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Biomedical subjects

D Currie

Publications and source records attributed to D Currie.

At least 37 records · Page 2Linked to original sources
PubMed1991

Dynamic demonstration of proximal vergence and proximal accommodation.

The complex interactions between accommodation and vergence have been described by dual interactive models which include influences of convergence accommodation and accommodative vergence. Using an SRI Eyetracker, we investigated changes in vergence and accommodation stimulated while looking through prisms or lenses, and while looking at real targets located at different distances. Our results suggest that both proximal accommodation and proximal vergence are stimulated when looking from a distant to a near real target. We suggest that models of convergence and accommodation interactions include proximal accommodation and proximal vergence before the crosslinks.

Accommodation, Ocular↗
PubMed1991

Central effects of the calcium antagonist, nifedipine.

1. Central effects of the calcium antagonist, nifedipine retard (10, 20 and 40 mg) and nifedipine capsules (10 mg) were studied in 14 healthy male subjects. Two placebos and an active control drug, oxazepam (15 mg), were included. Medication was administered double-blind at 10.00 h. The effects of drugs on performance and subjective feelings were assessed before and from 1.5-2.5 h and 3.5-4.5 h after ingestion, and recordings of the electrical activity of the brain (EEG) and body sway carried out. 2. Performance was assessed using digit symbol substitution, continuous attention, letter cancellation, choice reaction time, finger tapping, immediate and short-term memory, together with critical flicker fusion and two flash fusion. The EEG was recorded with eyes open while the subjects carried out a mental arithmetic task, and with eyes closed, when they were required to relax. Body sway was recorded with eyes open and with eyes closed. Subjects assessed their mood and well-being on a series of 12 visual analogue scales. 3. Nifedipine did not alter performance levels on any of the skills tested, while oxazepam (15 mg) increased the number of errors (P less than 0.01) and reduced accuracy at continuous attention (P less than 0.01). 4. Nifedipine (10 mg) reduced total power of the EEG in the frequency range (0.5-30 Hz), and nifedipine (20 mg) increased total alpha power (7.5-13 Hz) (P less than 0.05). Oxazepam reduced alpha and increased beta 1 power (13.5-21 Hz).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Convergence accommodation: laboratory and clinical evaluation.

The accommodation stimulated by convergence, CA/C, was measured under laboratory and clinical conditions. There was a small nonlinearity to the CA/C ratios measured under laboratory conditions for three of six subjects. We found that convergence accommodation decreases with decreasing accommodative amplitude but not as rapidly as has been reported in the literature. Our results suggest that convergence accommodation can contribute substantially to the near accommodative response for many patients.

Accommodation, Ocular↗
PubMed1990

Central effects of the angiotensin-converting enzyme inhibitor, captopril. I. Performance and subjective assessments of mood.

1. Central effects of single doses of captopril (12.5, 25 and 50 mg) were studied in fourteen healthy male subjects. Two placebos and an active control drug, oxazepam (15 mg), were included, together with a single dose of atenolol (100 mg). The drugs were administered double-blind at 11.00 h, and performance and subjective feelings were assessed before and from 1.5-2.5 h and 3.5-4.5 h after ingestion. 2. Performance was assessed using digit symbol substitution, continuous attention, letter cancellation, choice reaction time, finger tapping, immediate and short-term memory, together with critical flicker fusion and two flash fusion. Subjects assessed their mood and well-being on a series of 12 visual analogue scales. 3. Captopril did not impair performance on any of the tests, but improved short-term memory (P less than 0.05) and increased the number of letters cancelled (P less than 0.05). Oxazepam reduced the number of substitutions completed in the digit symbol test (P less than 0.01), accuracy on continuous attention (P less than 0.05), number of letters cancelled (P less than 0.05), and rate of finger tapping (P less than 0.05), and increased choice reaction time (P less than 0.001). Atenolol reduced the rate of finger tapping (P less than 0.05), but increased the number of letters cancelled (P less than 0.05). 4. No effects on mood or on subjective feelings were evident with captopril. Oxazepam reduced subjective alertness (P less than 0.05), and atenolol increased feelings of sleepiness (P less than 0.05). 5. Although these observations suggest that central effects may exist with captopril, no adverse consequences have been established on performance or on subjective assessment of mood. Captopril may, therefore, be an appropriate drug for hypertensive patients engaged in skilled activity.

