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Biomedical subjects

H E Evans

Publications and source records attributed to H E Evans.

At least 19 recordsLinked to original sources
PubMed2006

Uptake and elimination of lead, zinc, and copper by caddisfly larvae (Trichoptera: Hydropsychidae) using stable isotope tracers.

Stable isotopes of Pb, Zn, and Cu were used in laboratory experiments to determine the uptake and elimination of these metals by stream-dwelling caddisfly (Trichoptera: Hydropsychidae) larvae. For Pb and Cu, larvae were exposed to environmentally realistic levels (2.5 and 4.5 microg x L(-1), respectively) of one isotope for 9 days followed by a 9-day exposure to either the same isotope, to a second stable isotope of the same metal, or to RW containing no added isotope (two phases in total). For zinc, the exposure concentration was 15 microg x L(-1), and the experiment lasted for a total of 27 (i.e., three phases) rather than 18 days to see if uptake and elimination changed during the extended time period. The uptake clearances (k(u)) determined for the various metals averaged 7.8, 1.4, and 0.6 L x g dw(-1) x d(-1) for Pb, Zn, and Cu, respectively, if the total metal concentration in the water was used in the calculations. The clearance rate constants (k(e)) were less variable, averaging 0.15 d(-1) for Pb, 0.22 d(-1) for Zn, and approximately 0.1 d(-1) for Cu and were similar in both the presence (i.e., elimination) and absence (i.e., depuration) of metal in the water. These values are also comparable with those reported in the literature for other aquatic invertebrates. The use of stable isotopes thus allowed simultaneous measurement of uptake and clearance (elimination and depuration) of these metals at environmentally realistic concentrations and could be of great benefit for determining partitioning, assimilation efficiency, and pathways of these and other metals in the environment.

Animals↗
PubMed2001

Comparison of iron accumulation in lakes using sediment core and mass balance calculations.

The accumulation of iron (Fe) in several lakes in Ontario, Canada was determined by two independent approaches. First, Fe accumulation was calculated in cores collected from several sites in each lake by integrating Fe concentration profiles with sediment accumulation rates determined from Pb210 dating. These site-specific accumulation rates were corrected for sediment focussing so that whole-lake Fe accumulation values could be derived. Using this approach, recent whole-lake Fe accumulation in eight lakes ranged between approximately 750 and 4000 mg/m2 per year. Second, whole-lake Fe accumulation was estimated from lake mass budgets, which were measured over a maximum of 14 years. Accumulation measured using the mass balances ranged from 10 to 1330 mg/m2 per year. Comparison of the two approaches indicated that retentions calculated from the sediment cores were much greater than those estimated from the mass balances. The most likely explanation for this difference is that, in the two decades since the cores were collected, there has been a substantial decline in Fe retention (in mass units but not percent) in the study lakes, principally as a result of reduced inputs of Fe from the catchments.

Journal Article↗
PubMed1999

Implications for space radiation environment models from CREAM & CREDO measurements over half a solar cycle.

Flight data obtained between 1990 and 1997 from the Cosmic Radiation Environment Monitors CREAM & CREDO carried on UoSAT-3, Space Shuttle, STRV-1a (Space Technology Research Vehicle) and APEX (Advanced Photovoltaic and Electronics Experiment Spacecraft) provide coverage over half a solar cycle. The modulation of cosmic rays and evolution of the South Atlantic Anomaly are observed, the former comprising a factor of three increase at high latitudes and the latter a general increase accompanied by a north-westward drift. Comparison of particle fluxes and linear energy transfer (LET) spectra is made with improved environment & radiation transport calculations which account for shield distributions and secondary particles. While there is an encouraging convergence between predictions and observations, significant improvements are still required, particularly in the treatment of locally produced secondary particles. Solar-particle events during this time period have LET spectra significantly below the October 1989 event which has been proposed as a worst case model.

Atlantic Ocean↗
PubMed1998

Observations and predictions of secondary neutrons on Space Shuttle and aircraft.

