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Biomedical subjects

C Wall

Publications and source records attributed to C Wall.

At least 19 recordsLinked to original sources
PubMed1992

Canadian National Breast Screening Study: 1. Breast cancer detection and death rates among women aged 40 to 49 years.

OBJECTIVES: To evaluate the efficacy of the combination of annual screening with mammography, physical examination of the breasts and the teaching of breast self-examination in reducing the rate of death from breast cancer among women aged 40 to 49 years on entry. DESIGN: Individually randomized controlled trial. SETTING: Fifteen urban centres in Canada with expertise in the diagnosis and treatment of breast cancer. PARTICIPANTS: Women with no history of breast cancer and no mammography in the previous 12 months were randomly assigned to undergo either annual mammography and physical examination (MP group) or usual care after an initial physical examination (UC group). The 50,430 women enrolled from January 1980 through March 1985 were followed for a mean of 8.5 years. DATA COLLECTION: Derived from the participants by initial and annual self-administered questionnaires, from the screening examinations, from the patients' physicians, from the provincial cancer registries and by record linkage to the Canadian National Mortality Data Base. Expert panels evaluated histologic and death data. MAIN OUTCOME MEASURES: Rates of referral from screening, rates of detection of breast cancer from screening and from community care, nodal status, tumour size, and rates of death from all causes and from breast cancer. RESULTS: Over 90% of the women in each group attended the screening sessions or returned the annual questionnaires, or both, over years 2 to 5. The characteristics of the women in the two groups were similar. Compared with the Canadian population, the participants were more likely to be married, have fewer children, have more education, be in a professional occupation, smoke less and have been born in North America. The rate of screen-detected breast cancer on first examination was 3.89 per 1000 in the MP group and 2.46 per 1000 in the UC group; more node-positive tumours were found in the MP group than in the UC group. During years 2 through 5 the ratios of observed to expected cases of invasive breast cancer were 1.26 in the MP group and 1.02 in the UC group. Of the women with invasive breast cancer through to 7 years, 191 and 157 women in the MP and UC groups respectively had no node involvement, 55 and 43 had one to three nodes involved, 47 and 23 had four or more nodes involved, and 38 and 49 had an unknown nodal status. There were 38 deaths from breast cancer in the MP group and 28 in the UC group. The ratio of the proportions of death from breast cancer in the MP group compared with those in the UC group was 1.36 (95% confidence interval 0.84 to 2.21). The survival rates were similar in the two groups. The highest survival rate occurred among women whose cancer had been detected by mammography alone. CONCLUSION: The study was internally valid, and there was no evidence of randomization bias. Screening with yearly mammography and physical examination of the breasts detected considerably more node-negative, small tumours than usual care, but it had no impact on the rate of death from breast cancer up to 7 years' follow-up from entry.

Adult↗
PubMed1992

Canadian National Breast Screening Study: 2. Breast cancer detection and death rates among women aged 50 to 59 years.