Adult↗
PubMed1990

Central effects of the angiotensin-converting enzyme inhibitor, captopril. II. Electroencephalogram and body sway.

1. Effects of single doses of captopril (12.5, 25 and 50 mg) on the electroencephalogram (EEG) and on body sway were studied in fourteen healthy male subjects. Oxazepam (15 mg), as an active control, and two placebos were included in the study, together with a single dose of atenolol (100 mg). Medication was administered double-blind at 11.00 h, and assessments made before and at 2 and 4 h after drug ingestion. 2. There were no changes in the EEG with captopril. Oxazepam reduced the circadian rise in alpha activity, while atenolol decreased beta power. Delta activity was modified by both oxazepam and atenolol. 3. A reduction in lower frequencies of body sway (0.05-1 Hz) occurred with captopril, while the spectra were unaffected by oxazepam. Atenolol increased (P less than 0.05) activity in the frequency range 0.75-2.75 Hz. 4. These observations suggest that captopril is free of central effects such as sedation that may occur with beta-adrenoceptor antagonists. Reduced body sway with captopril could reflect improved integration of central and peripheral control of posture.

Atenolol↗
PubMed1990

Nasal potential difference: a clinical diagnostic test for cystic fibrosis.

Patients with cystic fibrosis (CF) demonstrate a markedly more negative potential difference (PD) across respiratory epithelia than normal or "diseased" controls. A technique is described for the measurement of nasal PD in both children and adults. 145 non-CF subjects showed a mean PD of -19.0 mV (range -2 to -36) in comparison to 60 patients with cystic fibrosis with mean of -46.0 mV (range -32 to -77). Amongst the latter group those with more severe disease had a more negative PD. Measurement of nasal PD is easily learnt and rapidly performed and may provide an additional means of diagnosis for CF.

Adolescent↗
PubMed1989

Activation of the K-ras oncogene in liver tumors of Hudson River tomcod.

Adult Atlantic tomcod collected from the Hudson River slightly north of New York City have an extremely high incidence (55-90%) of histologically defined hepatocellular carcinomas, whereas tomcod from control sites in Maine or Rhode Island exhibit little evidence of this condition. Genomic DNA was isolated from Hudson tomcod tumors and from normal Hudson and Saco River, Maine tomcod livers and tested for transforming activity in the NIH3T3 transfection assay. Six out of nine tumors (66%) tested proved positive. Southern blot analysis of all primary (6/6) transfectant and nude mouse tumor DNAs revealed evidence of an exogenous tomcod K-ras gene, while no activation of the H-ras gene was observed. These studies demonstrate that an outbred population of fishes and inbred mammals suffer genetic alternations at the same oncogene loci and suggest that similar pathways to neoplasia may be operative in both systems. Oncogene activation in naturally exposed feral populations may prove a particularly sensitive marker of environmental degradation in aquatic systems.

Animals↗
PubMed1988

The effect of inhaled sulfur dioxide and systemic sulfite on the induction of lung carcinoma in rats by benzo[a]pyrene.

