On the removal of air-borne droplets by the human respiratory tract: II. The nasal passages

Theoretical considerations lead to the calculation of the amounts of air-borne materials removed by the various regions of the human nasal passages. These calculations are presented and discussed in the light of available data and lead to the conclusion that impaction due to inertia is the principle factor in the removal of the air-borne particles of diameters greater than one micron. The work described in this paper was done in part under contract between the Medical Division, Chemical Corps, U. S. Army, and The University of Chicago Toxicity Laboratory. Under terms of the contract the Chemical Corps neither restricts nor is responsible for the opinions or conclusions of the author.     

The health risks of new-wave vegetarianism

Many young people call themselves vegetarians because they don''t eat meat, but the eating style they are adopting is fraught with health risks. In this article, which won CMAJ''s 1996 Army Chouinard Memorial Essay Contest for Canadian journalism students, Laura Brydges Szabo looks at the "new vegetarianism" and the recommendations health care professionals are making to young people intent on following this incomplete diet. The contest encourages journalism students to write on health care topics.     

On the removal of air-borne droplets by the human respiratory tract: I. The lung

Calculations as to the fate of air-borne particles in the respiratory tract are given in a paper by W. Findeisen (1935). It is the purpose of the present paper to extend and modify these calculations. The results obtained for total retention in the lungs are found to be in general agreement with published data (cf. Landahl and Herrmann, 1948). The calculated results also give information on the amounts deposited in various regions as well as the amounts retained in different fractions of expired air. The work described in this paper was done in part under contract between the Medical Division, Chemical Corps, U. S. Army, and the University of Chicago Toxicity Laboratory. Under the terms of the contract the Chemical Corps neither restricts nor is responsible for the opinions or conclusions of the author.     

Prevention should be the preferred insurance program for all physicians.

Recent fee increases announced to the Canadian Medical Protective Association (CMPA) and the Ontario government''s plan to stop its CMPA rebate program for the province''s physicians have put the spotlight on medical liability insurance. In this examination of the role played by the CMPA, Ottawa lawyer Karen Capen notes that quality service and attention to physician-patient communication will in most cases ensure a litigation-free professional life.     

A survey of postgraduate training for family practice.

The results of a survey of Canadian primary care physicians for the Canadian Medical Association (CMA''s) Task Force on Education for the Provision of Primary Care Services are reported. Recent Canadian medical school graduates in primary care practice reported that the three major training routes (rotating and mixed internships and family medicine residencies) each prepared them differently for practice. The graduates of 2-year family medicine residencies were more satisfied with their preparation than were the graduates of the other major training routes. A 2- or 3-year family medicine residency was preferred by 50% of the respondents, although only 33% of them had actually taken one of these routes. There was considerable agreement in the respondents'' assessments of the types of postgraduate education needed for primary care practice. The results of this survey were consistent with the recommendations in the final report of the CMA''s task force.     

Canadian military physician one of many who tried to help Rwandans cope with a "world of hurt".

Lieutenant-Commander Colin Harwood was part of a team from the Canadian Forces Medical Service (CFMS) that was sent to Rwanda in the wake of that country''s bloody civil war. The Ottawa-based officer says the CFMS personnel helped ease many serious medical problems during the 10 weeks they spent there, although the sheer numbers of wounded, diseased and orphaned people sometimes seemed overwhelming. The Canadian personnel helped more than 22,000 patients during their stay.     

Buffeted by harsh economic winds,medical schools turn a wary eye to the future

All parts of Canada''s health care system are facing fiscal pressures these days, but they are particularly great at Canada''s medical schools. However, Dr. David Hawkins of the Association of Canadian Medical Colleges is optimistic that all 16 of Canada''s medical schools will remain open, mainly because of the huge impact they have on health care in their local communities. “We don''t just turn out students — we raise the standard of health care in a whole community,” he says.     

