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Biomedical subjects

J Stone

Publications and source records attributed to J Stone.

At least 127 records · Page 7Linked to original sources
PubMed1998

The natural history of human papillomavirus infection as measured by repeated DNA testing in adolescent and young women.

OBJECTIVES: The objectives of this study were to describe the early natural history of human papillomavirus (HPV) infection by examining a cohort of young women positive for an HPV test and to define within this cohort (1) the probability of HPV regression, (2) the risk of having a squamous intraepithelial lesion, and (3) factors that were associated with HPV regression. STUDY DESIGN: The study was a cohort analytic design. An inception cohort of 618 women positive for HPV participated. HPV testing, cytologic evaluation, and colposcopic evaluation were performed at 4-month intervals. HPV testing was characterized for two groups: low risk (five types rarely associated with cancers) and high risk (nine types most commonly associated with cancers). RESULTS: Estimates provided by Kaplan-Meier curves showed that approximately 70% of women were found to have HPV regression by 24 months. Women with low-risk HPV type infections were more likely to show HPV regression than were women with high-risk HPV type infections (log rank test p = 0.002). The relative risk for the development of high-grade squamous intraepithelial lesion (HSIL) was 14.1 (95% confidence interval: 2.3, 84.5) for women with at least three positive tests for high-risk HPV preceding the development of the HSIL compared with that for women with negative tests for high-risk HPV. However, 88% of women with persistent positive HPV tests have not had HSIL to date. No factors associated with high-risk HPV type regression were identified except for a negative association with an incident history of vulvar condyloma (relative risk = 0.5 [95% confidence interval: 0.3 to 0.8]). CONCLUSION: Most young women with a positive HPV test will become negative within a 24-month period. Persistent positive tests with oncogenic HPV types represented a significant risk for the development of HSIL. However, we found that most young women with persistent positive HPV tests did not have cytologically perceptible HSIL over a 2-year period. Factors thought to be associated with the development of HSIL were found not to be important in HPV regression.

Adolescent↗
PubMed1998

An ultrastructural and systemic analysis of glycosaminoglycans in thyroid-associated ophthalmopathy.

PURPOSE: To determine the ultrastructural localisation of glycosaminoglycans (GAGs) in the extraocular muscles (EOMs) of patients with thyroid-associated ophthalmopathy (TAO) and to see whether the quantity and type of GAGs present in blood and urine are markers of the disease. METHODS: Biopsies of affected EOMs were taken and studied by transmission electron microscopy (TEM). These were either fixed conventional for TEM, or in 0.5% tannic acid and others for immunogold staining. Serum hyaluronan (HA) was measured using a radioimmunoassay in patients with TAO as well as control subjects, and urinary GAG levels assessed by photometric quantitation of hexuronic acid after reaction with carbazole. The excretion pattern of the urinary GAGs was determined by discontinuous electrophoresis. RESULTS: TEM showed that there is a marked expansion of the endomysial space in TAO EOM biopsies as compared with non-TAO strabismus specimens. This is caused by an increased number of collagen fibres, interspersed with a granular amorphous material surrounding striated collagen fibres shown to be hyaluronan by immunogold staining. In contrast, serum hyaluronan concentrations were similar in TAO and control patients, although there was a statistically significant difference in the urinary GAG excretion between the two groups of patients examined. By discontinuous electrophoresis, chondroitin sulphate and heparan sulphate were present in both patients and controls. CONCLUSION: GAGs and in particularly HA are present at the EOM level in patients with recently inactive TAO. However, serum levels of HA and urinary GAGs are not sensitive indicators for their presence within the EOMs.

Adult↗
PubMed1998

Using a nonrecursive formula to determine cladogram probabilities.

Three properties of bifurcating branching diagrams that are used for representing a specific number of taxa are (1) the number of possible arrangements, (2) the number of possible topologies, and (3) the probabilities of formation according to particular models of cladogenesis. Of these, the probabilities have received the least attention in the literature. Indeed, many biologists would be astonished by the observation that the probability of a commonly cited cladogram containing 35 phyla of the animal kingdom is < 0.0072% of the value of the average probability taken over all possible cladograms! We reviewed works on cladogram arrangements and topologies and developed a computer-generated table of enumerations that extends and corrects such tables in the literature. We also developed a nonrecursive formula for the determination of cladogram probabilities. This formula facilitates calculation and thereby should promote use of cladogram probabilities, which might provide more accurate null hypotheses for tests of cladogenic events than do considerations of cladogram arrangements or topologies.

Animals↗
PubMed1998

Effect of fluconazole on indinavir pharmacokinetics in human immunodeficiency virus-infected patients.

