The "Gulf War syndrome". Is there evidence of dysfunction in the nervous system?

Co-Administration of Nanowired Monoclonal Antibodies to Inducible Nitric Oxide Synthase and Tumor Necrosis Factor Alpha Together with Antioxidant H-290/51 Reduces SiO2 Nanoparticles-Induced Exacerbation of Pathophysiology of Spinal Cord Trauma

Military personnel are often exposed to silica dust during combat operations across the globe. Exposure to silica dust in US military or service personnel could cause Desert Strom Pneumonitis also referred to as Al Eskan disease causing several organs damage and precipitate autoimmune dysfunction. However, the effects of microfine particles of sand inhalation-induced brain damage on the pathophysiology of traumatic brain or spinal cord injury are not explored. Previously intoxication of silica nanoparticles (50-60 nm size) is shown to exacerbates spinal cord injury induces blood-spinal cord barrier breakdown, edema formation and cellular changes. However, the mechanism of silica nanoparticles-induced cord pathology is still not well known. Spinal cord injury is well known to alter serotonin (5-hydroxytryptamine) metabolism and induce oxidative stress including upregulation of nitric oxide synthase and tumor necrosis factor alpha. This suggests that these agents are involved in the pathophysiology of spinal cord injury. In this review, we examined the effects of combined nanowired delivery of monoclonal antibodies to neuronal nitric oxide synthase (nNOS) together with tumor necrosis factor alpha (TNF-α) antibodies and a potent antioxidant H-290/51 to induce neuroprotection in spinal cord injury associated with silica nanoparticles intoxication. Our results for the first time show that co-administration of nanowired delivery of antibodies to nNOS and TNF-α with H-290/51 significantly attenuated silica nanoparticles-induced exacerbation of spinal cord pathology, not reported earlier.

Activity of Paraoxonase/Arylesterase and Butyrylcholinesterase in Peripheral Blood of Gulf War Era Veterans With Neurologic Symptom Complexes or Post-Traumatic Stress Disorder

OBJECTIVE

Two groups of Gulf War era veterans, one exhibiting blurred vision, balance problems/dizziness, tremors/shaking, and speech difficulty and a second group with post-traumatic stress disorder (PTSD), but not the neurologic syndrome, were assessed for organophosphate-detoxifying enzyme paraoxonase/arylesterase (PON1) and its Q/R isoforms, butyrylcholinesterase (BuChE) and its U/A isoforms and cytokines.

METHODS

Defibrinated peripheral blood was evaluated for enzymes and cytokines.

RESULTS

Trends toward elevation of Th2 cytokines interleukin-4 (IL-4) and IL-13 were observed in subjects with neurologic syndrome. Neither the activities nor isoforms of the enzyme, the neurologic symptoms, nor PTSD had any relationship to wartime deployment to the theater of combat.

CONCLUSION

The negative outcomes described above suggest that exposure to organophosphates or other agents normally detoxified by PON1 and BuChE may not have contributed significantly to neurologic components of Gulf War Illness.

Administration of an amino Acid-based regimen for the management of autonomic nervous system dysfunction related to combat-induced illness

The etiology and pathophysiology of posttraumatic stress disorder (PTSD) remains poorly understood. The nutritional deficiencies associated with the altered metabolic processes of PTSD have not previously been studied in detail. This pilot study measured the reduction in symptoms in 21 military veterans reporting moderate to severe symptoms associated with PTSD. Two amino acid–based medical foods specifically formulated with biogenic amines and other nutrients were administered to study subjects targeting specific neurotransmitter deficiencies resulting from altered metabolic activity associated with PTSD. This study included the Physician Checklist – Military (PCL-M), Short Form General Health Survey (SF-36), and Epworth Sleepiness Scale to measure the change in each subject’s score after 30 days of administration. An average decrease of 17 points was seen in the PCL-M, indicating a reduction in PTSD symptoms (P < 0.001). The mental health component of the SF-36 showed an average 57% increase in the subjects’ mental health rating (P < 0.001). The results of this initial study demonstrate that addressing the increased dietary requirements of PTSD can improve symptoms of the disease while eliminating significant side effects. A larger, double-blind, randomized, placebo-controlled trial is warranted.

