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Biomedical subjects

L Evans

Publications and source records attributed to L Evans.

At least 73 records · Page 4Linked to original sources
PubMed1995

Quinolinic acid production is related to macrophage tropic isolates of HIV-1.

We sought to determine whether the neurotoxin quinolinic acid (QUIN) was produced by macrophages or lymphocytes infected with isolates of HIV-1 with varying degrees of macrophage tropism derived from patients with varying stages of AIDS dementia complex (ADC). Highly macrophage tropic isolates and minimally macrophage tropic isolates were used to inoculate macrophages and QUIN production was measured. Similarly, QUIN production from macrophages was monitored using a purified cell free highly macrophage tropic isolate and laboratory isolates SF33 and SF2. Each of these experiments was also performed with lymphocytes. We found that macrophages infected with macrophage tropic isolates of HIV-1 led to QUIN production while lymphocytes did not produce QUIN. The ability of the HIV-1 infected macrophages to produce QUIN was related to the viral inoculum and the degree of macrophage tropism of the isolate. The severity of ADC in the patient from whom a particular isolate was derived was not per se a determining factor for QUIN production. Purified cell free ADC isolates also led to QUIN production by macrophages thereby suggesting that HIV-1 infection alone is capable of inducing QUIN production.

AIDS Dementia Complex↗
PubMed1994

Pericentrin, a highly conserved centrosome protein involved in microtubule organization.

Antisera from scleroderma patients that react widely with centrosomes in plants and animals were used to isolate cDNAs encoding a novel centrosomal protein. The nucleotide sequence is consistent with a 7 kb mRNA and contains an open reading frame encoding a protein with a putative large coiled-coil domain flanked by noncoiled ends. Antisera recognize a 220 kd protein and stain centrosomes and acentriolar microtubule-organizing centers, where the protein is localized to the pericentriolar material (hence, the name pericentrin). Anti-pericentrin antibodies disrupt mitotic and meiotic divisions in vivo and block microtubule aster formation in Xenopus extracts, but do not block gamma-tubulin assembly or microtubule nucleation from mature centrosomes. These results suggest that pericentrin is a conserved integral component of the filamentous matrix of the centrosome involved in the initial establishment of organized microtubule arrays.

Amino Acid Sequence↗
PubMed1994

Driver injury and fatality risk in two-car crashes versus mass ratio inferred using Newtonian mechanics.

This paper aims at explaining the results of a recent empirical study that found that when cars of unequal mass crash into each other, the ratio of driver fatality risk in the lighter care to risk in the heavier car (the fatality risk ratio) increased as a power function of the ratio of the mass of the heavier car to that of the lighter car (the mass ratio). The present study uses two sources of information to examine the relationship between these same quantities: first, calculations based on Newtonian mechanics, which show that when two cars crash head-on into each other, the ratio of their changes in speed (delta-v) is inversely proportional to mass ratio; second, National Accident Sampling System data, which show how delta-v affects driver injury risk. The study is performed for fatalities and severe injuries and for unbelted and belted drivers. Combining the two sources of information gives the result that fatality risk ratio increases as a power function of mass ratio, the same functional form found in the empirical study. Because the study is rooted in Newtonian mechanics, it clearly and directly identifies physical mechanisms involved and leads to the conclusion that mass, as such, causes large differences in driver injury and fatality risk when cars of unequal mass crash into each other.

Accidents, Traffic↗
PubMed1994

Reliability of the DSM-III-R childhood anxiety disorders using structured interview: interrater and parent-child agreement.

OBJECTIVE: The aim of the study was to examine the interrater and parent-child agreement for the major child anxiety disorders. METHOD: One hundred sixty-one children and their parents underwent a semistructured interview (Anxiety Disorders Interview Schedule for Children). To increase external validity, clinicians did not receive specific, extensive training in diagnosing anxiety disorders apart from their standard qualifications. The design of the study allowed for calculation of agreement between raters based on information obtained from the parents alone, from the child alone, or through combined information from both the parents and child, and for calculation of agreement between information obtained from the parents and information obtained from the child. RESULTS: Levels of interrater agreement either as principal or additional diagnoses were moderate to strong for all of the major childhood anxiety disorders (kappa values .59 to .82). In contrast, parent-child agreement was poor for most diagnostic categories (kappa values .11 to .44). CONCLUSIONS: The data indicate that, despite the fact that parents and their children do not demonstrate strong agreement, the DSM-III-R childhood anxiety disorders can be reliably diagnosed by pairs of general clinicians using structured interviews.

Adolescent↗
PubMed1994

Car mass and fatality risk: has the relationship changed?

