Proven Cause Research Articles

Novel TOR1A mutation p.Arg288Gln in early-onset dystonia (DYT1)

Background: The three-nucleotide deletion, GAG (within the gene TOR1A), is the only proven cause of childhood-onset dystonia (DYT1). A potentially pathogenic role of additional sequence changes within TOR1A has not...

Biochemical Characterization of G93A Mutant human Cu, Zn Superoxide Dismutase Purified from Transgenic Rat Spinal cord

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder with no cure and mutations to Cu‐Zn superoxide dismutase (SOD1) remain the only proven cause of the disease. SOD1, a 32‐kDa homodimer, is a ubiquitously expressed cytosolic antioxidant enzyme with one Cu and one Zn per monomer stabilized by an intra‐subunit disulfide (Cys 57 and Cys 146) bond. It also contains two more cysteines (Cys 6 and Cys 111) thought to be present as reduced thiols. To identify the potential mechanisms by which the mutant SOD1 (mSOD1) mediates neurotoxicity, we purified the mSOD1 from pre‐symptomatic and end stage ALS‐associated G93A mutant rat spinal cords (a model for ALS) using simple reverse‐phase preparative HPLC. The purified mSOD1 was characterized in terms of Cu and Zn levels, SOD activity, and thiol content using chromophoric chelation assay, SOD activity assay and thiol assay respectively. Our results indicate that Zn levels were significantly higher in mSOD1 purified from end stage cord to that of pre‐symptomatic cord, however no significant differences were observed in Cu levels and specific activities. Interestingly, thiol assay revealed that Cys 111 exists primarily in an oxidized state with Cys 6 primarily in the reduced state. These results suggest that biochemical impact of altered Zn affinity and cysteine modifications on SOD1 could have important implications in disease progression.

CHRONIC MENTAL STRESS IS A CAUSE OF ESSENTIAL HYPERTENSION: PRESENCE OF BIOLOGICAL MARKERS OF STRESS

1. In searching for biological evidence that essential hypertension is caused by chronic mental stress, a disputed proposition, parallels are noted with panic disorder, which provides an explicit clinical model of recurring stress responses. 2. There is clinical comorbidity; panic disorder prevalence is increased threefold in essential hypertension. Plasma cortisol is elevated in both. 3. In panic disorder and essential hypertension, but not in health, single sympathetic nerve fibres commonly fire repeatedly within an individual cardiac cycle; this appears to be a signature of stress exposure. For both conditions, adrenaline cotransmission is present in sympathetic nerves. 4. Tissue nerve growth factor is increased in both (nerve growth factor is a stress reactant). There is induction of the adrenaline synthesizing enzyme, phenylethanolamine-N-methyltransferase, in sympathetic nerves, an explicit indicator of mental stress exposure. 5. The question of whether chronic mental stress causes high blood pressure, still hotly debated, has been reviewed by an Australian Government body, the Specialist Medical Review Council. Despite the challenging medicolegal implications, the Council determined that stress is one proven cause of hypertension, this ruling being published in the 27 March 2002 Australian Government Gazette. This judgement was reached after consideration of the epidemiological evidence, but in particular after review of the specific elements of the neural pathophysiology of essential hypertension, described above.

Epidemiology of brain tumors

After lagging behind other brain tumor disciplines in the 1980s, the epidemiology of brain tumors is now making progress on several fronts. The Central Brain Tumor Registry in the USA has made a complete description of primary brain tumors available to researchers. International data suggest that environmental components in the etiology of brain tumors are likely to be widely dispersed by geography and demographic subgroups. There are few proven causes of brain tumors: high-dose ionizing radiation, inherited genetic syndromes and AIDs-related brain lymphomas. Promising avenues of research include the role of immune function, genetic components in families, metabolic and DNA-repair pathways and neurocarcinogen exposures.