OBJECTIVE: To evaluate the efficacy of annual mammography over and above annual physical examination of the breasts and the teaching of breast self-examination among women aged 50 to 59 on entry. DESIGN: Individually randomized controlled trial. SETTING: Fifteen urban centres in Canada with expertise in the diagnosis and treatment of breast cancer. PARTICIPANTS: Women with no history of breast cancer and no mammography in the previous 12 months were randomly assigned to undergo either annual mammography and physical examination (MP group) or annual physical examination only (PO group). The 39,405 women enrolled from January 1980 through March 1985 were followed for a mean of 8.3 years. DATA COLLECTION: Derived from the participants by initial and annual self-administered questionnaires, from the screening examinations, from the patients' physicians, from the provincial cancer registries and by record linkage to the Canadian National Mortality Data Base. Expert panels evaluated histologic and death data. MAIN OUTCOME MEASURES: Rates of referral from screening, rates of detection of breast cancer from screening and from community care, nodal status, tumour size and rates of death from all causes and from breast cancer. RESULTS: Over 85% of the women in each group attended the screening sessions after screen 1. The characteristics of the women in the two groups were similar. Compared with the Canadian population the participants were more likely to be married, have fewer children, have more education, be in a professional occupation, smoke less and have been born in North America. The rate of screen-detected breast cancer on first examination was 7.20 per 1000 in the MP group and 3.45 per 1000 in the PO group, more node-positive tumours were found in the MP group than in the PO group. At subsequent screens the detection rates were a little less than half the rates at screen 1. During years 2 through 5 the ratios of observed to expected cases of invasive breast cancer were 1.28 in the MP group and 1.18 in the PO group. Of the women with invasive breast cancer through to 7 years, 217 in the MP group and 184 in the PO group had no node involvement, 66 and 56 had one to three nodes involved, 32 and 34 had four or more nodes involved, and 55 and 46 had an unknown nodal status. There were 38 deaths from breast cancer in the MP group and 39 in the PO group. The ratio of the proportions of death from breast cancer in the MP group compared with those in the UC group was 0.97 (95% confidence interval 0.62 to 1.52). The survival rates were similar in the two groups. Women whose cancer had been detected by mammography alone had the highest survival rate. CONCLUSION: The study was internally valid, and there was no evidence of randomization bias. Screening with yearly mammography in addition to physical examination of the breasts detected considerably more node-negative, small tumours than screening with physical examination alone, but it had no impact on the rate of death from breast cancer up to 7 years' follow-up from entry.

Breast Neoplasms↗
PubMed1992

Plasticity of the human otolith-ocular reflex.

The eye movement response to earth vertical axis rotation in the dark, a semicircular canal stimulus, can be altered by prior exposure to combined visual-vestibular stimuli. Such plasticity of the vestibulo-ocular reflex has not been described for earth horizontal axis rotation, a dynamic otolith stimulus. Twenty normal human subjects underwent one of two types of adaptation paradigms designed either to attenuate or enhance the gain of the semicircular canal-ocular reflex prior to undergoing otolith-ocular reflex testing with horizontal axis rotation. The adaptation paradigm paired a 0.2 Hz sinusoidal rotation about a vertical axis with a 0.2 Hz optokinetic stripe pattern that was deliberately mismatched in peak velocity. Pre- and post-adaptation horizontal axis rotations were at 60 degrees/s in the dark and produced a modulation in the slow component velocity of nystagmus having a frequency of 0.17 Hz due to putative stimulation of the otolith organs. Results showed that the magnitude of this modulation component response was altered in a manner similar to the alteration in semicircular canal-ocular responses. These results suggest that physiologic alteration of the vestibulo-ocular reflex using deliberately mismatched visual and semicircular canal stimuli induces changes in both canal-ocular and otolith-ocular responses. We postulate, therefore, that central nervous system pathways responsible for controlling the gains of canal-ocular and otolith-ocular reflexes are shared.

Adaptation, Physiological↗
PubMed1992

System identification of perilymphatic fistula in an animal model.

An acute animal model has been developed in the chinchilla for the study of perilymphatic fistulas. Micropunctures were made in three sites to simulate bony, round window, and oval window fistulas. The eye movements in response to pressure applied to the external auditory canal were recorded after micropuncture induction and in preoperative controls. The main pressure stimulus was a pseudorandom binary sequence (PRBS) that rapidly changed between plus and minus 200 mm of water. The PRBS stimulus, with its wide frequency bandwidth, produced responses clearly above the preoperative baseline in 78 percent of the runs. The response was better between 0.5 and 3.3 Hz than it was below 0.5 Hz. The direction of horizontal eye movement was toward the side of the fistula with positive pressure applied in 92 percent of the runs. Vertical eye movements were also observed. The ratio of vertical eye displacement to horizontal eye displacement depended upon the site of the micropuncture induction. Thus, such a ratio measurement may be clinically useful in the noninvasive localization of perilymphatic fistulas in humans.