孕期应激下调成年雄性子代大鼠海马HDAC2表达

目的明确母代大鼠孕期应激对雄性子代海马中组蛋白去乙酰化酶2(histone deacetylase 2, HDAC2)表达变化的影响。方法将16只SD孕鼠随机分为应激组和对照组,每组8只,应激组在孕16-21天进行限制性应激,对照组不做任何处理。ELISA检测成年子代外周血血浆糖皮质激素,用旷场、高架十字迷宫、新物体识别及巴恩斯迷宫四种行为学评估成年子代认知功能,免疫组织化学、Western blot、RT-PCR 检测成年雄性子代海马HDAC2表达变化。结果母代孕期应激成年子代糖皮质激素升高,旷场与高架十字迷宫中表现出焦虑样行为,新物体识别与Barnes迷宫表现出学习记忆与空间记忆能力下降,海马HDAC2 mRNA和蛋白水平均下调。结论孕期应激对子代成年的认知功能损害可能与子代海马HDAC2的表达下调有关。     

ACMC: past,present and future.

In this article, the president of the Association of Canadian Medical Colleges (ACMC) and its director of research review the issues that have confronted ACMC since its inception: the founding of ACMC; development of the clinical teaching unit; creation of the Medical Research Council and expansion of the research mission; the Royal Commission on Health Services and the founding of new faculties of medicine; ACMC''s in-house research program; accreditation and ACMC''s links with medical education in the United States; and French-language medical education in Canada. The review points out the perennial nature of many of these issues, and how often perceived solutions to the problems later become problems themselves. It ends on the optimistic note that ACMC can successfully meet the challenges of the future.     

October induction ceremony will coincide with official opening of Canadian Medical Hall of Fame

Seven of medicine''s leaders will be inducted into the Canadian Medical Hall of Fame during a special ceremony in London, Ont., on Oct. 5. The 1995 inductees are Drs. Henry Barnett, Bruce Chown, Herbert Jasper, Charles Leblond, William Mustard, Robert Salter and Michael Smith.     

Dubin calls on CMPA to eliminate fee differentials,adopt flat fee for all physicians

Charles Dubin''s massive review of the Canadian Medical Protective Association supports the CMPA''s policy of maintaining a large reserve for malpractice coverage, but calls for a major overhaul of the association''s fee structure. Regardless of the risks their practices pose, says Dubin, all doctors should pay the same fee in order to keep physicians practising in high-risk specialties such as obstetrics and orthopedic surgery. The alternative, said CMPA president Dr. Bill Thomas, is an exodus from certain specialties because of massive bills for malpractice insurance.     

Growth hormone therapy in Canada: end of one era and beginning of another.

This paper reviews the difficulties in diagnosing a true deficiency of growth hormone (GH), the long-term results of therapy, the Canadian experience in treating GH deficiency, including the contributions made by the Medical Research Council''s Therapeutic Trial of Human Growth Hormone, and the occurrence of Creutzfeldt-Jakob disease in recipients of GH therapy. It also speculates on potential alternatives to treatment with GH derived from human pituitaries.     

A quantitative ranking of Canada's research output of original human studies for the decade 1989 to 1998

BACKGROUND: Since 1987 research articles have been catalogued with the author''s affiliation address in the 40 databases of the Medical Literature Analysis and Retrieval System (MEDLARS) of the National Library of Medicine, Bethesda, Md. The present study was conducted to examine the Canadian entries in MEDLARS to interpret past and future trends and to combine the MEDLARS demographic data with data from other sources to rank Canadian research output of human studies both nationally and internationally. METHODS: The PubMed Web site of the National Library of Medicine was used to count medical articles archived in MEDLARS and published from Jan. 1, 1989, through Dec. 31, 1998. The articles attributed to Canadian authors were compared by country, province, city, medical school, hospital, article type, journal and medical specialty. RESULTS: During the study period Canadian authors contributed on average 3% (standard deviation [SD] 0.2%) of the worldwide MEDLARS content each year, which translated to a mean of 11,067 (SD 1037) articles per year; 49% were human studies, of which 13% were clinical or controlled trials, and 55% involved people aged 18 years or less. In total, 68% of the articles were by authors affiliated with Canadian medical schools; those affiliated with the University of Toronto accounted for the greatest number (8604), whereas authors affiliated with McGill University had the greatest rate of annual increase in the quantity published (8%). Over one-third (38%) of the articles appeared in Canadian journals. When counted by specialty, 17% of the articles were by authors with clinical specialties, 5% by those with surgical specialties and 3% by those with laboratory specialties. INTERPRETATION: The annual rate of increase in research output for Canada was more than 3 times higher than that seen world wide. Canada is now ranked seventh among countries contributing human studies to MEDLARS. The increase indicates that Canada''s medical schools are productive, competitive in making contributions to medical science and are supporting Canadian journals.     