The Cosmic Radiation Effects and Activation Monitor has flown on six Shuttle flights between September 1991 and February 1995 covering the full range of inclinations as well as altitudes between 220 and 570 km, while a version has flown at supersonic altitudes on Concorde between 1988 and 1992 and at subsonic altitudes on a SAS Boeing 767 between May and August 1993. The Shuttle flights have included passive packages in addition to the active cosmic ray monitor which comprises an array of pin diodes. These are positioned at a number of locations to investigate the influence of shielding and local materials. Use of both metal activation foils and scintillator crystals enables neutron fluences to be inferred from the induced radioactivity which is observed on return to Earth. Supporting radiation transport calculations are performed to predict secondary neutron spectra and the energy deposition due to nuclear reactions in silicon pin diodes and the induced radioactivity in the various scintillator crystals. The wide variety of orbital and atmospheric locations enables investigation of the influence of shielding on cosmic ray, trapped proton and solar flare proton spectra.

Aircraft↗
PubMed1998

Updated measurements from CREAM & CREDO & implications for environment & shielding models.

Flight data obtained between 1995 and 1997 from the Cosmic Radiation Environment Monitors CREAM & CREDO carried on UoSat-3, Space Shuttle, STRV-1a (Space Technology Research Vehicle) and APEX (Advanced Photovoltaic and Electronics Experiment Spacecraft) have been added to the dataset affording coverage since 1990. The modulation of cosmic rays and evolution of the South Atlantic Anomaly are observed, the former comprising a factor three increase at high latitudes and the latter a general increase accompanied by a westward drift. Comparison of particle fluxes and linear energy transfer spectra is made with improved environment & radiation transport calculations which account for shield distributions and secondary particles. While there is an encouraging convergence between predictions and observations, significant improvements are still required, particularly in the treatrnent of locally produced secondary particles.

Atlantic Ocean↗
PubMed1994

Congenital syphilis.

Congenital syphilis offers many parallels with perinatal HIV infection. Both affect multiple organs including the central nervous system, may be asymptomatic for months to years, and pose diagnostic dilemmas, especially from a laboratory perspective. Syphilis is a co-infection in some cases of HIV. Public policy issues raised by the AIDS epidemic, including stigmatization, discrimination, and denial of access to health care, have their antecedents in syphilis.

Anti-Bacterial Agents↗
PubMed1994

Public policy and AIDS.

In summary of some of the major issues raised by AIDS (Table 1), social, political, and economic forces all impact on the global outbreak of AIDS. Conversely the epidemiologic and medical realities of this disease have forced a reconsideration of moral and ethical values, prioritization of resource allocation, and pervasion of virtually every aspect of the health care delivery system. Advocates for AIDS funding have set a model for other espousing the significance of diseases ranging from rare disorders to breast cancer. As this issue was written (summer 1993), it was apparent that attention of the media had shifted to numerous other domestic and foreign concerns. Hopefully, when the Clinics next present perinatal AIDS, the pendulum will have swung back and there will be a wider variety of effective therapeutic agents available permitting longer survival of greater quality.

AIDS Serodiagnosis↗
PubMed1990

The effect of 60% oxygen on air-space enlargement and cross-linked elastin synthesis in hamsters with elastase-induced emphysema.

Hyperoxia is routinely administered to patients with severe emphysema. To gain insight into the possibly adverse effects of such treatment, hamsters were exposed to 60% oxygen for 5 days, beginning 48 h after induction of pulmonary emphysema by intratracheal instillment of pancreatic elastase. Control groups consisted of (1) animals instilled with elastase and exposed to room air, (2) animals instilled with saline and exposed to 60% oxygen, and (3) animals instilled with saline and exposed to room air. Cross-linked elastin content and synthesis in the lung were measured immediately following termination of hyperoxia, and the mean linear intercept was determined 4 wk later. Cytologic examination of bronchoalveolar lavage fluids was also performed. Statistical significance was determined by a two-way analysis of variance. Results indicate that exposure to 60% oxygen significantly affected (p less than 0.05) air-space size, causing a 51% increase among elastase-treated hamsters (124 versus 82 microns) but only a 4% increment among saline-treated animals (52 versus 50 microns). When compared to other groups, animals treated with both elastase and hyperoxia had a significantly greater (p less than 0.01) percentage of neutrophils (28%) in their lung lavage fluids immediately following exposure to 60% oxygen. Although total lung elastin content was not altered by hyperoxia at this time, labelling of elastin cross-links was significantly increased (p less than 0.05). These studies demonstrate that exposure to 60% oxygen enhances elastase-induced lung injury. They also raise the possibility that oxygen therapy may, under certain circumstances, accelerate the progression of human emphysema.

