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Biomedical subjects

M A Stevens

Publications and source records attributed to M A Stevens.

At least 19 recordsLinked to original sources
PubMed2004

Assessing the health implications of turbidity and suspended particles in protected catchments.

The supply of unfiltered disinfected drinking water from Melbourne's fully protected catchments means that the water-quality managers must ensure that the source water poses no public health risk. High turbidity is currently used as a surrogate of pathogens, and harvesting of water is based on its measurement. The work presented here summarises suspended particle and associated pathogen, microbial indicator and faecal biomarker concentrations collected to (a) quantify turbidity in an Australian water supply system and (b) assess the possibility of increasing water harvesting from selected tributaries. Pathogens and microbial indicators were present in low numbers in these source waters; increased turbidity during storm events was not associated with an increase in pathogen concentration. The results confirmed that protected catchments, along with good management, were effective barriers to pathogen contamination. Aesthetic issues still need to be addressed, but no measurable increase in microbiological risk was associated with storm-generated particles.

Bacteria↗
PubMed2001

Effect of knowledge of chronologic age on the variability of pediatric bone age determined using the Greulich and Pyle standards.

OBJECTIVE: The purpose of this study was to investigate the impact of knowing chronologic age on the variability of pediatric bone age determination using the method of Greulich and Pyle. MATERIALS AND METHODS: Radiographs of the left hand of 107 patients were interpreted by four radiologists on two separate occasions, once with and once without knowledge of the patient's chronologic age at time of interpretation. Twenty-five radiographs were randomly selected and reevaluated twice by each radiologist. Interobserver and intraobserver variability were calculated and compared for the two conditions. The distribution of studies with normal and abnormal findings was then compared across knowledge conditions for all observers and by individual observer, using two standard deviations above and below chronologic age as the range of "normal". RESULTS: When the chronologic age was known, the interobserver reliability coefficient for knowledge of chronologic age was 0.954 and when not known, 0.952. The intraobserver reliability coefficients when chronologic age was known ranged from 0.944 to 0.967, and when not known from 0.938 to 0.980. Observers interpreted 58% (248/428) of the radiographs as having normal findings when chronologic age was known and 48% (205/428) when chronologic age was not known. CONCLUSION: Knowing chronologic age before assessing bone age radiographs does not affect the reproducibility of assessment. However, observers are more likely to interpret the radiograph as showing normal findings when chronologic age is known than if the interpretation is performed with the observer unaware of chronologic age.

Adolescent↗
PubMed1999

A prospective randomized trial of prevention measures in patients at high risk for contrast nephropathy: results of the P.R.I.N.C.E. Study. Prevention of Radiocontrast Induced Nephropathy Clinical Evaluation.

OBJECTIVES: This study was done to test the hypothesis that a forced diuresis with maintenance of intravascular volume after contrast exposure would reduce the rate of contrast-induced renal injury. BACKGROUND: We have previously shown a graded relationship with the degree of postprocedure renal failure and the probability of in-hospital death in patients undergoing percutaneous coronary intervention. Earlier studies of singular prevention strategies (atrial natriuretic factor, loop diuretics, dopamine, mannitol) have shown no clear benefit across a spectrum of patients at risk. METHODS: A prospective, randomized, controlled, single-blind trial was conducted where 98 participants were randomized to forced diuresis with intravenous crystalloid, furosemide, mannitol (if pulmonary capillary wedge pressure <20 mm Hg), and low-dose dopamine (n = 43) versus intravenous crystalloid and matching placebos (n = 55). RESULTS: The groups were similar with respect to baseline serum creatinine (2.44+/-0.80 and 2.55+/-0.91 mg/dl), age, weight, diabetic status, left ventricular function, degree of prehydration, contrast volume and ionicity, and extent of peripheral vascular disease. The forced diuresis resulted in higher urine flow rate (163.26+/-54.47 vs. 122.57+/-54.27 ml/h) over the 24 h after contrast exposure (p = 0.001). Two participants in the experimental arm versus five in the control arm required dialysis, with all seven cases having measured flow rates <145 ml/h in the 24 h after the procedure. The mean individual change in serum creatinine at 48 h, the primary end point, was 0.48+/-0.86 versus 0.51+/-0.87, in the experimental and control arms, respectively, p = 0.87. There were no differences in the rates of renal failure across six definitions of renal failure by intent-to-treat analysis. However, in all participants combined, the rise in serum creatinine was related to the degree of induced diuresis after controlling for baseline renal function, r = -0.36, p = 0.005. The rates of renal failure in those with urine flow rates greater than 150 ml/h in the postprocedure period were significantly lower, 8/37 (21.6%) versus 28/61 (45.9%), p = 0.03. CONCLUSIONS: Forced diuresis with intravenous crystalloid, furosemide, and mannitol if hemodynamics permit, beginning at the start of angiography provides a modest benefit against contrast-induced nephropathy provided a high urine flow rate can be achieved.