Defining the physician's duty to warn: consensus statement of Ontario's Medical Expert Panel on Duty to Inform

Ontario''s Medical Expert Panel on Duty to Inform was formed to consider the duty of Ontario physicians in circumstances where a patient threatens to kill or cause serious bodily harm to a third party. The panel was concerned about the implications of any duty to inform on the integrity of the physician-patient relationship, particularly with respect to confidentiality. The panel agreed that regulations safeguarding the confidentiality of patient information ought to be changed only if there is a critical reason for doing so, but, after deliberation, the panel members concluded that the need to protect the public from serious risk of harm is a paramount concern that should supersede the duty of confidentiality. The recommendations reported here were endorsed in principle by the panelists and the groups they represented (the Royal College of Physicians and Surgeons of Canada, the Canadian Medical Protective Association, the College of Physicians and Surgeons of Ontario, the Ontario College of Family Physicians and the Ontario Medical Association) and are being implemented by the College of Physicians and Surgeons of Ontario.     

Is deleting the digital rectal examination a good idea?

Although the supply of physicians in the United States has doubled during the past 20 years, there is still disagreement as to whether we currently have or should expect a significant surplus of physicians. The evidence suggests that despite the rapid expansion in the pool of available physicians, serious physician shortages persist for certain rural populations, ethnic and occupational groups, and other medically disadvantaged segments of the population. Medical students'' declining interest in rural practice and primary care specialties suggests that problems of geographic and specialty maldistribution may worsen despite a rising population of physicians. It is unlikely that a significant physician surplus will develop unless there is a conscious attempt to limit the proportion of national wealth expended on medical care. Pockets of shortage can be reduced by broadening the availability of health insurance, lessening large income disparities between different specialties, changing the way teaching institutions are reimbursed for their training costs, and supporting direct governmental service programs such as the National Health Service Corps.     

Coupled intra- and interdomain dynamics support domain cross-talk in Pin1

The functional mechanisms of multidomain proteins often exploit interdomain interactions, or “cross-talk.” An example is human Pin1, an essential mitotic regulator consisting of a Trp–Trp (WW) domain flexibly tethered to a peptidyl-prolyl isomerase (PPIase) domain, resulting in interdomain interactions important for Pin1 function. Substrate binding to the WW domain alters its transient contacts with the PPIase domain via means that are only partially understood. Accordingly, we have investigated Pin1 interdomain interactions using NMR paramagnetic relaxation enhancement (PRE) and molecular dynamics (MD) simulations. The PREs show that apo-Pin1 samples interdomain contacts beyond the range suggested by previous structural studies. They further show that substrate binding to the WW domain simultaneously alters interdomain separation and the internal conformation of the WW domain. A 4.5-μs all-atom MD simulation of apo-Pin1 suggests that the fluctuations of interdomain distances are correlated with fluctuations of WW domain interresidue contacts involved in substrate binding. Thus, the interdomain/WW domain conformations sampled by apo-Pin1 may already include a range of conformations appropriate for binding Pin1''s numerous substrates. The proposed coupling between intra-/interdomain conformational fluctuations is a consequence of the dynamic modular architecture of Pin1. Such modular architecture is common among cell-cycle proteins; thus, the WW–PPIase domain cross-talk mechanisms of Pin1 may be relevant for their mechanisms as well.     

Characterization of the structure and function of W --> F WW domain variants: identification of a natively unfolded protein that folds upon ligand binding

The WW domain adopts a compact, three-stranded, antiparallel beta-sheet structure that mediates protein-protein interactions by binding to xPPxY-based protein ligands, such as the PY-ligand (EYPPYPPPPYPSG) derived from p53 binding protein-2. The conserved Trp residues, after which this domain was named, were replaced with Phe so their importance in structural integrity and for ligand binding could be evaluated. A biophysical approach was employed to compare the W17F, W39F, and W17F/W39F WW domains to the wild-type protein. The data demonstrate that replacement of Trp39 with Phe (W39F) does not disrupt the structure of the WW domain variant, but does abolish ligand binding. In contrast, the W17F WW domain variant is largely if not completely unfolded; however, this variant undergoes a PY-ligand induced disorder to order (folding) transition. The dissociation constant for the W17F WW domain-PY-ligand interaction is 15.1 +/- 1.2 microM, only slightly higher than that observed for the wild-type WW domain interaction (5.9 +/- 0.33 microM). The W17F WW domain is a natively unfolded protein which adopts a native conformation upon PY-ligand binding.     