Acoustic Stimulation↗
PubMed1991

What should dentists prescribe?

In recent months in Australia the, country's Association has been negotiating with the Federal Government over the rights of dentists to prescribe. The question is not the legal right to order a drug for a patient, but the entitlement of patients to a Government health scheme benefit for the dentist's prescription. The debate has, however, opened up broader questions. What is a reasonable extent of entitlement? What should a dentist be allowed to prescribe?

Australia↗
PubMed1991

Governing the profession--us or them?

Most dentists are heartily sick of the George Bernard Shaw quotation 'The professions are a conspiracy against the laity.' It seems to be the first phrase that pops into the mind of a non-professional when the question of self-regulation in the professions is discussed. It makes no difference at all that the true professions--including dentistry--have as a fundamental ethos the priority of a client's interests over the self-interest of the professional. Perhaps the non-professional, in this day and age, is much too hooked on the Gordon Milken ethos 'Greed is good', and assumes that everyone is alike.

Australia↗
PubMed1991

Dysplasia and the natural history of cervical cancer: early results of the Toronto Cohort Study.

A sample of 176,808 Pap smears, taken from 70,236 women, was constructed from the records of a large cytopathology laboratory between 1962 and 1981. The prevalence of cervical dysplasia, based on the distribution of initial smear results, rose from 42.7 to 94.9 per 1000 during the study period. The relative risks (RR) for the manifestation of a malignancy (carcinoma in situ or worse) in a subsequent cervical smear were 1.48, 3.42, 20.9 and 71.5 for women with minimal, mild, moderate and severe dysplasia, respectively, compared with the entire cohort. The initial degree of dysplasia for women developing a malignancy was much more likely to be interpreted as moderate (RR = 5.0) or severe (RR = 42.3) than were those for controls. These results are strongly supportive of the hypothesis that the degree of dysplasia is related to the risk of development of cancer of the cervix.

Adult↗
PubMed1990

Women's attitudes to screening after participation in the National Breast Screening Study. A questionnaire survey.

A self-administered questionnaire study exploring women's attitudes to breast screening after participation in the Canadian National Breast Screening Study (NBSS) achieved an 82% response rate. Of active respondents (AR) attending two to five screening examinations, 1582 had received annual mammography (MA) and physical examination (PE) of the breasts and 548 received annual PE alone. Of 139 dropouts after the first screening, 105 received MA and PE and 34 received PE alone. Dropout respondents (DR) were significantly less likely than AR to report receiving very prompt (46% versus 66%), very courteous (73% versus 92%), or very competent examinations (74% versus 95%). Although 35% of those allocated to PE expressed disappointment with PE allocation compared with 9% of those allocated to MA, fewer of those allocated PE were prepared to accept MA in the future than those allocated MA (59% versus 73%). Of those who had MA, 36% reported moderate and 9% extreme discomfort from mammography. Almost half of each subgroup--MA allocations, PE allocations, and DR--preferred mammography every 2 to 3 years and 30% preferred mammography restricted to diagnostic purposes. Only 5% of AR reported anxiety after screening. National Breast Screening Study participation was a positive experience for 93%. An intention to do breast self-examination (BSE) was reported by 89% of AR and 79% of DR. Forgetfulness was a major impediment to BSE. Disincentives for screening were excessive distance to center, painful mammography, fear of radiation, lack of time, and preference for own physician. Convenient location, punctual appointments, and courteous and supportive staff should enhance screening compliance.

Adult↗
PubMed1990

Vestibular function in periodic alternating nystagmus.