Aged↗
PubMed1999

Residual oil fly ash amplifies allergic cytokines, airway responsiveness, and inflammation in mice.

Particulate matter (PM) air pollution may increase symptom severity in allergic asthmatics. To examine possible interaction, or greater than additive responses, between PM effects and allergic responses, an ovalbumin-sensitized and challenged (OVA) mouse model of allergic airways disease was utilized. After challenge, mice were intratracheally instilled with saline vehicle or 3 mg/kg (approximately 60 microg) residual oil fly ash (ROFA), a transition metal-rich emission source PM sample. Physiological and inflammatory responses were examined 1, 3, 8, and 15 d later. In response to intravenously administered methacholine, ROFA increased total respiratory system resistance and decreased compliance 1 d after exposure, whereas effects of OVA lasted at least 15 d after exposure. Significant interactions between OVA and ROFA were mainly observed 8 d after challenge and exposure, especially with respect to compliance. A strong interaction (p < 0.01) between OVA and ROFA exposure resulted in 8-fold (1 d) and 3-fold (3 d) increases in bronchoalveolar lavage (BAL) fluid eosinophil numbers. A similarly strong interaction (8-fold) was observed in BAL fluid interleukin-4 (IL-4) 1 d after challenge and exposure. Significant though less strong interactions were also found with respect to IL-4 and IL-5 by 3 d postchallenge/exposure. This study shows that allergen challenge and exposure to emission source particulate matter containing relatively high levels of transitions metals can interact to increase Th2 cytokine production, eosinophil recruitment, and airway hyperresponsiveness in previously sensitized mice.

Air Pollutants↗
PubMed1999

Case report: paraarticular soft-tissue osteoma of the hip.

A case of paraarticular soft-tissue osteoma of the hip is presented. The patient is a 30-year-old white male with a two year history of progressive left hip pain. Plain film and cross-sectional imaging in conjunction with pathologic correlation are used to make the diagnosis. The lesion lacks the typical zoning pattern of myositis ossificans, shows no direct communication with native bone, and is extraarticular in location as opposed to synovial osteochondromatosis. Soft tissue osteomas most commonly occur around the knee, the foot, and the ankle. Soft tissue osteomas are rare tumors and this case is unusual in that it occurs around the hip.

Adult↗
PubMed1996

Ozone uptake in healthy adult males during quiet breathing.

Experimental measurements of ozone (O3) uptake are needed for validation of dosimetry model parameters and in predictions as well as for determining factors affecting uptake and for making comparisons between subpopulations or across species. In this study, 10 healthy adult male subjects were exposed to 0.3 ppm O3 while seated and breathing naturally through the nose or mouth. Total respiratory tract O3 uptake, spontaneous breathing parameters, and respiratory gas exchange were measured for 10 min under steady-state conditions. The exposure protocol was replicated in each subject approximately 2 weeks after the first visit. On each visit, health exams were performed and spirometric lung measurements were obtained. The experimental design provided comparisons of total O3 uptake during nasal and oral breathing, differences in uptake in an individual at two time points, and an examination of between-subject variability in O3 uptake. Exposure to O3 had no effect on the breathing parameters or gas exchange. Oral and nasal breathing frequency averaged 16.2 +/- 1.1 (SE) and 16.0 +/- 1.2 breaths per minute with tidal volumes averaging 651 +/- 46 and 669 +/- 67 ml, respectively. A significant correlation (p < 0.01) was found for the minute volume during resting breathing with the percentage of uptake. The percentage of O3 uptake was consistently higher (p = 0.02) during oral breathing (76.5% +/- 3.3) than during nasal breathing (73.1% +/- 3.0) although this difference may not be biologically significant. The variability in percentage of uptake between subjects was substantial with calculated uptakes ranging from 51 to 96%, a difference of about 45%. Variability in percentage of uptake for an individual was less with the maximal difference between the first and second visits being about 20%; the average difference, however, was only about 3%. We conclude that total percentage of O3 uptake is approximately 75% in adult males during resting breathing. It is slightly greater during oral than during nasal breathing, will vary considerably among subjects, and is moderately reproducible within a subject.