To evaluate a potential pharmacokinetic interaction of coadministration of fluconazole, and indinavir, a human immunodeficiency virus (HIV) protease inhibitor, 13 patients were enrolled in a multiple-dose, three-period, placebo-controlled, crossover study. Patients were randomly assigned to receive indinavir at 1,000 mg every 8 h for 7 1/3 days (with fluconazole placebo), fluconazole at 400 mg once daily for 8 days (with indinavir placebo), and indinavir with fluconazole in combination. The pharmacokinetics of both drugs were measured on day 8 of each treatment period. The peak concentration in plasma (Cmax) and the time to reach Cmax were obtained by inspection, and the area under curve (AUC) was calculated for indinavir and fluconazole for each treatment period in which the respective drugs were administered. There was a marginally (P = 0.08) statistically significant decrease in the AUC from 0 to 8 h (AUC(0-8)) for indinavir when it was administered with fluconazole. However, the magnitudes of the decreases in Cmax and the concentration at 8 h postdosing (C8) were not as great as the decrease in AUC(0-8). Although the 90% confidence interval for the geometric mean ratio was within the hypothesized limits, the clinical significance is not clear. Indinavir coadministration with fluconazole had no statistically (P > 0.5) or clinically significant effect on the Cmax and C8 of indinavir. Fluconazole coadministration with indinavir had no statistically or clinically significant effect on the pharmacokinetics of fluconazole. One patient was discontinued because of mild to moderate abdominal pain and diarrhea while on indinavir and fluconazole in combination. No serious adverse experience according to the results of laboratory tests was noted. Total bilirubin levels in serum were mildly increased in most patients treated with indinavir. This was not clinically significant and was not affected by the coadministration of fluconazole. Although the values of the pharmacokinetic parameters for indinavir decrease in the presence of fluconazole, indinavir and fluconazole can be administered concomitantly to HIV-infected patients without adjustment of the dose of either drug, and both drugs are generally well tolerated.

Adolescent↗
PubMed1998

Photoreceptor dystrophy in the RCS rat: roles of oxygen, debris, and bFGF.

PURPOSE: To examine the roles of oxygen, basic fibroblast growth factor (bFGF), and photoreceptor debris in the photoreceptor dystrophy of the Royal College of Surgeons (RCS) rat. METHODS: Pups were exposed during the critical period of their development (postnatal day [P] 16-24) and for some days thereafter to hypoxia and hyperoxia. The effects of these exposures on photoreceptor death, debris accumulation in the subretinal space, and the expression of bFGF protein and mRNA by surviving cells were studied. RESULTS: During the critical period hyperoxia slowed photoreceptor death in a dose-related fashion and decreased bFGF protein levels, whereas hypoxia accelerated death and increased bFGF levels. At the edges of the retina, where photoreceptors survive longest in normoxia, hypoxia had little effect on either photoreceptor death or bFGF protein levels. Oxygen-induced modulation of rates of death could not be related to the accumulation of debris in the subretinal space. After P27, the relationship between oxygen and photoreceptor death changed markedly, hyperoxia no longer delaying and hypoxia no longer accelerating death. CONCLUSIONS: The death of RCS rat photoreceptors in the period P16 to P27 is precipitated by hypoxia that may result from the accumulation of photoreceptor debris in the subretinal space. This debris, the result of the phagocytotic failure of the retinal pigment epithelium in this strain, lies in the normal pathway of oxygen diffusing to the photoreceptors from the choriocapillaris. During this period the retina responds to hypoxia by increasing expression of a potentially protective protein (bFGF), but hypoxia-induced damage overwhelms any protection provided by this or other mechanisms. Later stages of the dystrophy may not be hypoxia-induced.

Animals↗
PubMed1997

Biomechanical evaluation of posterior cervical stabilization after a wide laminectomy.

STUDY DESIGN: In vitro biomechanical investigation with nondestructive and destructive testing in a human cadaveric model simulating a wide postlaminectomy condition. OBJECTIVES: To determine the relative stability conferred by a posterior cervical spinal rod system and posterior cervical plating. SUMMARY OF BACKGROUND DATA: Posterior cervical plate fixation has been shown to be biomechanically superior to wiring techniques, but lateral mass screws may injure neurovascular structures or facet joints if they are inserted improperly. A cervical rod system has been developed to enhance the safety of lateral mass instrumentation. METHODS: The cervical spines of 12 cadavers underwent biomechanical testing. After completion of the nondestructive intact testing, a wide laminectomy with subtotal facetectomies from C4 to C6 was performed. The specimens in two subgroups (group A, cervical spine rods with unicortical fixation, and group B, reconstruction plates with bicortical fixation) were tested in flexion, lateral bending, and torsion. Finally, destructive testing in flexion was performed. Stiffness, neutral zone, failure moment, energy to failure, and mechanism of failure were determined for each specimen. The data were analyzed using paired t tests and ANOVA. RESULTS: Group B had a greater mean screw torque value. The instrumented constructs had a greater stiffness ratio (instrumented/intact) than the intact specimens in flexion, lateral bending, and torsional testing. Group A had a significantly greater flexural stiffness than Group B. Neutral zone ratio values were significantly lower during flexural testing for the cervical rod construct. Destructive testing resulted in significantly greater failure moment and energy-to-failure values for group A. In the cervical rod construct, failure occurred primarily by superior screw loosening with pull-out from the lateral mass. Reconstruction plates consistently failed with fracture of the lateral mass and superior screw loosening. CONCLUSION: Significantly greater stability was noted in the cervical rod construct during nondestructive and destructive flexural testing.