Challenges in Developing DNA and RNA Biomarkers of Inflammation

Inflammation is now a proven cause of human diseases such as cancer and cardiovascular disease. One potential link between inflammation and disease involves secretion of reactive chemical species by immune cells, with chronic damage to host epithelial cells leading to disease. This suggests pathophysiologically that DNA and RNA damage products are candidate biomarkers of inflammation, both for mechanistic understanding of the process and for risk assessment. Of the current approaches to quantifying DNA damage products, mass spectrometry-based methods provide the most rigorous quantification needed for biomarker development, while antibody-based approaches provide the most practical way to implement biomarkers in a clinical setting. Nonetheless, all approaches are biased by adventitious formation of DNA and RNA damage products during sample processing. Recent studies of tissue-derived DNA biomarkers in mouse models of inflammation reveal significant changes only in DNA adducts derived from lipid peroxidation. These and other observations raise the question of the most appropriate sampling compartment for DNA biomarker studies and highlight the emerging role of lipid damage in inflammation.

Current thinking on genetics of chronic obstructive pulmonary disease

There is growing evidence that genetics plays a role in the development of chronic obstructive pulmonary disease. This review deals with the most recent findings, new methods to detect genetic susceptibility that may be helpful in this field, and how the environment may act on the genetic code of susceptible individuals and chronic obstructive pulmonary disease sufferers. Candidate gene association studies have identified genes that may have roles in the pathogenesis of chronic obstructive pulmonary disease. Not all studies that have found associations between genes and chronic obstructive pulmonary disease phenotypes have been replicated, however. The realization of this challenge in itself is a major step forward and, coupled with exciting new methods to identify susceptibility genes, may provide the impetus to move the field beyond the notion that alpha-1 antitrypsin is the only proven cause of the disease. Candidate gene studies need to be interpreted with caution because of their lack of reproducibility. Genome-wide association studies may offer the best approach to identifying susceptibility genes in chronic obstructive pulmonary disease. Epigenetics needs to be considered in concert with genetic findings.

Tobacco manufacturers’ defence against plaintiffs’ claims of cancer causation: throwing mud at the wall and hoping some of it will stick

Background: In the late 1990s and the early part of this decade, the major US cigarette manufacturers admitted, to varying degrees, that smoking causes cancer and other diseases. Objective: To...

Risk Assessment and Epidemiologic Evidence: Kundi Responds

I appreciate Goldstein’s remarks about the role of epidemiology in risk assessment of environmental hazards and the opportunity to clarify my standpoint. With reference to the International Agency for Research on Cancer’s classification scheme of agents for their carcinogenicity in humans and other schemes such as that of the U.S. Environmental Protection Agency (EPA), Pitot and Dragan (2001) stated in Casarett and Doull’s Toxicology: In spite of the limitations of these classifications, an agent cannot be proven to be carcinogenic for the human unless substantial epidemiologic evidence supporting such a claim is available. Although this statement refers to carcinoma and not to the broader class of chronic diseases, it seems to be very close to my statement (Kundi 2006) that Goldstein criticizes. However, Goldstein particularly emphasizes that I may have meant that “there must be epidemiologic evidence for a chemical to achieve the level of a known or proven cause of a hazard to human health.” The reader may have noticed that I never used the term “proven” (Kundi 2006), and I deliberately did not. In my opinion we cannot reach the level of a proven cause. Our knowledge is always incomplete; although we may be quite sure about a factor causing a disease, it may turn out to be actually unrelated. Using toxicologic evidence, we may conjecture that an agent has a potential to cause human chronic disease, but we need further evidence—in most cases epidemiologic evidence—to establish a causal relationship between the agent and a chronic disease in humans. (I make a conceptual difference between “establishing” and “proving,” the latter defined as “establishing truth,” which can only be done for analytical statements.) My statement that Goldstein criticizes was misleading insofar as it seems to indicate that we have to start from epidemiologic evidence to ascribe an agent a hazardous potential for human health. In many cases first information on a potential hazard will stem from routine toxicologic testing. The last paragraphs of my commentary (Kundi 2006) were intended to give an outlook to future developments that may provide answers to the question of causation of chronic diseases in a more rapid fashion. From this context it should be clear that risk assessment was addressed with respect to the causal role of an agent. Therefore, a slight modification of the statement above is appropriate: An agent cannot be established to cause a chronic human disease unless supporting epidemiologic evidence is available. Among other improvements, comprehensive utilization of modern molecular biological methods integrated into epidemiologic designs may provide such evidence at an early stage of the disease.

