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Biomedical subjects

C Gibbons

Publications and source records attributed to C Gibbons.

At least 19 recordsLinked to original sources
PubMed2005

Health Watch exposure estimates: do they underestimate benzene exposure?

A nested case-control study found that the excess of leukemia, identified among the male members of the Health Watch cohort, was associated with benzene exposure. Exposure had been retrospectively estimated for each individual occupational history using an algorithm in a relational database. Benzene exposure measurements, supplied by Australian petroleum companies, were used to estimate exposure for specific tasks. The tasks carried out within each job, the products handled, and the technology used, were identified from structured interviews with contemporary colleagues. More than half of the subjects started work after 1965 and had an average exposure period of 20 years. Exposure was low; nearly 85% of the cumulative exposure estimates were at or below 10 ppm-years. Matched analyses showed that leukemia risk increased with increasing cumulative benzene exposures and with increasing exposure intensity of the highest-exposed job. Non-Hodgkin lymphoma and multiple myeloma were not associated with benzene exposure. A reanalysis reported here, showed that for the 7 leukemia case-sets with greater than 16 ppm-years cumulative exposure, the odds ratio was 51.9 (5.6-477) when compared to the 2 lowest exposed categories combined to form a new reference category. The addition of occasional high exposures, e.g. as a result of spillages, increased exposure for 25% of subjects but for most, the increase was less than 5% of total exposure. The addition of these exposures reduced the odds ratios. Cumulative exposures did not range as high as those in comparable studies; however, the recent nature of the cohort and local handling practices can explain these differences.

Air Pollutants, Occupational↗
PubMed2004

Surgical wound infection as a performance indicator: agreement of common definitions of wound infection in 4773 patients.

OBJECTIVE: To assess the level of agreement between common definitions of wound infection that might be used as performance indicators. DESIGN: Prospective observational study. SETTING: London teaching hospital group receiving emergency cases as well as tertiary referrals. PARTICIPANTS: 4773 surgical patients staying in hospital at least two nights. MAIN OUTCOME MEASURES: Numbers of wound infections based on purulent discharge alone, on the Centers for Disease Control (CDC) definition of wound infection, on the nosocomial infection national surveillance scheme (NINSS) version of the CDC definition, and on the ASEPSIS scoring method. RESULTS: 5804 surgical wounds were assessed during 5028 separate hospital admissions. The mean percentage of wounds classified as infected differed substantially with different definitions: 19.2% with the CDC definition (95% confidence interval 18.1% to 20.4%), 14.6% (13.6% to 15.6%) with the NINSS version, 12.3% (11.4% to 13.2%) with pus alone, and 6.8% (6.1% to 7.5%) with an ASEPSIS score > 20. The agreement between definitions with respect to individual wounds was poor. Wounds with pus were automatically defined as infected with the CDC, NINSS, and pus alone definitions, but only 39% (283/714) of these had ASEPSIS scores > 20. CONCLUSIONS: Small changes made to the CDC definition or even in its interpretation, as with the NINSS version, caused major variation in estimated percentage of wound infection. Substantial numbers of wounds were differently classified across the grades of infection. A single definition used consistently can show changes in percentage wound infection over time at a single centre, but differences in interpretation prevent comparison between different centres.

Adult↗
PubMed2002

Re-assessing accumulated oxygen deficit in middle-distance runners.

The purpose of this study was to re-assess the accumulated oxygen deficit (AOD), incorporating recent methodological improvements i.e., 4 min submaximal tests spread above and below the lactate threshold (LT). We Investigated the Influence of the VO2 -speed regression, on the precision of the estimated total energy demand and AOD. utilising different numbers of regression points and including measurement errors. Seven trained middle-distance runners (mean +/- SD age: 25.3 +/- 5.4y, mass: 73.7 +/- 4.3kg. VO2max 64.4 +/- 6.1 mL x kg(-1) x min(-1)) completed a VO2max, LT, 10 x 4 min exercise tests (above and below LT) and high-intensity exhaustive tests. The VO2 -speed regression was developed using 10 submaximal points and a forced y-intercept value. The average precision (measured as the width of 95% confidence Interval) for the estimated total energy demand using this regression was 7.8mL O2 Eq x kg(-1) x min(-1). There was a two-fold decrease in precision of estimated total energy demand with the Inclusion of measurement errors from the metabolic system. The mean AOD value was 43.3 mL O2 Eq x kg(-1) (upper and lower 95% CI 32.1 and 54.5mL o2 Eq x kg(-1) respectively). Converting the 95% CI for estimated total energy demand to AOD or including maximum possible measurement errors amplified the error associated with the estimated total energy demand. No significant difference in AOD variables were found, using 10,4 or 2 regression points with a forced y-intercept. For practical purposes we recommend the use of 4 submaximal values with a y-intercept. Using 95% CIs and calculating error highlighted possible error in estimating AOD. Without accurate data collection, increased variability could decrease the accuracy of the AOD as shown by a 95% CI of the AOD.

