compared to placebo, paroxetine lowered rapid eye movement (REM) sleep and increased REM latency. In addition, paroxetine increased awakenings and reduced Actual Sleep Time and Sleep Efficiency. In contrast, nefazodone did not alter REM sleep and had little effect on measures of sleep continuity. We conclude that in contrast to typical SSRIs, nefazodone administration has little effect on sleep architecture in healthy volunteers.

Adolescent↗
PubMed1996

Lessons from a pilot study of transfer factor in chronic fatigue syndrome.

Transfer Factor (TF) was used in a placebo controlled pilot study of 20 patients with chronic fatigue syndrome (CFS). Efficacy of the treatment was evaluated by clinical monitoring and testing for antibodies to Epstein-Barr virus (EBV) and human herpes virus-6 (HHV-6). Of the 20 patients in the placebo-controlled trial, improvement was observed in 12 patients, generally within 3-6 weeks of beginning treatment. Herpes virus serology seldom correlated with clinical response. This study provided experience with oral TF, useful in designing a larger placebo-controlled clinical trial.

Adolescent↗
PubMed1996

Morphological and ultrastructural changes induced in corneal epithelial cells by HIV-1 and HHV-6 in vitro.

PURPOSE: The purpose of this study was to determine whether HIV-1 and HHV-6 are capable of infecting and inducing morphological and ultrastructural changes in corneal epithelial cells in vitro. METHODS: Primary and transformed corneal epithelial cell cultures were infected with HIV-1 or HHV-6 in vitro and analyzed for the presence or absence of viral antigens, DNA sequences, viral particles and inclusions. RESULTS: HIV-1 antigens were detected in 8% of the HIV-1 infected cells and early HHV-6 antigens were present in 12% of the HHV-6 infected cells. The presence of viral DNA sequences in the cultures confirmed these findings. Cells infected with HIV-1 morphologically were not different from uninfected cells, whereas the morphology of HHV-6 infected cells was very similar to cells infected with other human herpesviruses. Cytoplasmic tubuloreticular inclusions were detectable in corneal epithelia cells infected with HIV-1 and intact viral particles were visible only in PBMC used to recover HIV-1 from these cultures. Viral inclusions were also observed in corneal epithelial cells infected with HHV-6. CONCLUSION: These data indicate that HIV-1 and HHV-6 are capable of infecting corneal epithelial cells in vitro, but the viruses are not entering these cells via CD4 or galC receptors. This basic information is important in determining the pathogenic mechanism(s) involved in the development of AIDS-associated corneal disorders.

Antigens, Viral↗
PubMed1995

HIV-1 and HHV-6 antigens and transcripts in retinas of patients with AIDS in the absence of human cytomegalovirus.

PURPOSE: The purpose of this study was to define the agents involved in the development of acquired immune deficiency syndrome (AIDS)-associated retinitis. To achieve this goal, the authors determined the frequency and proximity of the simultaneous presence of human immunodeficiency virus (HIV)-1, human herpesvirus (HHV)-6, and human cytomegalovirus (HCMV) in retinas of patients with AIDS with and without AIDS-associated retinitis. METHODS: Retinal sections from 50 globes from patients with AIDS were analyzed for the presence of viral antigens and transcripts. Group 1 contained 13 globes from patients with HCMV infection. Group 2 contained 20 globes from patients with retinal lesions of uncertain etiology in which HCMV antigen and transcripts were not detected. Group 3 contained 17 globes from patients with no retinal lesions. RESULTS: Retinal sections from all 13 globes (group 1) were positive for HCMV antigens and HIV-1 antigens and transcripts. Six of the 13 retinas were also positive for HHV-6 antigens and transcripts. Sections from 13 of the 20 globes (group 2) were positive for HIV-1 antigens and transcripts, and 5 of these 13 were also positive for HHV-6 antigens and transcripts. Multiple areas in sections from two of the HIV-1-positive retinas showed coinfection with HHV-6. All 17 globes (group 3) were positive for HIV-1 antigens and transcripts. Ten of these 17 retinas were also positive for HHV-6 antigens. Human cytomegalovirus antigens were not detectable in retinas from groups 2 and 3. No viral antigens or transcripts were detectable in retinal sections from 10 HIV-1 negative donors. CONCLUSION: The coexistence of HIV-1 and HHV-6 activity in more than 50% of retinas without HCMV infection suggests that HIV-1 and HHV-6 alone or in combination may predispose retinal tissue to other opportunistic agents such as HCMV during the development of AIDS-associated retinitis.

AIDS-Related Opportunistic Infections↗
PubMed1994

Transmission of bovine spongiform encephalopathy and scrapie to mice: strain variation and the species barrier.

Transmissions of bovine spongiform encephalopathy (BSE) from seven unrelated cattle sources have given remarkably uniform disease characteristics in mice, differing from over twenty previous and contemporary transmissions of sheep and goat scrapie. Transmissions to mice of spongiform encephalopathy from six species (including sheep and goats) which have been experimentally or naturally infected with BSE have given similar results to direct BSE transmissions from cattle. Therefore the BSE agent has retained its identity when passaged through a range of species and the 'donor' species has little specific influence on disease characteristics in mice, adding to evidence for an agent-specific informational molecule. On transmission of BSE or scrapie to mice the incubation periods are long compared with subsequent mouse-to-mouse passages (the 'species barrier'). Contributing factors include a low efficiency of infection on interspecies transmission, the apparent failure of intracerebrally injected 'foreign' inoculum to establish infection directly in mouse brain and the selection of variant strains of agent which replicate most readily in the new host species.