The vestibulo-ocular reflex of 4 patients with periodic alternating nystagmus (PAN) was studied in detail. Rotational testing was used to investigate the horizontal semicircular canal-ocular reflex, canal-otolith interaction, and the dynamic otolith-ocular reflex. Results indicated abnormal gain and phase of the horizontal semicircular canal-ocular reflex during sinusoidal rotation and a variable rate of decay of postrotatory responses. Each patient had abnormal canal-otolith interaction. An enlarged modulation component of the dynamic otolith-ocular response was observed in each patient. This study supports the idea that PAN is caused by an instability in the velocity storage element, a hypothetical neural circuit that perseverates the eye movement response to both vestibular and optokinetic stimulation. Further, we postulate that PAN may be caused by lesions of the cerebellar uvula and nodulus or their connections with the brainstem vestibular nuclei.

Adult↗
PubMed1990

Canadian National Breast Screening Study: assessment of technical quality by external review.

Mammograms from the Canadian National Breast Screening Study (NBSS) were reviewed by three external experts to provide an objective evaluation of their technical quality, to establish a model for auditing mammograms in a screening program, and to assess whether NBSS mammograms improved over time. The sample reviewed included 10 randomly chosen mammograms from each of 15 screening centers for each calendar year of their operation between 1980 and 1987. All 830 mammograms were reviewed on two consecutive days in randomized sequence by each reader, and rated 0-3 for each of four criteria including positioning and image quality, with a total possible score of 0-12. Although the mammograms were not in temporal sequence when reviewed, the scores assigned by each reader were significantly higher for mammograms dating from later years. Subjects' ages at entry (40-49 vs 50-59 years) did not affect the score. The largest increase in scores was associated with a 1985 protocol change in which mediolateral oblique positioning replaced straight mediolateral positioning. This study reinforces the importance of monitoring technical quality in screening programs and establishes that the NBSS benefited from technical improvements during its operation. A retrospective review of NBSS mammography by three external reviewers confirmed that technical quality improved from 1980 to 1987. This improvement was associated with improved technology (film, processing, and units) and with the quality assurance programs operating during the NBSS, which identified problems and offered remedies.

Adult↗
PubMed1990

The sinusoidal harmonic acceleration rotary chair test. Theoretical and clinical basis.

Sinusoidal harmonic acceleration has become a common method used in diagnostic vestibular testing. When properly used, it can produce normal and abnormal patterns that can be interpreted in the context of the nature of the stimulus and the physiologic processes that describe the responses to it. Thus, the aim of this review is to present specific information regarding the sinusoidal harmonic acceleration stimulus and vestibular physiology in a way that will hopefully aid in test interpretation.

Acceleration↗
PubMed1989

Cigarette smoking and breast cancer: case-control studies of prevalent and incident cancer in the Canadian National Breast Screening Study.

Two case-control studies of Canadian women aged 40-59 years are reported investigating the relation of cigarette smoking with initial visit (prevalent) and subsequent visit (incident) breast cancer detection, respectively, within the Canadian National Breast Screening Study. The analysis of prevalent breast cancer (1982-1985), which involved 254 cases and 762 controls, showed no evidence of an elevated risk for women with a history of cigarette smoking, with odds ratios of 0.9 (95% confidence interval (Cl) 0.6-1.5) and 1.2 (95% Cl 0.8-1.8) in premenopausal and postmenopausal subjects, respectively. Similarly, in the incident breast cancer analysis (1981-1987) based on 317 cases and 951 controls, women with a history of cigarette smoking had odds ratios of 1.2 (95% Cl 0.8-2.0) and 1.2 (95% Cl 0.9-1.7) in the premenopausal and postmenopausal categories, respectively. No evidence of dose response or of elevated risk in ex-smokers or current smokers was found in either study. These results persisted despite adjustment for several important variables. The present data demonstrate no association between smoking and prevalent or incident breast cancer in either menopausal category, contradicting the authors' previous finding of a positive association with premenopausal prevalent disease earlier in this screening study. The relation of smoking and breast cancer remains controversial. Further study is required to determine whether an association truly does not exist or whether smoking might have both protective and harmful effects that are mediated through different pathways, thus accounting for the paradoxical findings in the literature to date.

Adult↗
PubMed1989

Earth horizontal axis rotational responses in patients with unilateral peripheral vestibular deficits.