Adult↗
PubMed2001

A bending wave simulator for investigating directional vibration sensing in insects.

Substrate vibrations are important in social and ecological interactions for many insects and other arthropods. Localization cues include time and amplitude differences among an array of vibration detectors. However, for small species these cues are greatly reduced, and localization mechanisms remain unclear. Here we describe a method of simulating the vibrational environment that facilitates investigation of localization mechanisms in small species. Our model species was the treehopper Umbonia crassicornis (Membracidae; length 1 cm), which communicates using bending waves that propagate along plant stems. We designed a simulator consisting of a length of dowel and two actuators. The actuators were driven with two time signals that created the relationship between slope and displacement characteristic of steady-state bending wave motion. Because the surface of the dowel does not bend, as would a natural stem, close approximation of bending wave motion was limited to a region in the center of the dowel. An example of measurements of the dynamic response of an insect on the simulator is provided to illustrate its utility in the study of directional vibration sensing in insects.

Animal Communication↗
PubMed2000

The rotary mechanism of ATP synthase.

Since the chemiosmotic theory was proposed by Peter Mitchell in the 1960s, a major objective has been to elucidate the mechanism of coupling of the transmembrane proton motive force, created by respiration or photosynthesis, to the synthesis of ATP from ADP and inorganic phosphate. Recently, significant progress has been made towards establishing the complete structure of ATP synthase and revealing its mechanism. The X-ray structure of the F(1) catalytic domain has been completed and an electron density map of the F(1)-c(10) subcomplex has provided a glimpse of the motor in the membrane domain. Direct microscopic observation of rotation has been extended to F(1)-ATPase and F(1)F(o)-ATPase complexes.

Models, Molecular↗
PubMed2000

The structure of the central stalk in bovine F(1)-ATPase at 2.4 A resolution.

The central stalk in ATP synthase, made of gamma, delta and epsilon subunits in the mitochondrial enzyme, is the key rotary element in the enzyme's catalytic mechanism. The gamma subunit penetrates the catalytic (alpha beta)(3) domain and protrudes beneath it, interacting with a ring of c subunits in the membrane that drives rotation of the stalk during ATP synthesis. In other crystals of F(1)-ATPase, the protrusion was disordered, but with crystals of F(1)-ATPase inhibited with dicyclohexylcarbodiimide, the complete structure was revealed. The delta and epsilon subunits interact with a Rossmann fold in the gamma subunit, forming a foot. In ATP synthase, this foot interacts with the c-ring and couples the transmembrane proton motive force to catalysis in the (alpha beta)(3) domain.

Animals↗
PubMed2000

Predictors of vaccination rates during a mass meningococcal vaccination program on a college campus.

Factors contributing to students' compliance with mass vaccination programs during meningococcal outbreaks have not been well described. A 1997 mass vaccination campaign at Michigan State University provided an opportunity to study such factors. Of 34,024 students in the target population, 17,538 (51.5%) were vaccinated in 5 days. Vaccination rates were higher for women (47.9%) than for men (43.1%) and higher for on-campus residents (65.3%) than for off-campus residents (35.6%). For each year of students' age beyond 19, the adjusted odds of vaccination were reduced by 0.82. Adjusted odds ratios for vaccination, with White students as the reference group at 1.0, were 1.33 for Asian American students, 0.97 (not significant) for Hispanic students, 0.82 for African American students, and 0.80 for Native American students. Students from the Colleges of Business, Engineering, Communication, and Natural Science had the highest vaccination rates; those from the College of Arts and Letters had the lowest rates.

Adult↗
PubMed1998

Biomedical equipment in the neonatal intensive care unit: is it a stressor?

The objective of this research was to learn more about nurses' perceptions of the sources of stress in a neonatal intensive care unit and based on the results, to initiate programs to combat stressors. Nurses were asked to complete a demographic sheet and stress audit. Thirty-three (52%) nurses responded and reported that their greatest source of stress was centered on bio-medical equipment--specifically on access, storage, design, and function issues. Nurses reported their least sources were advanced positions, stable infants, and routine procedures. Plans are underway to remedy equipment issues--primarily to inform and collaborate with others.

Adult↗
PubMed1997

Thy/Liv-SCID-Hu mice implanted with human intestine: an in vivo model for investigation of mucosal transmission of HIV.