Risk Assessment and Epidemiologic Evidence in Environmental Health Science

There appears to be a serious conceptual error about the role of the various environmental health sciences in Kundi’s otherwise interesting and informative commentary on “Causality and the Interpretation of Epidemiologic Evidence” (Kundi 2006). This error is exemplified in his next-to-last paragraph: Most risk assessment procedures demand that for chronic diseases such as cancer there must be epidemiologic evidence before an extrinsic agent can be ascribed a hazardous potential for human health. In fact, it is solely toxicologic evidence that is used for the overwhelming majority of agents to which a “hazardous potential for human health” is ascribed. I am unaware of any risk assessment process that requires epidemiology to recognize hazardous potential for human health. Perhaps Kundi (2006) meant that there must be epidemiologic evidence for a chemical to achieve the level of a known or proven cause of a hazard to human health. However, the misunderstanding in the above quote permeates his commentary. As Kundi (2006) correctly recognized, it is better to prevent the introduction or use of agents that would cause adverse effects eventually identifiable in an epidemiologic study. Such prevention is primarily the role of predictive toxicology. Yet, as Kundi stated in his abstract, his recommended dialogue approach to “the potential for disease causation” starts with epidemiology. Kundi (2006) concluded that the principle that every disease has a cause is metaphysical, but still has heuristic value. He appears to mean that the principle of causation helps us explore the potential that environmental factors cause human disease—and that we do so by developing models, such as risk assessment, that approximate reality without achieving certainty. However, a risk assessment, or any other model, that must depend on epidemiologic evidence to recognize the potential for disease causation represents a failure of environmental health science.

Questions and Answers

Questions and Answers

Inner ear and facial nerve complications of acute otitis media with focus on bacteriology and virology

Conclusion. Among 20 patients with inner ear complications and/or peripheral facial palsy secondary to acute otitis media (AOM) a proven or probable bacteriological cause was found in 13 (65%). In seven patients (35%), a proven or probable viral cause was found. Only two of the patients (10%), with a proven bacterial AOM and a clinical picture of a purulent labyrinthitis in both, together with a facial palsy in one, had a substantial degree of dysfunction. Although the number of patients in this study is relatively low our findings show that inner ear complications and facial palsy due to AOM can be of both bacterial and viral origin. Severe sequelae were found only where a bacterial origin was proven. Objectives. Inner ear complications and/or peripheral facial palsy secondary to AOM are rare. The general understanding is that they are due to bacterial infections. However, in some of these patients there are no clinical or laboratory signs of bacterial infections and they have negative bacterial cultures. During recent years different viruses have been isolated from the middle ear or serologically proven in AOM patients and are thought to play a pathogenetic role. We suggest that in some cases of AOM complications from the inner ear and the facial nerve can be caused by viruses. The purpose of our study was to analyze infectious agents present in patients with inner ear complications and/or facial palsy arising from AOM. Patients and methods. The medical records of 20 patients who had inner ear complications and/or facial palsy following AOM ( unilateral in 18, bilateral in 2) between January 1989 and March 2003 were evaluated. Bacterial cultures were carried out for all patients. Sera from 12 of the patients were stored and tested for a battery of specific viral antibodies. In three patients, investigated between November 2002 and March 2003, viral cultures were also performed on samples from the middle ear and nasopharynx. Results. Nineteen patients had inner ear symptoms. Eight of them had a unilateral sensorineural hearing loss and vertigo, three had vertigo as an isolated symptom and one, with bilateral AOM, had bilateral sensorineural hearing loss. Seven patients had a combination of facial palsy and inner ear symptoms (unilateral sensorineural hearing loss in three, unilateral sensorineural hearing loss and vertigo in two, bilateral sensorineural hearing loss and vertigo in one, with bilateral AOM, and vertigo alone in one). One patient had an isolated facial palsy. Healing was complete in 11 of the 20 patients. In seven patients a minor defect remained at follow-up (a sensorineural hearing loss at higher frequencies in all). Only two patients had obvious defects (a pronounced hearing loss in combination with a moderate to severe facial palsy (House-Brackman grade 4) in one, distinct vestibular symptoms and a total caloric loss in combination with a high-frequency loss in the other. Eight patients had positive bacteriological cultures from middle ear contents: Streptococcus pneumoniae in two, beta-hemolytic Streptococcus group A in two, beta-hemolytic Streptococcus group A together with Staphylococcus aureus in one, Staph. aureus alone in one and coagulase-negative staphylococci (interpreted as pathogens) in two. In the 12 patients with negative cultures, there was a probable bacteriological cause due to the outcome in SR/CRP and leukocyte count in five. In four patients serological testing showed a concomitant viral infection that was interpreted to be the cause (varicella zoster virus in two, herpes simplex virus in one and adenovirus in one.) In three there was a probable viral cause despite negative viral antibody test due to normal outcome in SR/CRP, normal leukocyte count, serous fluid at myringotomy and a relatively short pre-complication antibiotic treatment period.