In a previous study at this Institute, inhaled sulfur dioxide (SO2) was shown to enhance the induction by inhaled benzo[a]pyrene (BaP) of squamous cell carcinoma (SQCA) of the respiratory tract of rats (S. Laskin, M. Kuschner, A. Sellakumar, and G. V. Katz, 1976, In "Air Pollution and the Lung," pp. 190-213). We attempted to confirm and extend this finding by using an experimental protocol intended to illuminate the role of SO2. Rats were treated with BaP by 15 consecutive weekly intratracheal instillations. Some of these rats were simultaneously exposed either to SO2 by inhalation or to sulfite/bisulfite anions that accumulated systemically from endogenous generation in rats with induced sulfite oxidase deficiency. The total treatment period spanned 21 weeks, after which the rats were observed for the development of tumors. BaP-treated rats began to die with SQCA of the respiratory tract at approximately 200 days after the first BaP treatment and at 2 years after the first treatment nearly all rats in the BaP-treated groups had died, most with SQCA. Survival in the control groups was excellent and the health of all groups (aside from pulmonary SQCA in BaP-treated groups) was also excellent. The probability of dying with a pulmonary SQCA in the experimental groups treated with BaP, BaP plus inhaled SO2, and BaP plus systemic sulfite/bisulfite was calculated by the logrank analysis. The data sets of SQCA probability from these groups were not statistically different (i.e., P greater than 0.05) by the chi 2 test indicating that, in this experiment, neither inhalation exposure to SO2 nor systemic exposure to sulfite/bisulfite anions affected the induction of SQCA of the lung by intratracheally instilled BaP. We conclude that the results of this study do not support an etiological role for either SO2 or sulfite/bisulfite anions in the induction of SQCA of the respiratory tract by BaP.

Administration, Inhalation↗
PubMed1988

Central effects of beta-adrenoceptor antagonists. I--Performance and subjective assessments of mood.

1. Central effects of the beta-adrenoceptor antagonists, propranolol (40, 80 and 160 mg) and atenolol (50 and 100 mg) were studied in 12 healthy male subjects. Two placebo ingestions and an active control (oxazepam 15 mg) were included. Single doses were administered double-blind at 11.00 h, and assessments of performance and subjective feelings were made before, 2 h and 4 h after ingestion. 2. Performance was measured using letter cancellation, digit symbol substitution, continuous attention, choice reaction time, finger tapping, short term and immediate memory, critical flicker fusion and two flash fusion. Subjective feelings were assessed using twelve visual-analogue scales. 3. Oxazepam impaired performance at letter cancellation (P less than 0.001), digit symbol substitution (P less than 0.05), continuous attention (P less than 0.001), immediate recall (P less than 0.05) and finger tapping (P less than 0.05), but neither of the beta-adrenoceptor antagonists affected these measures. Propranolol (40 and 160 mg) also impaired short term memory (P less than 0.05), though it was not possible to establish this effect with atenolol. 4. Subjective alertness was reduced by oxazepam (P less than 0.01) and atenolol (P less than 0.05), while propranolol (40 mg) reduced anxiety (P less than 0.01) and propranolol (80 mg) impaired ability to concentrate (P less than 0.05). 5. The results suggest that both lipophilic and hydrophilic antagonists modify the central nervous system, though impairment may be difficult to establish with conventional tests. The observations on memory and alertness suggest that the central effect of beta-adrenoceptor antagonists may be subtle.

Adrenergic beta-Antagonists↗
PubMed1988

Central effects of beta-adrenoceptor antagonists. II--Electroencephalogram and body sway.

1. Effects of the beta-adrenoceptor antagonists, propranolol (40, 80 and 160 mg) and atenolol (50 and 100 mg) on the electroencephalogram and on body sway, were studied in 12 healthy male subjects. The study was double-blind, and included two placebos and an active control, oxazepam (15 mg). Medication was ingested at 11.00 h, and assessments were made before, and at 2 h and 4 h after ingestion. 2. All doses of both beta-adrenoceptor antagonists modified the electroencephalogram, and the changes reported were statistically significant at probability levels of less than 5%. The circadian rise in alpha activity was reduced by both beta-adrenoceptor antagonists as well as by oxazepam. Atenolol also decreased beta activity. 3. Body sway was modified by atenolol and oxazepam (P less than 0.05). The increase with oxazepam was most marked in the low frequency component (0.05-2.25 Hz) of the spectrum, while atenolol modified only the component of higher frequency (2.25-4.0 Hz). 4. These observations suggest that propranolol and atenolol have a sedative effect, and that hydrophilic antagonists are unlikely to be free of central activity. The changes in body sway could imply that peripheral mechanisms may be modified at least with atenolol.

Adrenergic beta-Antagonists↗
PubMed1988

Zygomaticotemporal approach to the basis cranii and basilar artery.