Mucosal transmission is a major route by which individuals become infected with HIV. Investigation into the mechanism by which mucosal transmission of HIV occurs would be greatly facilitated by the development of a small animal model infectible with HIV by the mucosal route. We have previously described a SCID-hu mouse model, in which human thymic and liver tissues are implanted under both kidney capsules (thy/liv-SCID-hu mice), which are populated in the periphery with high numbers of human T cells and that develop disseminated HIV-1 infection after intraperitoneal injection. To expand further the usefulness of the thy/liv-SCID-hu mouse as a model for studying mucosal transmission of HIV, thy/liv-SCID-hu mice were subcutaneously implanted with human intestinal tissue in a manner that maintained the lumen. Four months later, the histological appearance of the implanted intestine resembled that of normal human bowel tissue and the lamina propria was populated with human T cells. Six weeks after introduction of HIV into the lumen of the intestinal implant, the mice developed disseminated HIV infection. Scattered HIV-infected cells were detected in the lamina propria of the implant, indicating that HIV infection in these mice was mediated by transmission of the virus across the mucosa of the human intestinal implant. Thus, our modified thy/liv-SCID-hu mice transplanted with human bowel tissue should provide a novel model for investigating mucosal transmission of HIV.

Animals↗
PubMed1987

Preservation of faecal continence during rises in intra-abdominal pressure: is there a role for the flap valve?

Studies were carried out in 15 normal subjects and 14 patients with idiopathic faecal incontinence to test whether a rectoanal flap valve could be responsible for maintaining faecal continence in man. Intraluminal pressures were recorded from the rectum and from three sites in the anal canal during serial increases in intra-abdominal pressure, produced by forced expiration into a sphygmomanometer keeping the height of the column of mercury at prescribed levels. The anal pressures in the normal volunteers always remained higher than the intrarectal pressures even when these were as high as 230 cm H2O. This pressure gradient was the reverse of that which would be found if an anterior rectal flap valve maintained continence and suggests instead that continence is normally maintained by a reflex contraction of the external anal sphincter. The anal pressures in patients with idiopathic faecal incontinence, however, fell below the rectal pressure as the intra-abdominal pressure increased, creating the conditions for a flap valve. The valve was incompetent, however, because fluid infused into the rectum leaked from the anus whenever the rectal pressure exceeded the anal pressure.

Adult↗
PubMed1987

Effect of stool size and consistency on defecation.

The ability of subjects to expel from the rectum objects simulating stools of different characteristics was assessed in paired studies carried out in a total of 58 normal subjects and 25 young women with severe constipation. Our results showed that a lower percentage of normal subjects and a lower percentage of constipated patients were able to pass a 1.8 cm incompressible sphere compared with a 50 ml deformable balloon, although constipated patients found it more difficult than normal subjects to expel both types of simulated stool. It was also more difficult for normal subjects to pass a soft compressible silicon rubber simulated stool than a stool made up of a similar volume of incompressible 1 cm wooden spheres contained in a cylindrical latex envelope, but both objects were much easier to pass than the same number of 1 cm spheres placed loose within the rectum. When normal subjects were instructed to expel single incompressible spheres of different sizes placed in the rectal ampulla, the intrarectal pressure and the time needed to pass these objects varied inversely with their diameter. These results suggest that more effort is required to expel stools from the rectum if they are small and hard than if they are large and soft.

Adult↗
PubMed1981

The management of advanced bladder carcinoma.

Since October 1978, 25 patients with metastatic carcinoma of the bladder have been treated with cis-platinum, doxorubicin hydrochloride and cyclophosphamide. Patient selection for this protocol was relatively strict and included only patients who had measurable parameters. All 3 drugs (60 mg./m.2 cis-platinum, 40 mg./m.2 doxorubicin hydrochloride and 400 mg./m.2 cyclophosphamide) were given as a single dose every 4 weeks. Over-all, 19 of the 23 evaluable patients (82 per cent) responded to therapy. There were 5 complete drug-induced remissions and 14 partial remissions. Generally, the treatment was tolerated well and common toxic effects were myelosuppression, nausea, vomiting and alopecia. One patient died of septicemia as a result of agranulocytosis. These promising results seem to indicate the high degree of effectiveness of this combination chemotherapy against transitional cell carcinoma of the bladder.

Aged↗
PubMedDate not supplied

A comparison of a computer and pencil and paper assignment.

Colleges are challenged to provide students with diverse teaching-learning experiences. Educators who introduce new teaching-learning experiences must evaluate the outcomes of these experiences. Three faculty members instituted a new multimedia computer-based assignment for undergraduate nursing students enrolled in a pediatric clinical course and then evaluated their knowledge and satisfaction. Students were asked to design a computer program about peripherally inserted central catheters, and to complete tests and summaries. During two semesters, 45 students participated in the assignment. As compared to another group of students who were asked to participate in a pencil and paper independent study assignment, these students were more satisfied with their computer assignment. Students in both groups, however, produced thought-provoking work and improved their knowledge base about central catheters. In many ways, the results support the use of a computer assignment.

Adult↗