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Biomedical subjects

D Fox

Publications and source records attributed to D Fox.

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

A comparison of driver behavior at railroad grade crossings with two different protection systems.

An observational study was conducted which compared the behavior of drivers at a railroad-highway grade crossing as trains approached. The effectiveness of a flasher-only protection system was compared with one incorporating flashers and barrier gates for a particular crossing. The addition of the gates significantly reduced the percentage of drivers crossing in front of trains from 67% to 38%. Plots of crossing probabilities showed them reduced as time until train arrival and the distance of the train from the crossing decreased. Train speed did not seem logically related to the probability of crossing perhaps because it is not well perceived. Drivers crossing around barrier gates tended to stop or slow on approach significantly less than those crossing with flashers only. It was suggested that the gates themselves provided an impediment to crossing which forced drivers inclined to cross into making a hurried and sometimes perilous decision. Their behavior was seen as explaining the surprisingly high number of accidents that occur at barrier-gate crossings. Discouraging drivers from driving around barrier gates was seen as essential if safety at these crossings was to be improved. Extending the length of gates and the education of the drivers regarding the law were seen as possible ways of increasing compliance.

Accidents, Traffic↗
PubMed1996

Functional characterization of the V1V2 region of human immunodeficiency virus type 1.

The level of proviral DNA sequence variation in the V1V2 region was monitored over time in six HIV-1-infected individuals. Substitutional and length variation was observed, where the majority of length changes, ranging from 28 to 49 amino acids, was located within the V1 region. Evidence for convergent evolution in the V2 region was found. The functional significance of this variation was assessed by cloning the V1V2 sequences into an infectious molecular clone, HXB2. The majority of chimeras replicated, demonstrating that the sequences, though genetically distinct, were capable of conferring a viable phenotype. Chimeras expressing closely related sequences in a constant genetic background displayed different biological phenotypes, with respect to both cytopathicity and cell tropism. However, no association between primary V1V2 amino acid sequence and viability or cytopathicity of the chimeric virus was observed, suggesting that predictions of virus phenotype based on sequences alone may be incorrect. The effect of V1V2 variation on the overall gp 120 conformation was measured by expressing the gp 20 from a number of viable and nonviable clones. No differences were observed, suggesting that misfolding of the chimeric gp 120 protein was not an explanation for the nonviability of some virus clones. Several chimeras were noncytopathic and only able to replicate in PBMC cultures, demonstrating that the V1V2 region, independent of the V3 sequence, is capable of defining both tropism and cytopathicity.

Amino Acid Sequence↗
PubMed1996

Thrombolysis with prourokinase versus urokinase: an in vitro comparison.

PURPOSE: Despite advantages demonstrated in vitro, no single thrombolytic agent has been clearly shown to be superior to another in the clinical setting. Prourokinase has recently received attention as a new thrombolytic agent with higher fibrin specificity. The thrombolytic activity of prourokinase, however, remains ill defined. The purpose of this study was to evaluate thrombolysis with prourokinase in comparison to urokinase in vitro. METHODS: We used an in vitro parallel channel perfusion model that simulates catheter-directed thrombolysis in the peripheral arterial system. Radiolabeled thrombi were subjected to 90 minutes of endhole catheter-directed infusion with either prourokinase 5000 IU/ml, urokinase 5000 IU/ml; or 5% dextrose in water at 4 ml/hr. RESULTS: Prourokinase and urokinase were found to be equivalent with respect to thrombolytic effect. Percent lysis was maximal at 90 minutes in both the urokinase and prourokinase groups. Prourokinase and urokinase were found to be equally effective in restoring flow through thrombosed graft segments. CONCLUSION: Prourokinase appears to offer little benefit over urokinase with respect to thrombolytic activity in an in vitro model that closely resembles the clinical setting. If prourokinase is to be accepted as an alternative to urokinase, advantages must relate to differences in fibrin specificity.

Catheterization↗
PubMed1996

Effects of prior testing with the WAIS-R NI on subsequent retest with the WAIS-R.

Seven subtests from the Wechsler Adult Intelligence Scale, Revised as a Neuropsychological Instrument (WAIS-R NI) were administered to 20 nonreferred university students. The same participants were administered the corresponding subtests from the WAIS-R 3 to 4 weeks later. Data concerning amount and consistency of change in 'scaled scores' were compared to those reported by Wechsler (1981) for test-retest with the WAIS-R. Performance on standard items was also compared to performance on multiple choice items from the WAIS-R NI. Gains observed in subtest 'scaled scores' at retest were comparable to those reported by Wechsler (1981). A substantial minority of participants obtained lower scores on some multiple choice items than they did on corresponding standard items. Implications and limitations of the current data, and the pressing need for comprehensive normative data for the WAIS-R NI are discussed.

Journal Article↗