When using the zygomaticotemporal approach, one removes the whole of the zygomatic bone with its attachment to the masseter muscle, allowing a lower and more anterior approach to the interpeduncular cistern along the inferomedial surface of the temporal lobe. Minimal brain retraction is required to give an excellent view of the bifurcation of the basilar artery and of the suprasellar region.

Basilar Artery↗
PubMed1987

Establishment of a rat nasal epithelial tumor cell line.

A new cell line designated NAS 2BL has been established from a rat nasal tumor induced by inhalation of the direct-acting carcinogen methylmethane sulfonate. The cells are epithelial in morphology, have a generation time of 34 h, require 10% fetal bovine serum for optimal growth, and exhibit keratinization at confluence. The karyotype is aneuploid, with several marker chromosomes, and the cells are transformed by the criterion of nude mouse tumorigenicity.

Animals↗
PubMed1987

Distribution, metabolism and toxicity of inhaled sulfur dioxide and endogenously generated sulfite in the respiratory tract of normal and sulfite oxidase-deficient rats.

We report on the distribution, metabolism, and toxicity of sulfite in the respiratory tract and other tissues of rats exposed to endogenously generated sulfite or to inhaled sulfur dioxide (SO2). Graded sulfite oxidase deficiency was induced in several groups of rats by manipulating their tungsten to molybdenum intake ratio. Endogenously generated sulfite and S-sulfonate compounds (a class of sulfite metabolite) accumulated in the respiratory tract tissues and in the plasma of these rats in inverse proportion to hepatic sulfite oxidase activity. In contrast to this systemic mode of exposure, sulfite exposure of normal, sulfite oxidase-competent rats via inhaled SO2 (10 and 30 ppm) was restricted to the airways. Minor pathological changes consisting of epithelial hyperplasia, mucoid degeneration, and desquamation of epithelium were observed only in the tracheas and bronchi of the rats inhaling SO2, even though the concentration of sulfite plus S-sulfonates in the tracheas and bronchi of these rats was considerably lower than that in the endogenously exposed rats. We attribute this histological damage to hydrogen ions stemming from inhaled SO2, not to the sulfite/bisulfite ions that are also a product of inhaled SO2. In addition to the lungs and trachea, all other tissues examined, except the testes, appeared to be refractory to high concentrations of endogenously generated sulfite. The testes of grossly sulfite oxidase-deficient rats were severely atrophied and devoid of spermatogenic cells.

Administration, Inhalation↗
PubMed1986

Beat frequency of cilia from sites of purulent infection.

Mucociliary clearance depends on the interaction between cilia and mucus; it is delayed in the presence of purulent secretions. Nasal mucociliary clearance was examined by the saccharin method and nasal ciliary beat frequency by a photometric technique. Four groups were studied: normal controls, patients with bronchiectasis without nasal symptoms, patients with chronic mucopurulent sinusitis alone, and patients with chronic mucopurulent sinusitis and bronchiectasis. Nasal mucociliary clearance was prolonged in infected patients. Cilia obtained from the site of purulent secretions were found to beat more slowly in vitro (mucopurulent sinusitis 12.1 Hz, mucopurulent sinusitis and bronchiectasis 11.6 Hz), than those obtained from normal controls (14.3 Hz) and from patients with bronchiectasis alone (13.6 Hz). The cause of the ciliary slowing seemed most likely to be the release of host factors during the inflammatory response, rather than the particular organism isolated. Ciliary slowing may contribute to the observed delay of mucociliary clearance in conditions in which purulent secretions are present.

Adolescent↗
PubMed1984

Colonic carcinoma associated with an abnormal collagen table. Collagenous colitis.

A case of cecal adenocarcinoma with the typical histopathologic features of collagenous colitis throughout the resected colon is described in a 67-year-old woman. Collagenous colitis has not previously been reported in association with adenocarcinoma of the colon and the relationship of these findings appears to be unprecedented. A review of 100 randomly selected Duke's B adenocarcinomas of the colon revealed no similar case.

Adenocarcinoma↗