Differences in the Volume of Pharmaceutical Advertisements between Print General Medical Journals

Background

Pharmaceutical advertisements have been argued to provide revenue that medical journals require but they are intended to alter prescribing behaviour and they are known to include low quality information. We determined whether a difference exists in the current level of pharmaceutical advertising in print general medical journals, and we estimated the revenue generated from print pharmaceutical advertising.

Methods

Six print general medical journals in Canada, the United States, and the United Kingdom were sampled between 2007 and 2012. The number of advertisements and other journal content in selected issues of the Canadian Medical Association Journal (CMAJ), Canadian Family Physician (CFP), Journal of the American Medical Association (JAMA), New England Journal of Medicine (NEJM), British Medical Journal (BMJ), and Lancet were determined. Revenue gained from pharmaceutical advertising was estimated using each journal''s 2013 advertising price list.

Findings

The two Canadian journals sampled (CMAJ, CFP) contained five times more advertisements than the two American journals (JAMA, NEJM), and two British journals (BMJ, Lancet) (p<0.0001). The estimated annual revenue from pharmaceutical advertisements ranged from £0.025 million (for Lancet) to £3.8 million (for JAMA). The cost savings due to revenue from pharmaceutical advertising to each individual subscriber ranged from £0.02 (for Lancet) to £3.56 (for CFP) per issue.

Conclusion

The volume of pharmaceutical advertisements differs between general medical journals, with the two Canadian journals sampled containing the most advertisements. International and temporal variations suggest that there is an opportunity for all general medical journals to reduce the number of pharmaceutical advertisements, explore other sources of revenue, and increase transparency regarding sources of revenue.     

Improving hydroturbine pressures to enhance salmon passage survival and recovery

Barotrauma caused by rapid decompression during hydroturbine (turbine) passage may occur as fish move through the low pressure region below the turbine runner. This scenario is of particular concern in North American rivers with populations of ESA-listed salmon. The US Army Corps of Engineers (USACE) and the Pacific Northwest National Laboratory released Sensor Fish into lower Snake and Columbia River turbines to determine the magnitude and rate of pressure change fish might experience. Recorded pressures were applied to simulated turbine passage (STP) in laboratory studies to determine the effect of rapid decompression on juvenile Chinook salmon. These STP studies have increased our understanding of how pressure effects fish passing through turbines and suggest that the ratio of pressure change [acclimation pressure (the depth upstream of the dam where fish are neutrally buoyant) divided by nadir pressure (lowest pressure)] is highly predictive in determining the effect on smolt survival. However, uncertainty remains in smolt acclimation depth prior to entering turbine intakes at hydroelectric facilities. The USACE continues to make progress on salmon survival and recovery efforts through continued research and by applying pressure study results to turbine design. Designing new turbines with higher nadir pressure criteria is likely to provide safer fish passage for all salmonid species experiencing turbine passage.     

Drinking and Driving

Alcohol misuse generates many health and social problems at a cost that society is increasingly unwilling to sustain. One of the most tragic consequences of alcohol misuse is the result of drinking and driving. Each week, impaired drivers kill 40 Canadian men, women and children and injure 1250 others. The Canadian Medical Association (CMA), in its campaign against drinking and driving, has recommended that a condition of obtaining or renewing a driver''s licence include the individual''s written consent to allow the taking of blood samples by qualified medical personnel when deemed necessary by law enforcement agencies. CMA has recommended to the provinces that the legal age for the purchase and public possession of alcohol be raised to 21. CMA also supports the ban of all alcohol advertising in the electronic media and emphasizes that since alcohol is a drug, all containers should be visibly labelled “Misuse of this Product can be Injurious to Health”. CMA continues to support and encourage the federal and provincial governments in their battle to prevent alcohol-related deaths and injuries through education, control of advertising, use of breathalyzer devices, mandatory blood alcohol testing and legislation enacting stiffer penalties for drinking and driving.