Adult↗
PubMed1997

Development of the human retinal vasculature: cellular relations and VEGF expression.

We have investigated the relationships of the cellular constituents of the retinal vasculature--astrocytes, microglia and pericytes--to the differentiating endothelium in human fetal retina. The vascular endothelium was stained using NADPH-diaphorase histochemistry in 12 human fetal retinae ranging in gestational age from 15-22 weeks. Specimens were double labeled using antibodies against glial fibrillary acid protein, alpha smooth muscle actin, or major histocompatibility complex class II antigens to label astrocytes, contractile cells and microglia, respectively. In addition, specimens of 12, 14, 16 and 20 weeks gestation were hybridized in situ for VEGF expression. In retinal wholemounts the vascularized area comprised four lobes that converged on the optic disc. The vascular network was more dense in the temporal lobes than in the nasal lobes, and different growth patterns were evident. Astrocytes were distributed in two layers--one associated with the optic axons and a deeper layer associated with the developing vessels. In retinae younger than 20 weeks, astrocytes in the deep layer were only loosely associated with the developing vessels and extended as far as 150 microns ahead of the most peripheral vessels. A closer register between retinal vessels and the distribution of astrocytes was evident in the nasal region of retinas older than 20 weeks. In situ hybridization demonstrated expression of VEGF mRNA in the vascular layer, superficial to the ganglion cell layer, at the margins of the vascularized zone. Differences were evident in the density of astrocyte coverage of developing vessels and in the extent of VEGF expression in different regions of the retina: the relationship of these differences to differentiation gradients in the neural retina is discussed. Intensely immunoreactive microglia were observed in the vascular layer, associated with the vascular endothelium as far as the most peripheral loops, but not beyond. Alpha smooth muscle actin-containing cells covered the proximal parts of large arteries, but not corresponding veins; they were absent from arterial side-arm branches, as well as the newly formed and small diameter vessels in the age range studies. The results suggest that microglia, contractile cells and astrocytes have distinct temporo-spatial relationships to the differentiating vascular endothelium in human retinas and that VEGF expression at the vascular front, presumably by astrocytes, is associated with the spread of the retinal vasculature, as described in other species.

Cell Differentiation↗
PubMed1997

Database challenges and solutions in neuroscientific applications.

In the scientific community, the quality and progress of various endeavors depend in part on the ability of researchers to share and exchange large quantities of heterogeneous data with one another efficiently. This requires controlled sharing and exchange of information among autonomous, distributed, and heterogeneous databases. In this paper, we focus on a neuroscience application, Neuroanatomical Rat Brain Viewer (NeuART Viewer) to demonstrate alternative database concepts that allow neuroscientists to manage and exchange data. Requirements for the NeuART application, in combination with an underlying network-aware database, are described at a conceptual level. Emphasis is placed on functionality from the user's perspective and on requirements that the database must fulfill. The most important functionality required by neuroscientists is the ability to construct brain models using information from different repositories. To accomplish such a task, users need to browse remote and local sources and summaries of data and capture relevant information to be used in building and extending the brain models. Other functionalities are also required, including posing queries related to brain models, augmenting and customizing brain models, and sharing brain models in a collaborative environment. An extensible object-oriented data model is presented to capture the many data types expected in this application. After presenting conceptual level design issues, we describe several known database solutions that support these requirements and discuss requirements that demand further research. Data integration for heterogeneous databases is discussed in terms of reducing or eliminating semantic heterogeneity when translations are made from one system to another. Performance enhancement mechanisms such as materialized views and spatial indexing for three-dimensional objects are explained and evaluated in the context of browsing, incorporating, and sharing. Policies for providing the system with fault tolerance and avoiding possible intellectual property abuses are presented. Finally, two existing systems are evaluated and compared using the identified requirements.

Animals↗
PubMed1997

Inadequate calcium, folic acid, vitamin E, zinc, and selenium intake in rheumatoid arthritis patients: results of a dietary survey.