We evaluated the vestibulo-ocular reflex (VOR) of five patients with surgically confirmed unilateral peripheral vestibular lesions. Testing used both earth vertical axis (EVA) and earth horizontal axis (EHA) yaw rotation. Results indicated that the patients had short VOR time constants, asymmetric responses to both EVA and EHA rotation, and normal EHA modulation components. These findings suggest that unilateral peripheral vestibular loss causes a shortened VOR time constant even with the addition of dynamic otolithic stimulation and causes an asymmetry in semicircular canal-ocular reflexes and one aspect of otolith-ocular reflexes.

Aged↗
PubMed1989

Eyes open versus eyes closed: effect on human rotational responses.

The effect of eyelid closure on the response to rotational vestibular stimulation was assessed by evaluating 16 normal human subjects with both earth vertical axis (EVA) and earth horizontal axis (EHA) yaw rotations with either eyes closed (EC) or eyes open in the dark (EOD). Results indicated that for EVA rotation, the subjects' responses were of larger magnitude and less variable with EOD than with EC. However, for EHA rotation, responses were of larger magnitude and equally variable with EC as compared to EOD. Our data also indicated that the quality of the EHA response with EC was altered because eyelid closure influenced the amount of periodic gaze. We conclude that eyelid closure has an effect upon both canalocular and otolithocular reflexes and suggest that both EVA and EHA rotational testing be performed with EOD rather than with EC.

Adult↗
PubMed1979

Oral administration of BCG as an adjuvant to surgical treatment of carcinoma of the bronchus.

A controlled clinical trial of the value of bacille Calmette--Guérin (BCG) vaccine given orally to patients with resectable carcinoma of the lung was conducted in 18 centres across Canada. A total of 308 patients were included in the analysis, 155 in the BCG group and 153 in the control group. The two groups were similar at the time of admission to the trial. BCG (120 mg) was given orally at weekly intervals for 1 month, every 2 weeks up to 3 months and then every 3 months until the total duration of therapy was 18 months. Over a 3- to 5-year follow-up period after the operation there was no difference in survival between the two groups, the proportion alive at 2 years being 61% in the BCG group and 58% in the control group. There was also no evidence of differences in the time to the detection of recurrent or metastatic disease or in the distribution of such disease. An analysis of prognostic factors confirmed the poor survival associated with histologically confirmed lymph node involvement. It may be concluded that no favourable effect from the oral administration of BCG was demonstrated.

Adjuvants, Immunologic↗
PubMed1979

Transient persistence of neural activity after periodic stimulation in the cat LGN.

Oscillatory neural activity recorded from gross concentric electrodes implanted in the lateral geniculate nucleus (LGN) of cat was investigated after trains of periodic electrical shock stimulation were applied to the contralateral optic nerve. Spectral analysis using repeated trials and spectral averaging revealed statistically significant spectral peaks (p less than 0.05) at the stimulus frequency when there was a 0.5 to 1.5 s delay between the last pulse of the stimulus train and the beginning of the data analysis window. This suggests that a loosely coupled neuronal net may allow for the continuation of activity far longer than the time accounted for by neuronal time constants and delays.

Animals↗
PubMed1979

Entrainment of oscillatory neural activity in the cat's lateral geniculate nucleus.

Oscillatory neural activity in the frequency range 7-12 Hz is observed in the lateral geniculate nucleus (LGN) of the lightly anesthetized cat. This paper describes a series of experiments in which the interactions between ongoing oscillatory potentials and periodic photic and electrical stimuli are analyzed using frequency domain techniques. The principal results of these experiments are consistent with a model of the neural system as an entrainable oscillator in which ongoing oscillations are suppressed by stimulation at nearby frequencies, but coexist with stimulus frequencies farther away. The physiological interpretation of these results may be closely tied to the role of the LGN as a "gating" mechanism between retina and cortex.

Alpha Rhythm↗