Administration, Inhalation↗
PubMed1996

High-resolution dosimetry using radiochromic film and a document scanner.

A method of reading exposed radiochromic film is described which has significant advantages over conventional densitometry. The method employs a document scanner and associated software for imaging the film. The resulting images are easily analysed using standard software to yield high-resolution dose maps. A calibration was performed which relates scanner signal to dose, allowing for the determination of dose at any point on an exposed film. Results obtained using a broad-band densitometer are compared to those where the scanner has been used. The technique was used to measure the dose distribution around a COMS-type ophthalmic applicator.

Densitometry↗
PubMed1995

Restrictive lung disease in rats exposed chronically to an urban profile of ozone.

The potential for irreversible lung impairment resulting from life-long ozone (O3) exposure remains uncertain. To address this question, young adult rats (male, F-344) were exposed to a simulated urban profile of O3 for 1, 3, 13, 52, or 78 wk, after which pulmonary function tests were performed. To assess reversibility of effects, cohorts from the 13-, 52-, and 78-wk groups were evaluated, respectively, after an additional 6, 27, and 17 wk of clean air. Static and dynamic lung properties were based on measurements of lung volume apportionment, respiratory system compliance (Crs), DLCO, multibreath N2 washout, and maximum expiratory flow-volume relationships. Electrocardiography was also performed in unanesthetized, restrained rats after 52 and 78 wk, as were determinations of wet and dry lung weights, lung collagen, and associated connective tissue crosslinks. Small (< 10%) but significant reductions in TLC and RV were noted after 13, 52, and 78 wk of O3 exposure. At 13 and 52 wk, N2 washout was enhanced, though at 78 wk it was similar to control. None of these changes appeared progressive with continued O3 exposure. Post exposure to clean air did not completely reverse the reduction in TLC. Additionally, Crs, though not affected during O3 exposure, decreased during the air recovery. No O3-related changes in collagen were apparent, however. Thus, near life-long exposure of F-344 rats to a worse-case, urban profile of O3 appears to have led to a functionally restrictive, i.e. "stiffened," lung without overt fibrosis. Furthermore, certain aspects of the O3-induced effect were not fully reversible.

Air Pollutants↗
PubMed1994

Sports fractures.

Fractures occur in athletes and dramatically influence performance during competitive and recreational activities. Fractures occur in athletes as the result of repetitive stress, acute sports-related trauma and trauma outside of athletics. The literature provides general guidelines for treatment as well as a variety of statistics on the epidemiology of fractures by sport and level of participation. Athletes are healthy and motivated patients, and have high expectations regarding their level of function. These qualities make them good surgical candidates. Although closed treatment methods are appropriate for most sports fractures, an aggressive approach to more complicated fractures employing current techniques may optimize their subsequent performance.

Adolescent↗
PubMed1993

Near-lifetime exposure of the rat to a simulated urban profile of nitrogen dioxide: pulmonary function evaluation.

To investigate the potential for up to a near-lifetime exposure to high-ambient levels of nitrogen dioxide (NO2) to induce functional lung damage, groups of rats were exposed to air or a simulated urban profile of NO2 (0.5 ppm background, 1.5 ppm peak) for 1, 3, 13, 52, or 78 weeks. The dynamic, static, and diffusional characteristics of the lung were evaluated postexposure in anesthetized rats. Furthermore, for the 13-, 52-, and 78-week groups, additional animals were tested after a 6-, 26-, or 17-week period in filtered air, respectively. No significant NO2 differences between exposed and control animals were found for the nitrogen washout, compliance, lung volume, or diffusion capacity of carbon monoxide measurements. At 78 weeks, however, a reduction in delta FEF25%, an estimate of convexity in the later portion of the forced expiratory flow volume curve, was observed. Breathing patterns and mechanisms were also assessed postexposure in a parallel group of similarly exposed unanesthetized rats. These rats were examined during a filtered air, 4 and 8% carbon dioxide (CO2) challenge. In the unanesthetized rat, frequency of breathing was significantly decreased and tidal volume, expiratory resistance, and inspiratory and expiratory times tended to increase. For several of these variables, the largest response also occurred at 78 weeks and seemed to be exacerbated by CO2 challenge.(ABSTRACT TRUNCATED AT 250 WORDS)

Air Pollutants↗
PubMed1992

7p deletion syndrome: an adult with mild manifestations.