Self-reported post-exertional fatigue in Gulf War veterans: roles of autonomic testing

To determine if objective evidence of autonomic dysfunction exists from a group of Gulf War veterans with self-reported post-exertional fatigue, we evaluated 16 Gulf War ill veterans and 12 Gulf War controls. Participants of the ill group had self- reported, unexplained chronic post-exertional fatigue and the illness symptoms had persisted for years until the current clinical study. The controls had no self-reported post-exertional fatigue either at the time of initial survey nor at the time of the current study. We intended to identify clinical autonomic disorders using autonomic and neurophysiologic testing in the clinical context. We compared the autonomic measures between the 2 groups on cardiovascular function at both baseline and head-up tilt, and sudomotor function. We identified 1 participant with orthostatic hypotension, 1 posture orthostatic tachycardia syndrome, 2 distal small fiber neuropathy, and 1 length dependent distal neuropathy affecting both large and small fiber in the ill group; whereas none of above definable diagnoses was noted in the controls. The ill group had a significantly higher baseline heart rate compared to controls. Compound autonomic scoring scale showed a significant higher score (95% CI of mean: 1.72–2.67) among ill group compared to controls (0.58–1.59). We conclude that objective autonomic testing is necessary for the evaluation of self-reported, unexplained post-exertional fatigue among some Gulf War veterans with multi-symptom illnesses. Our observation that ill veterans with self-reported post-exertional fatigue had objective autonomic measures that were worse than controls warrants validation in a larger clinical series.

FMRI reveals abnormal central processing of sensory and pain stimuli in ill Gulf War veterans

Many veterans chronically ill from the 1991 Gulf War exhibit symptoms of altered sensation, including chronic pain. In this study of 55 veterans of a Construction Battalion previously examined in 1995-1996 and 1997-1998, brain activation to innocuous and noxious heat stimuli was assessed in 2008-2009 with a quantitative sensory testing fMRI protocol in control veterans and groups representing three syndrome variants. Testing outside the scanner revealed no significant differences in warm detection or heat pain threshold among the four groups. In the fMRI study, Syndrome 1 and Syndrome 2, but not Syndrome 3, exhibited hypo-activation to innocuous heat and hyper-activation to noxious heat stimuli compared to controls. The results indicate abnormal central processing of sensory and painful stimuli in 2 of 3 variants of Gulf War illness and call for a more comprehensive study with a larger, representative sample of veterans.

Debilitating stresses do not increase blood-brain barrier permeability: Lack of the involvement of corticosteroids

The involvement of corticosteroids in stress-induced change in blood-brain barrier (BBB) permeability was investigated. Mice were adrenalectomized and administered with pyridostigmine bromide (PB) or Evan's blue, markers of BBB penetration, followed by 18-h cold-restraint stress (CRS). Rats were administered with mifepristone, a corticosteroid receptor blocker, and the markers, followed by 4-h water immersion-restraint stress (WIRS). Separately, soman was administered to induce seizures-mediated BBB opening. CRS did not induce PB and Evan's blue penetration, which were not affected by adrenalectomy. Also, the markers were not detected in the brain of rats subjected to WIRS, regardless of the treatment of mifepristone. In comparison, 1-h epileptic seizures increased the penetration of Evan's blue by 875%. The results suggest that in contrast to seizure-related BBB opening, profound stresses do not practically increase the BBB permeability, and that corticosteroids are not involved in the stress-induced BBB penetration of charged chemicals and albumin-dye complex.