OBJECTIVES: The finding that the relative safety disadvantage of small compared with large cars is less for post-1980 cars than for pre-1980 cars has stimulated speculation that increasing fuel economy standards would increase fatalities less than previously expected. Fatal crashes between two cars of similar model year were examined to see whether this would be the case. METHODS: Driver fatality risk in relation to car mass was examined with Fatal Accident Reporting System data for crashes between two cars of a specific model year. RESULTS: The relative risk for driver fatality in the lighter car compared with the other driver's risk in a car 50% heavier was as follows: for 1966 through 1979 cars, the risk was between 3.7 and 5.1; for 1984 cars, 2.6; and for 1990 cars, 4.1. CONCLUSIONS: The results suggest that the lesser mass effect observed for mid-1980s cars occurred because improved crashworthiness features appeared in small cars earlier than in large cars. As all cars are redesigned, the relationship between risk and mass can be expected to approach that observed earlier in pre-1980 cars. If so, future fatality increases from fuel economy increases will be greater than estimated on the basis of mid-1980 data.

Accidents, Traffic↗
PubMed1993

How safe were today's older drivers when they were younger?

Data from the Fatal Accident Reporting System for 1975-1990 were used to perform longitudinal analyses of car driver fatality rates (driver fatalities per million population) for a 16-year period; for example, the fatality rate of drivers born in 1960 was examined for ages 15 years through 30 years. It was found that fatality rates for male drivers of a given age systematically decline with increasing birth year; for example, 20-year-olds born in 1970 have lower fatality rates than do 20-year-olds born in 1960. The fatality rates for cohorts of drivers of either sex do not begin to increase appreciably until about age 70 years, and then they approximately double by age 80 years. These increases are of a lesser magnitude, and occur later, than those found in the earlier cross-sectional analyses that identified the "older driver problem."

Accidents, Traffic↗
PubMed1993

Interstitial reirradiation for recurrent gynecologic malignancies: results and analysis of prognostic factors.

Thirteen patients with recurrent or new primary gynecologic malignancies after previous radiation therapy (RT) underwent interstitial reirradiation (IRI) from July 1986 through December 1990. Mean and median ages were 63 and 70 years, respectively. Mean and median implanted volumes were 14.3 and 12 cc, respectively. Overall, 9/13 (69%) had complete responses to IRI and 6 (46%) continue to have no evidence of disease (NED) 24-71 months later (median follow-up, 59 months). Of 7 patients with recurrent cervical or new primary vaginal carcinoma, 5 (71%) remain free of disease 27-71 months (median, 58 months) after IRI. Of 6 patients with recurrent endometrial carcinomas, only 1 (16%) continues with NED 24 months after IRI. Patients with NED after IRI had a median disease-free interval prior to IRI of 100 months compared to 6 months in patients failing IRI. Trends toward improved outcomes were observed in squamous vs adenocarcinoma, smaller tumor volumes, higher implant doses, and vaginal wall/suburethra vs vaginal cuff location. One possible complication, a rectovaginal fistula, developed in the presence of recurrent cervical cancer 22 months after IRI. Interstitial reirradiation is an effective treatment for selected patients with recurrent gynecologic malignancies after previous RT. Advantages of IRI over radical surgery include its potential to preserve organ structure and function and its applicability to patients with medical contraindications to salvage surgery. Furthermore, since subsequent exenterative surgery should not be compromised in patients failing IRI, a policy of IRI as initial treatment may be justified for patients in whom the potential for morbidity is limited.

Adult↗
PubMed1993

Defecation syncope secondary to functional inferior vena caval obstruction during a Valsalva maneuver.

This report describes a case of defecation syncope secondary to functional inferior vena cava (IVC) obstruction. Preoperative hemodynamic assessment revealed a marked decrease in blood pressure and IVC obstruction when the patient performed a Valsalva maneuver. The intraoperative approach included continuous hemodynamic monitoring as well as transesophageal ultrasonography to assess IVC patency during surgical mobilization of the IVC. Functional obstruction of the IVC at the diaphragmatic hiatus was identified, and this obstruction was relieved with extensive mobilization of the IVC and right crural myotomy. This report describes an effective surgical approach to a rare functional disorder involving the IVC.

Adult↗
PubMed1993

Mass ratio and relative driver fatality risk in two-vehicle crashes.

The relative risk, R, of a driver fatality in the lighter of two cars compared to the risk in the heavier is determined as a function of the ratio, mu, of the mass of the heavier to that of the lighter, using Fatal Accident Reporting System data for 1975-1989. In all of many cases investigated, the data fitted well the functional relationship R = A mu u. When the cars differ only in mass, A = 1; if they differ in another dichotomous characteristic, such as old compared to new model years, A estimates the influence of this other characteristic when the masses are equal. The results show that if a driver transfers to a car lighter by 1%, that driver's fatality risk in a two-car crash compared to the risk to the other involved driver increases by between 2.7% and 4.3%, the specific value depending on other factors, such as model year. When one car crashes head-on into the side of another of equal mass, driver fatality risk in the side-impacted car compared to that in the frontally impacted car is 4.5 +/- 0.6 times as great for right-side impacts and 10.1 +/- 1.7 times as great for left-side impacts. Extending the analysis to vehicles other than cars provides empirical evidence that two previously stated "laws" apply systematically over a wide spectrum of vehicles, from mopeds, through motorcycles, small cars, large cars, small trucks to large trucks. These laws are that, when other factors are equal, (1) the lighter the vehicle, the less risk to other road users, and (2) the heavier the vehicle, the less risk to its occupants.