Chronic fatigue syndrome: the nurse's role.

Chronic fatigue syndrome (CFS), a disorder of no proven cause, is characterised by extended periods of extreme, debilitating fatigue and related symptoms. This article discusses this distressing disorder and identifies the needs of those who have it. The authors suggest that the nurse could fulfil the role of key professional carer, interacting with the individual with CFS to co-ordinate care and form the pivotal therapeutic relationship. CFS remains a chronic illness of uncertain cause and prognosis. For those with CFS, care priorities involve validation, information and advocacy, a therapeutic relationship and co-ordinated care. The particular philosophy of care held by nurses makes them potentially ideal co-ordinators of care for those with CFS.

Cause and Outcome of Atypical Chest Pain in Patients Admitted to Hospital

In patients with acute chest pain the prime need, usually, is to diagnose and treat myocardial infarction or ischaemia. When a cardiac origin for the pain has been excluded, patients are commonly discharged without either a diagnosis or a plan for follow-up. We studied a group of such patients to see how far causation was pursued and how their mortality compared with that of patients with a proven cardiac cause for their symptoms. The study population was 250 patients admitted over five weeks with chest pain suspected of being cardiac in origin. Initial assessment included an electrocardiogram and measurement of troponin T. If neither of these indicated a cardiac event, the patient was deemed to have ‘atypical’ chest pain and the cause, where defined, was recorded. Outcomes at one year were determined by questionnaire and by assessment of medical notes. Of the 250 patients, 142 had cardiac pain (mean age 79 years, 58% male) and 108 atypical chest pain (mean age 60 years, 55% male). Of those with atypical pain, 40 were discharged without a diagnosis; in the remaining 68 the pain was thought to be musculoskeletal (25), cardiac (21), gastrointestinal (12) or respiratory (10) in origin. 41 patients were given a follow-up appointment on discharge. At one year, data were available on 103 (96%) patients. The mortality rate was 2.9% (3 patients) compared with 18.3% in those with an original cardiac event. Half of the patients with atypical pain had undergone further investigations and 14% had been readmitted. The yield of investigative procedures was generally low (20%) but at the end of the year only 27 patients remained undiagnosed. Patients with atypical chest pain form a substantial proportion of emergency admissions. The symptoms often persist or recur. The commonest causation is musculoskeletal, but a sizeable minority remain undiagnosed even after follow-up.

Cause and outcome of atypical chest pain in patients admitted to hospital.

In patients with acute chest pain the prime need, usually, is to diagnose and treat myocardial infarction or ischaemia. When a cardiac origin for the pain has been excluded, patients are commonly discharged without either a diagnosis or a plan for follow-up. We studied a group of such patients to see how far causation was pursued and how their mortality compared with that of patients with a proven cardiac cause for their symptoms. The study population was 250 patients admitted over five weeks with chest pain suspected of being cardiac in origin. Initial assessment included an electrocardiogram and measurement of troponin T. If neither of these indicated a cardiac event, the patient was deemed to have 'atypical' chest pain and the cause, where defined, was recorded. Outcomes at one year were determined by questionnaire and by assessment of medical notes. Of the 250 patients, 142 had cardiac pain (mean age 79 years, 58% male) and 108 atypical chest pain (mean age 60 years, 55% male). Of those with atypical pain, 40 were discharged without a diagnosis; in the remaining 68 the pain was thought to be musculoskeletal (25), cardiac (21), gastrointestinal (12) or respiratory (10) in origin. 41 patients were given a follow-up appointment on discharge. At one year, data were available on 103 (96%) patients. The mortality rate was 2.9% (3 patients) compared with 18.3% in those with an original cardiac event. Half of the patients with atypical pain had undergone further investigations and 14% had been readmitted. The yield of investigative procedures was generally low (20%) but at the end of the year only 27 patients remained undiagnosed. Patients with atypical chest pain form a substantial proportion of emergency admissions. The symptoms often persist or recur. The commonest causation is musculoskeletal, but a sizeable minority remain undiagnosed even after follow-up.