Animals↗
PubMed1994

Surface treatment of alloys for resin adhesion: an in-vitro study.

Successful adhesive dentistry is reliant on the strength and durability of the resin-bond. This is affected by the alloy and its preparation, the properties of the luting resin, and the condition of the tooth. This in-vitro study investigated three months of preparation of the alloy surfaces and three different types of one resin luting cement. Results demonstrated that alumina-blasted nickel-chromium alloy specimens were significantly more resistant to failure under tensile loading than gold alloy samples however prepared. Alumina-blasted, heat-treated gold alloy specimens showed significantly higher tensile failure loads than those of alumina-blasted gold. The performance of the different resins with the alumina-blasted nickel-chromium or the alumina-blasted, heat-treated gold alloy specimens was similar. However, for the alumina-blasted gold alloy specimens, there was a significant difference when comparing resin types.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1993

Identification of a DNA-binding protein of human herpesvirus 6, a putative DNA polymerase stimulatory factor.

A 41K early nuclear antigen (p41), expressed in human herpesvirus type 6 (HHV-6)-infected T cells, was cloned by screening a cDNA expression library with the anti-p41 monoclonal antibody (MAb) C5. When expressed in mammalian cells, the cloned p41 protein comigrated with the authentic p41 protein from HHV-6-infected cells and localized to the nucleus. HHV-6 p41 shares 44% sequence identity with the human cytomegalovirus (HCMV) DNA-binding protein, ICP36 (UL44 gene product); p41 binds to ssDNA with the same apparent affinity as ICP36. Since ICP36 has recently been shown to be an HCMV DNA polymerase-associated stimulatory factor, a similar function is suggested for p41.

Amino Acid Sequence↗
PubMed1992

The Autographa californica baculovirus genome: evidence for multiple replication origins.

The Autographa californica multinucleocapsid nuclear polyhedrosis virus (AcMNPV), which is used for the overexpression of eukaryotic genes and is being engineered for possible use as a viral insecticide, has a circular, supercoiled genome of approximately 128 kilobases. Despite its widespread use, little is known about the mechanism by which AcMNPV replicates. Evidence is presented in this report that AcMNPV origins of DNA replication are repeated sequences each containing several closely related imperfect palindromes that are present in six regions distributed around the genome. Although AcMNPV infection-dependent plasmid replication was initiated by a single complete palindrome, the amount of replication was substantially increased in plasmids containing six or eight palindromes.

Baculoviridae↗
PubMed1991

Mapping of the epitopes of Epstein-Barr virus gp350 using monoclonal antibodies and recombinant proteins expressed in Escherichia coli defines three antigenic determinants.

The Epstein-Barr virus (EBV) major surface membrane antigen (MA), gp350/220, induces antibodies that neutralize virus infectivity in vitro. The MA glycoprotein is encoded by nucleotides 1784 to 4504 of the BamHI L fragment of the EBV genome. To define the antigenic epitopes on gp350, sequences encoding portions of the protein were cloned into an Escherichia coli expression system and eight recombinant clones were generated, two overlapping clones representing the C terminus and six overlapping clones representing the N terminus. The epitopes expressed by the recombinant proteins were mapped using 14 anti-MA monoclonal antibodies (MAbs) in a dot blot immunoassay. One of the MAbs reacted with clones that express the C terminus of gp350 and three others reacted with clones expressing the N terminal portion of the protein; the remaining MAbs tested were not reactive with the cloned proteins. The data identify three antigenic determinants on gp350. DNA sequences encoding these epitopes are located between nucleotides 1980 and 2307, 3186 and 3528, and 3528 and 3576 of the BamHI L fragment. In an attempt to elicit neutralizing antibodies, rabbits were immunized with gel-purified recombinant proteins from four of the clones. Neutralization assays indicate that the proteins expressed by these clones do not induce in vitro virus-neutralizing antibodies.

Animals↗
PubMed1989

Recombinant interferon-gamma in the treatment of recurrent nasopharyngeal carcinoma.

The etiologic relationship of the Epstein-Barr virus (EBV) to nasopharyngeal carcinoma prompted this study of the efficacy of interferon-gamma (IFN-gamma), which possesses antiviral and antitumor activity, in the treatment of recurrent carcinoma. Fourteen patients received recombinant IFN-gamma in daily intramuscular doses of 5-10 X 10(6) U/m2. Of 13 patients evaluable for response, five had a minor response; disease was stable in two and had progressed in six. EBV serology for immunoglobin (Ig) G, IgA-VCA, and early antigen was measured in six patients. In four of these, titers rose consistently with disease progression and in one patient, titers decreased with minor response.

Adult↗
PubMed1988

Association of the Epstein-Barr virus with lymphoepithelioma of the thymus.

A 30-year-old woman with the histologic diagnosis of lymphoepithelioma of the thymus is reported on. Investigation of Epstein-Barr serology showed evidence of infection, and Southern blot analysis showed the presence of the viral genome in the tumor specimen. The patient achieved complete remission after treatment with combination chemotherapy, autologous bone marrow transplant, and radiotherapy. These findings suggest that lymphoepithelioma of the thymus may have a viral pathogenesis similar to that of nasopharyngeal carcinoma.

Adult↗