Deletion of 7p results in a wide spectrum of congenital abnormalities and minor facial and hand anomalies, often including craniosynostosis. We report on the oldest recognized patient with this disorder, a 24-year-old woman with an interstitial deletion from p15.3-p21.2 or p21.3. The manifestations in this patient are milder than those of previously described patients, and include borderline mental retardation, short stature, minor facial anomalies, and several skeletal changes. The absence of craniosynostosis in this patient is noteworthy, given previous suggestions that there is a specific locus for this finding in the 7p region. Twelve cases of 7p deletion, in which the missing segment overlaps that of the current case, are reviewed. This case delineates a broader spectrum for patients with 7p deletion syndrome.

Abnormalities, Multiple↗
PubMed1992

Vitamin E effects on in vitro immunoglobulin M and interleukin-1 beta production and transcription in dairy cattle.

Experiments were conducted to determine the effect of dietary vitamin E on in vitro IgM and interleukin-1 production and its transcription by bovine peripheral blood mononuclear cells. Cells were isolated from Jersey cows and cultured with pokeweed mitogen, a T-cell-dependent, B-lymphocyte mitogen, to stimulate polyclonal IgM production. Addition of 55 and 110 ng/ml of alpha-tocopherol at time 0 to cell cultures containing pokeweed mitogen significantly enhanced IgM production compared with control cultures containing pokeweed mitogen alone. Cultures supplemented with 55 ng/ml of alpha-tocopherol at 0, 24, or 48 h after incubation with mitogen had enhanced IgM production compared with control cultures incubated for the same duration. However, addition of alpha-tocopherol to cultures at 72 and 96 h did not affect IgM production. Production of interleukin-1 in culture supernatants obtained 24 h after stimulation with pokeweed mitogen was similar between control cultures and cultures supplemented with alpha-tocopherol. At 48 h, secretion of interleukin-1 was maintained in the supplemented cultures but declined in control cultures. Mononuclear cells obtained from steers receiving vitamin E supplement or control steers were used to examine the effects of in vivo vitamin E status on interleukin-1 mRNA expression. Concanavalin A-stimulated cells from Jersey steers fed diets supplemented with vitamin E expressed 55% higher interleukin-1 mRNA than cells from control steers.

Animals↗
PubMed1990

Pulmonary effects due to subchronic exposure to oil fog.

Male and in some cases female rats were exposed to an oil fog generated by flash vaporization and subsequent condensation of light-weight lubricating oil. Exposures were for 3.5 h/d, 4d/wk for 13 wk. Males were exposed at concentrations of 1.5, 0.5, 0.2 or 0.0 mg/l (1500, 500, 200, and 0 mg/m3) and a particle size of approximately 1 micron (mass median aerodynamic diameter). A number of biologic endpoints were assessed the day after the last exposure and, in some cases, after a 4 wk recovery period. Effects of 1.5 mg/l on male and female rats were compared. Diffuse accumulation of macrophages in the alveoli was observed in all oil fog exposed groups. The degree of severity was concentration dependent. Histopathologic changes were more prominent in males than in females and represented the most notable gender-related differences. Histologic effects observed one day and 4 wk post exposure were similar. Minimal histopathologic changes and minimal increase in lavage fluid protein were the only effects observed at the 0.2 mg/l exposure level. There was a significant increase in lavage fluid protein, percent lavagable polymorphonuclear leukocytes and lung wet and dry weight following exposure to both 0.5 and 1.5 mg/l. At the highest exposure concentration effects on lung weights were still evident 4 wk post exposure. Pulmonary function endpoints including total lung capacity, vital capacity, residual volume, diffusing capacity to CO, compliance, and end expiratory volume (EEV) were unaffected by oil fog exposure with the exception of EEV in males exposed at the 1.5 mg/l level. All of the changes observed following oil fog exposure were consistent with a mild inflammatory edema.

Aerosols↗
PubMed1989

Does sunlight cause premature aging of the crystalline lens?

Premature onset of presbyopia may be an early sign of cataractous lenticular changes. For many years ultraviolet radiation (UVR) has been suspected as a major factor in the degradation of the crystalline lens. Controlled laboratory studies have demonstrated that UVR does cause opacities that closely resemble those naturally occurring in the aging process. Is it true that environmental UVR is also the prime contributor in the deleterious lenticular changes that may begin with premature presbyopia, as has been postulated? This review examines the evidence supporting this and other suggested causes of early presbyopia, including genetics, nutrition, toxins, and environmental temperature. Of all factors reported to affect the onset of presbyopia, UVR has the most scientific support, but further research is necessary to conclusively establish this link.

Aging↗