Sympathetic nerve activity and neurotransmitter release in humans: translation from pathophysiology into clinical practice.

There has been a revolution in cardiovascular neuroscience in recent years with, in some cases, translation into clinical practice of the knowledge of pathophysiology gained through application of sympathetic nerve recording and catecholamine isotope dilution methodology. OBESITY-RELATED HYPERTENSION: An earlier hypothesis, based on findings in most models, was that weight gain in obesity is due in part to sympathetic nervous underactivity reducing thermogenesis. Microneurography and regional noradrenaline spillover measurements in human obesity have disproven this hypothesis, weakening the case for the use of beta3-adrenergic agonists to stimulate thermogenesis. Sympathetic nerve firing rates in post-ganglionic fibres directed to the skeletal muscle vasculature are increased, as is renal sympathetic tone, with a doubling of the spillover rate of noradrenaline from the kidneys. Given these findings, antiadrenergic antihypertensive drugs may be the preferred agents for obesity-related hypertension, but this has not been adequately tested. Whether stress causes high blood pressure, previously hotly debated, has been under recent review by an Australian Government body, the Specialist Medical Review Council. Despite medicolegal implications, the ruling was that stress is one proven cause of hypertension. The judgment was reached after consideration of the epidemiological evidence, but in particular the described neural pathophysiology of essential hypertension: (a) persistent sympathetic nervous stimulation is commonly present, (b) suprabulbar projections of noradrenergic brainstem neurones are activated and (c) adrenaline is released as a cotransmitter in sympathetic nerves. These were taken to be biological markers of stress. At one time, the failing heart was thought to be sympathetically denervated. Longterm administration of inotropic adrenergic agonists, to provide the cardiac catecholamine stimulation thought to be lacking, increased mortality. Noradrenaline isotope dilution methodology subsequently demonstrated that the sympathetic outflow to the heart was preferentially activated, cardiac noradrenaline spillover being increased as much as 50-fold. The level of stimulation of the cardiac sympathetic nerves was the most powerful predictor of death. These observations provide the theoretical foundation for the very successful introduction of beta-adrenergic blockers for treatment of heart failure.

Cerebrovascular mortality in patients with pituitary adenoma.

To assess cerebrovascular mortality in a UK cohort of patients with pituitary adenoma known to have increased incidence of cerebrovascular accidents (CVA). A total of 334 patients treated at the Royal Marsden Hospital (RMH) between 1962 and 1986 with surgery and postoperative radiotherapy were followed up via the NHS Central Register (NHSCR) to identify deaths and emigrations. The causes of death were assessed by NHSCR-based death certificates and coded according to the 9th revision of ICD. Follow-up was censored at age 85, on emigration or cancellation of NHSCR. Thirteen patients could not be traced. A total of 4982 person-years was accumulated in the cohort. Expected numbers of deaths were computed from the national age-, sex- and period-specific mortality rates for England and Wales. In the pituitary adenoma cohort, 128 deaths were observed compared to 80.9 expected [relative risk (RR) of death 1.58 (95% CI: 1.32-1.90)]. There were 33 cerebrovascular deaths compared with 8.04 expected (RR 4.11, 95% CI 2.84-5.75). Three deaths were from subarachnoid haemorrhage compared to 0.54 expected (RR 5.51, 95% CI 1.14-16.09). There was an increased cerebrovascular mortality in women (RR 6.93, 95% CI 4.29-10.60) compared to men (RR 2.4, 95% CI 1.24-4.20; P = 0.002) and in patients having debulking surgery (RR 5.19, 95% CI 3.50-7.42) compared to biopsy/no surgery (RR 1.33, 95% CI 0.27-3.88; P = 0.02). The RR in patients with nonsecretory tumours was 3.65 (95% CI 2.26-5.58), compared with 5.23 (95% CI 2.25-10.30) in secretory tumours (P = 0.4). The effect of age at radiotherapy was not significant (P = 0.4). Patients with pituitary adenoma treated with surgery and radiotherapy have an increased risk of cerebrovascular mortality compared to the general population, which mirrors the increased incidence of CVA. The possible risk factors include hypopituitarism, radiotherapy and extent of surgery but none are at present proven causes. The evaluation of new treatment strategies should not only assess intermediate end-points of tumour and endocrine control but should concentrate on long-term survival with particular emphasis on CVA incidence and mortality.