Animals↗
PubMed1990

Improvement of neutrophil migration by systemic vitamin C in neonates.

The effect of oral vitamin C on chemotactic and random migration of neutrophils in 20 neonates (10 normal and 10 with suspected sepsis) was evaluated. Chemotaxis and random migration were studied between 24 and 48 hours of life, before and 24 hours after the administration of 400 mg (divided in four doses) of vitamin C. Chemotactic migration improved by 65% and random migration by 57% following vitamin C administration. The significant improvement in chemotaxis (P less than .01) and random migration may justify the inclusion of vitamin C as an adjunct to the therapy of neonatal sepsis.

Ascorbic Acid↗
PubMed1988

Morphology and embryological interpretation of a congenital occipito-atlanto-axial malformation in a dog.

A clinical, radiological, and morphological study of a congenital occipito-atlanto-axial malformation in a 13-week-old male Saint Bernard dog that became suddenly tetraplegic at 8 weeks is described. The dog was recumbent, had generalized muscle atrophy, but was alert and responsive. Pain was elicited when the head-neck junction and the cervical vertebrae were palpated, and a bony abnormality was palpated at the occiput and atlas. Clinical signs of upper motor neuron and general proprioceptive deficits in all four limbs were compatible with a focal lesion in the cervical spinal cord. Plain radiographs of the head and neck revealed malformation of the occipital bones, atlas, and axis, unilateral atlanto-occipital fusion, and atlanto-axial subluxation. At necropsy the right half of the atlantal neural arch was fused to the right exoccipital bone. On the axis, the dens was small, malformed, and deviated to the left; the transverse processes were enlarged; and the spinous process was small with a cleft caudally. The spinal cord was severely compressed at the level of the atlanto-axial articulation, and histological examination revealed extensive loss of neuronal cell bodies, axons, myelin, and the central canal. Reactive astrogliosis was also extensive. After a discussion of normal and abnormal development of the vertebral column and its joints, it was concluded that a failure of normal joint development at about 30 days of gestation in the dog could lead to congenital occipito-atlanto-axial malformation.

Animals↗
PubMed1987

Aerosol inhalation teaching device.

To facilitate teaching of inhalation technique to children, we have developed an aerosol inhalation teaching device by modifying the jacket of a canister nebulizer so that inhalation is accompanied by a horn sound and a flashlight is turned on when the canister is actuated. The device was evaluated in 33 children with asthma who had either never used a canister nebulizer (13 patients) or used incorrect technique (20 patients). The inhalation technique was first taught with conventionally, that is, verbal directions and demonstration with a canister nebulizer for 10 minutes. Only 10 (30%) of 33 children learned the technique. The remaining 23 were then taught with the special device. Twenty of 23 learned the technique within 10 minutes, but three others took longer. In a second study, 22 children, 11 of whom were beginners and 11 incorrect users, were instructed with the teaching device from the beginning. Seventeen (77%) learned the technique within 10 minutes; five others took longer. Most children can be taught the aerosol inhalation technique with this easily constructed device.

Adolescent↗
PubMed1987

Single-dose gentamicin therapy of recurrent urinary tract infection in patients with normal urinary tracts.

Results of single-dose therapy of urinary tract infections in pediatric patients have been contradictory mainly because of selection criteria. We evaluated the efficacy of a single dose of gentamicin in patients with normal urinary tracts and in whom urinary tract infections were recurrent. Twenty-one patients were included in the study, and a similar number in a conventional group given treatment for 10 days. Cure rate was 100% in both groups. The recurrence rates of 67% in the study and 52% in the conventional group were comparable. Single-dose therapy seems to have a role in the treatment of urinary tract infection in the absence of urinary tract malformation.

Adolescent↗
PubMed1987

Role of neutrophil chemotaxis in the pathogenesis of urinary tract infection.