OBJECTIVES: To determine the adequacy of calcium, folic acid, vitamin E, zinc, and selenium intake in patients with rheumatoid arthritis (RA). METHODS: We conducted an observational study on 48 patients (13 men, 35 women; mean age, 64.5 years) with RA attending a specialty clinic in New Zealand comparing their dietary intake as measured by a 5-day dietary survey with recommended dietary intake (RDI) guidelines. Information on disease activity, functional ability, and drug therapy also was obtained. RESULTS: The percentage of patients who achieved the RDI was 23% for calcium, 46% for folic acid, 29% for vitamin E, 10% for zinc, and only 6% for selenium. Patients on methotrexate had a significantly reduced intake of folic acid as a percentage of RDI (P < .05) compared with those on other therapies. In contrast, dietary intake of iron and protein was largely adequate and unrelated to anemia. CONCLUSIONS: Patients with RA should receive dietary education or supplementation to bring their intake of calcium, folic acid, vitamin E, zinc, and selenium up to the RDI.

Adult↗
PubMed1997

When exemplification fails: hypocrisy and the motive for self-integrity.

Two experiments investigated how the dissonance that follows a hypocritical behavior is reduced when 2 alternatives are available; a direct strategy (changing behavior to make it less hypocritical) or an indirect strategy (the affirmation of an unrelated positive aspect of the self). In Experiment 1, after dissonance was aroused by hypocrisy, significantly more participants chose to reduce dissonance directly, despite the clear availability of a self-affirmation strategy. In Experiment 2, participants again chose direct resolution of their hypocritical discrepancy, even when the opportunity to affirm the self held more importance for their global self-worth. The discussion focuses on the mechanisms that influence how people select among readily available strategies for dissonance reduction.

Adult↗
PubMed1997

Long-term survival advantage of MACOP-B over CHOP in intermediate-grade non-Hodgkin's lymphoma. The Australian and New Zealand Lymphoma Group.

BACKGROUND: The initial publication of the results of the Australian and New Zealand Lymphoma Group (ANZLG) randomized controlled trial comparing MACOP-B and CHOP in patients with intermediate-grade non-Hodgkin's lymphoma (NHL) showed equivalent complete response rates, time to treatment failure, and survival. Here we report the long-term follow-up of the 236 patients entered on that study to determine if there were any long-term advantages or disadvantages associated with MACOP-B. PATIENTS AND METHODS: Two hundred thirty-six eligible patients were randomized between October 1986 and June 1991. The median duration of follow-up has been extended from 3.2 years in our previous publication to 6.5 years. RESULTS: As previously reported, the complete response (CR) rate for MACOP-B and CHOP chemotherapy was 51% and 59%, respectively. The estimated failure-free survival rate for MACOP-B and CHOP patients was 42% and 30%, respectively, at 5 years (P = 0.045) and 37% and 25%, respectively, at 8 year (P = 0.057). The estimated overall survival rate at 5 years was 54% for MACOP-B and 41% for CHOP patients (P = 0.035) and at 8 years was 45% and 36%, respectively (P = 0.16). CONCLUSION: With this extended follow-up, we have shown a long-term survival advantage for MACOP-B chemotherapy over standard CHOP in patients with intermediate-grade non-Hodgkin's lymphoma.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1997

Role of astrocytes in the control of developing retinal vessels.

PURPOSE: To assess the role of astrocytes in controlling the growth of developing retinal vessels. METHODS: Growth of retinal vessels in the neonatal rat retina was examined in three conditions: normal development, cyclic hyperoxia, and normoxia (1 day 70% to 75% oxygen, 1 day room air for up to seven cycles from birth, and room air for up to 16 days), and direct hypoxia (10% oxygen from postnatal day 3 [P3]). Retinas were examined as wholemounts labeled for astrocytes, microglia, and blood vessels and in some experiments for the fragmentation of DNA characteristic of apoptosis. RESULTS: In normoxia, superficial retinal vessels formed to the processes of astrocytes. In cyclic hyperoxia, the depletion of superficial retinal vessels and subsequent neovascularization described by others were confirmed. The neovascularization was preceded by the depletion by apoptotic death of the astrocyte population, first between vessels but eventually breaching the glia limitans along vessels. The earliest forms of neovascularization resembled microaneurysms, each protruding through a defect in the glia limitans of a capillary. Neurons of the ganglion cell layer survived. Direct hypoxia from P3 caused hypertrophy of superficial vessels. Between P3 and P6, some vessels accelerated past the still-spreading astrocytes, often growing out of the retina into the vitreous humor. Direct hypoxia also caused astrocyte degeneration, but capillaries retained astrocyte investment and were not the site of vascular damage. By P8, breaches in the astrocytic glia limitans became prominent but were restricted to large veins. At such breaches, bleeding into the vitreous humor was common. CONCLUSIONS: Retinal vessels normally develop in close association with astrocytes. Where that association is broken, preretinal vessels may grow or bleed into the vitreous humor. Astrocytes play important roles in constraining retinal vessels to the retina and in maintaining their integrity.

Animals↗