Reproductive failure and endocrine disruption by organohalogens in fish-eating birds

Effects of organohalogens in fish-eating birds in the field have been monitored largely by studying reproductive outcome in contaminated populations or, at the individual level, by studying the sexual behaviour, egg production, or embryonal and postnatal development and survival. Endocrine disruption has been suggested as a mechanism, but proven cause–effect relationships between specific compounds and endocrine disruption with subsequent reduced reproductive outcome in fish-eating birds are scarce. The effects of organochlorines on hormone metabolism and circulating steroid levels are reviewed and discussed in relation to observed reproductive failures in the field.

Recruitment of the Mitochondrial-Dependent Apoptotic Pathway in Amyotrophic Lateral Sclerosis

Molecular mechanisms of apoptosis may participate in motor neuron degeneration produced by mutant superoxide dismutase-1 (mSOD1), the only proven cause of amyotrophic lateral sclerosis (ALS). Consistent with this, here we show that the proapoptotic protein Bax translocates from the cytosol to the mitochondria, whereas cytochrome c translocates from the mitochondria to the cytosol in spinal cords of transgenic mSOD1 mice during the progression of the disease. Concomitantly, caspase-9 is activated in the spinal cord of transgenic mSOD1 mice. Only in end-stage transgenic mSOD1 mice is the downstream caspase-7 activated and the inhibitor of apoptosis, XIAP, cleaved. These results indicate a sequential recruitment of molecular elements of the mitochondrial-dependent apoptotic pathway in transgenic mSOD1 mice. We also provide immunohistochemical evidence that cytochrome c translocation occurs in the spinal cord of sporadic ALS patients. Collectively, these data suggest that the mitochondrial-dependent apoptotic pathway may contribute to the demise of motor neurons in ALS and that targeting key molecules of this cascade may prove to be neuroprotective.

Is Chlamydia an Independent Risk Factor for Cervical Cancer

Although infection with human papillomavirus (HPV) is a proven cause of cervical squamous cell carcinoma (SCC), data regarding Chlamydia trachomatis

The validation of biodynamic models

Biodynamic models may: (i) represent understanding of how the body moves (i.e., `mechanistic models'), (ii) summarise biodynamic measurements (i.e., `quantitative models'), and (iii) provide predictions of the effects of motion on human health, comfort or performance (i.e., `effects models'). Model validation may involve consideration of evidence used to derive a model, comparison of the model with alternatives, and a comparison between model predictions and independent observations of the predicted qualities or quantities. Models should be associated with a specified range of independent and dependent variables and indicate how intra-subject variability and inter-subject variability are accommodated. Models of the mechanisms of body movement may be validated by demonstrations that the mechanisms are well represented. Models giving numerical predictions (`quantitative models' and `effects models') should specify the expected accuracy of predictions. `Effects models' advocated for predicting health, comfort or performance require that: (i) vibration or shock is a proven cause of the specified effect, (ii) within all reasonable ranges of model inputs, there must be reason to expect a positive correlation and acceptable error between the model predictions and the effect, (iii) other variables having a large influence on the effect must be taken into consideration. It is more useful to report the accuracy of `quantitative models' and `effects models' models than to state that they are `validated' or `un-validated'. Checklists for assessing the quality of a biodynamic model are proposed, taking into account the type of model and the model assertions, the evidence, the assumptions, the accuracy, and the appropriateness of the model. Relevance Biodynamic models can be used to predict risks of injury or disease. Models can be used to optimise designs in order to minimise predicted risks. However, models can be promulgated and used without knowledge of their accuracy or usefulness.