Accidents, Traffic↗
PubMed1993

Impact of bone density corrections on target dose delivered to the prostate with 4 MV, 6 MV, 10 MV, and 18 MV photons.

Doses for definitive prostate irradiation have been derived empirically using low-energy megavoltage equipment without availability of bone density corrections. With their increased availability, higher energy photons are being used more frequently because of their improved depth of penetration. Although inhomogeneity corrections lead to greater accuracy of dose delivery, the clinical utility of corrections in the pelvis is unclear. This study evaluates the effect of bone density on the dose delivered with respect to the photon energy employed. Contours and volumes for 10 patients were taken from computed tomography scans at the center of the prostate gland. Treatment plans for bilateral prostate arc fields were run on the Capintec Treatment Planning System for 4, 6, 10, and 18 MV photon energies. The monitor units needed to deliver 6500 cGy to isocenter without bone correction were used for calculations, both with and without bone correction using the equivalent path length algorithm. The median dose to the isocenter was 6500 cGy for all energies without bone correction. The median doses using the uncorrected monitor units for the 4 MV, 6 MV, 10 MV, and 18 MV photon beams corrected for bone density were 6033, 6062, 6166, and 6228 cGy, respectively. The variance in target doses observed in our patient sample was +/- 2.3%, +/- 2.2%, +/- 1.7%, and +/- 1.4%, respectively, for the 4 MV, 6 MV, 10 MV, and 18 MV beams with bone correction. The increased density of bone in the pelvis does alter the actual dose to the prostate from external beam treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Bone Density↗
PubMed1993

Alcohol's effect on fatality risk from a physical insult.

Although alcohol's effect on the risk of being involved in a traffic crash is well known, its influence on the risk of death, given that a crash has occurred, is more uncertain. One study published a few years ago finds that alcohol increases such risk. The present study examines alcohol's effect on fatality risk in a crash using data and methods independent of the previous study, and provides estimates as a function of blood alcohol concentration (BAC). Data for drivers with measured BAC who were fatally injured in a two-car crash were selected from the Fatal Accident Reporting System (FARS). The study uses two sets of fatal crashes. For one, the probability that a BAC = 0 driver was killed is low, so that if alcohol increased fatality risk, this would generate additional fatalities at higher BAC levels. For the other set of crashes, fatality risk was sufficiently close to 100% that other factors had little opportunity to influence it. Dividing the fatalities that can be affected by alcohol by those that cannot measures alcohol's influence on fatality risk, and gives that a driver with BAC = 0.1% is 1.9 +/- 0.2 times as likely as is a BAC = 0 driver to be killed in the same crash. The corresponding ratio for a BAC = 0.25% driver is 3.3 +/- 0.5. While derived using the "laboratory" of traffic, there does not appear to be any obvious reason why the results should not apply to physical trauma in general, so a BAC of 0.1% doubles the risk of death from a given impact, and a BAC of 0.25% triples the risk.

Accidents, Traffic↗
PubMed1993

Hospitalized elders. Risk of confusion with hip fracture.

Although frequently underdiagnosed, more than half of all patients admitted for the treatment of hip fracture are confused at the time of hospital admission or develop confusion sometime during the course of hospitalization. This study reveals the profound vulnerability of severely confused patients with hip fracture. Severely confused patients experience higher overall rates of medical complications and are more likely to be discharged to a nursing home. In addition to being at higher risk for medical complications, severely confused patients also appear to be at greater risk for being physically restrained.

Aged↗
PubMed1992

Long-term symptomless HIV-1 infection in recipients of blood products from a single donor.

There have been reported cases of long-term symptomless human immunodeficiency virus type 1 (HIV-1) infection, but it is not clear whether the benign course of infection was due to host, viral, or other unknown factors. During follow-up of subjects with transfusion-acquired HIV-1 infection in New South Wales, Australia, we identified a group of 6 subjects who had been infected through a single common donor. We were therefore able to study the contributions of various factors to the course of infection. Throughout follow-up (range 6.8-10.1 years after infection), 5 of the recipients and the donor (last follow-up 10.2 years after infection of the first recipient) remained clinically free of symptoms, with normal CD4 cell counts and no p24 antigenaemia. HIV-1 was isolated from only 1 recipient; the isolate did not induce syncytia in a SUPT1 co-culture assay and had a limited in-vitro host range. 1 infected recipient (who had received extensive immunosuppressive treatment for systemic lupus erythematosus) developed Pneumocystis carinii pneumonia and died 4.3 years after infection. The frequency of progression to AIDS or a CD4 cell count below 0.50 x 10(9)/l was significantly lower among the 6 subjects with a common donor (1/6) than among 101 other HIV-infected transfusion recipients for whom data from 7 years of follow-up were available (94/101; p less than 0.0001). These findings suggest that the subjects were infected by a less virulent strain of HIV-1. The identification of this group of subjects should stimulate a search for other similar groups, which will provide important information on the immunopathogenesis of HIV-1 disease.

Acquired Immunodeficiency Syndrome↗