Status of neutrophil chemotaxis was evaluated in seventeen infants and children with acute urinary tract infection. Four different chemotactic factors including those generated by patient's own invading pathogens were studied against patient cells. Chemotactic migration was found to be depressed during active infection and gradually returned to normal after successful eradication of the organisms. During a second episode of UTI chemotaxis again became defective. Inhibition of neutrophil chemotaxis seems to be at least one mechanism in the pathogenesis of UTI. Counteracting the suppression may play a role in modifying the inflammatory process and/or enhancing recovery during therapy.

Adolescent↗
PubMed1987

Evaluation of inhalation aids of metered dose inhalers in asthmatic children.

Many patients have incorrect aerosol inhalation technique with metered dose inhalers (MDI). Several inhalation aids have been developed and marketed for these patients. Even those who have correct inhalation technique may benefit from these devices. We compared bronchodilator efficacy of two puffs of albuterol aerosol administered either directly from a MDI mouthpiece, or from an inhalation aid (InspirEase, Aerochamber, Aerosol Bag) in 20 children who had previously demonstrated proper inhalation technique. The children received two puffs of aerosol from a MDI in each of two modalities tested each day on four different days (double blind). One modality contained albuterol aerosol and the other placebo. Pulmonary function was tested before and at 15, 30, 60, 120, and 180 minutes after treatment. Forced expiratory volume in 1 second (FEV1) increased similarly after all four modes of administration. Six patients who had incorrect inhalation technique benefited from the three inhalation aids. The aerosol bag and InspirEase produced slightly greater bronchodilator response than the Aerochamber. The inhalation aids are useful devices for those who have incorrect inhalation technique, but those who have correct technique do not derive any benefit from these devices.

Adolescent↗
PubMed1986

Prenatal development of the composite occipito-atlanto-axial synovial joint cavity in the dog.

In the dog, the synovial cavities of the atlanto-occipital and atlanto-axial joints communicated to form a single large composite joint cavity. The prenatal development of this composite occipito-atlanto-axial joint cavity was studied by examining 26 serially sectioned dog embryos and fetuses that ranged in size from 19 to 68 mm crown-rump length, and were between 30 and 42 days of gestational age. In the composite occipito-atlanto-axial joint, trilaminar interzones developed at 19-22 mm (30-31 days), joint cavities opened at 27-32 mm (33-34 days), and the atlanto-occipital and atlanto-axial cavities first communicated at 48 mm (37 days).

Animals↗
PubMed1986

Defective neutrophil chemotaxis in patients with alpha-1-antitrypsin deficiency.

The PMNs of five infants and children with homozygous alpha-1-antitrypsin deficiency (PiZZ phenotype) revealed defective chemotactic migration, and their PiZZ sera generated a higher quantity of chemotactic factor(s). This defect(s) might have been responsible for the increased incidence of infections found in our deficient PiZZ patients. Further studies are needed to clarify the role of defective chemotaxis in the pathogenesis of chronic lung disease associated with the PiZZ state.

Chemotaxis, Leukocyte↗
PubMed1986

Oxidant-mediated lung disease in newborn infants.

High concentrations of oxygen are administered with increased airway pressure to most preterm neonates with respiratory distress syndrome (RDS). Among 20% to 30% of survivors a form of chronic lung disease, bronchopulmonary dysplasia (BPD), develops. Its pathogenesis may include tissue damage caused by the superoxide anion (O2-) and other free oxygen radicals. Animal experiments and other data suggested a rationale for superoxide dismutase (SOD) administration in an effort to prevent or ameliorate BPD. Our preliminary studies in 19 prematures with RDS demonstrated its safety in human newborns and permitted measurement of its plasma levels. No adverse clinical findings occurred, and laboratory parameters were unchanged. Subcutaneous administration (0.25 mg/kg) of bovine SOD led to detectable levels at 1 1/2 h (mean 0.22 microgram/ml), with a slight rise to a higher peak at 2 1/2-4 h and a plateau over the remainder of the 12-h interval. Following doses 2-5, peak levels of 0.64 microgram/ml occurred at 4-8 h. With this background, a prospective double-blind controlled study of 45 neonates (mean gestational age, 29 weeks; birth weight, 1,100 g) showed a statistically significant reduction in prevalence of clinical and X-ray signs of BPD with fewer days of continuous positive airway pressure required. The safety and pharmacokinetics of bovine SOD were confirmed.

Antioxidants↗