Neurotoxic Potential of Depleted Uranium—Effects in Primary Cortical Neuron Cultures and in Caenorhabditis elegans

Depleted uranium (DU) is an extremely dense metal that is used in radiation shielding, counterbalances, armor, and ammunition. In light of the public concerns about exposure to DU and its potential role in Gulf War Syndrome (GWS), this study evaluated the neurotoxic potential of DU using focused studies on primary rat cortical neurons and the nematode Caenorhabditis elegans. We examined cell viability, cellular energy metabolism, thiol metabolite oxidation, and lipid peroxidation following exposure of cultured neurons to DU, in the form of uranyl acetate. We concurrently evaluated the neurotoxicity of uranyl acetate in C. elegans using various neuronal-green fluourescent protein reporter strains to visualize neurodegeneration. Our studies indicate that uranyl acetate has low cytotoxic potential, and uranium exposure does not result in significant changes in cellular energy metabolism, thiol metabolite oxidation, or lipid peroxidation. Furthermore, our C. elegans studies do not show any significant neurodegeneration following uranyl acetate exposure. Together, these studies suggest that DU, in the form of uranyl acetate, has low neurotoxic potential. These findings should alleviate the some of public concerns regarding DU as an etiologic agent of neurodegenerative conditions associated with GWS.

Atmospheric movement of microorganisms in clouds of desert dust and implications for human health

Billions of tons of desert dust move through the atmosphere each year. The primary source regions, which include the Sahara and Sahel regions of North Africa and the Gobi and Takla Makan regions of Asia, are capable of dispersing significant quantities of desert dust across the traditionally viewed oceanic barriers. While a considerable amount of research by scientists has addressed atmospheric pathways and aerosol chemistry, very few studies to determine the numbers and types of microorganisms transported within these desert dust clouds and the roles that they may play in human health have been conducted. This review is a summary of the current state of knowledge of desert dust microbiology and the health impact that desert dust and its microbial constituents may have in downwind environments both close to and far from their sources.

Effects of combined, multiple stressors on pyridostigmine-induced acute toxicity in rats

A number of studies have evaluated the possibility that stress-induced changes in blood-brain barrier permeability enhanced the central effects of the carbamate acetylcholinesterase inhibitor, pyridostigmine. We previously found relatively little evidence of stress-induced changes in the acute toxicity of pyridostigmine in rats using a variety of restraint, forced running and forced swimming stress conditions. In this study, we evaluated the effects of sequential pre-exposure to multiple stressors on the acute toxicity of pyridostigmine. Rats (n = 8 per treatment group) were either un-stressed or stressed by restraint (60 min), forced running (60 min, 15 m/min, 6 degrees incline) and forced swimming (15 min), and then given either vehicle (saline, 1 ml/kg, po) or pyridostigmine (30 mg/kg, po) immediately after the final stressor. Functional signs of cholinergic toxicity (involuntary movements, autonomic dysfunction) were recorded at 0.5, 1 and 2 h after dosing. Body temperature was measured both before stress and 2 h after dosing. Rats were sacrificed immediately after 2-h functional observations to collect tissues (whole blood, diaphragm, frontal cortex, hippocampus and cerebellum) for measurement of cholinesterase activity. Stressed rats treated with pyridostigmine exhibited higher lethality (2/8) compared to unstressed rats given pyridostigmine (0/8). Pyridostigmine elicited classical signs of cholinergic toxicity, but the rats that died did not show increased cholinergic signs and no significant differences in cholinergic signs were noted between treatment groups. Cholinesterase activity was significantly inhibited in blood (47-50%) and diaphragm (80%) following pyridostigmine exposure regardless of stress conditions. Slight but significant inhibition (11-15%) of cerebellar cholinesterase activity was observed following pyridostigmine exposure, but inhibition was not influenced by stress. We conclude that while acute lethality from pyridostigmine may be increased by combined, multiple stressors, increased lethality does not appear due to enhanced cholinergic toxicity or via increased cholinesterase inhibition in either central or peripheral tissues.

Neurological disorders in Gulf War veterans

We present a review of neurological function in Gulf War veterans (GWV). Twenty-two studies were reviewed, including large hospitalization and registry studies, large population-based epidemiological studies, investigations of a single military unit, small uncontrolled studies of ill veterans and small controlled studies of veterans. In nearly all studies, neurological function was normal in most GWVs, except for a small proportion who were diagnosed with compression neuropathies (carpal tunnel syndrome or ulnar neuropathy). In the great majority of controlled studies, there were no differences in the rates of neurological abnormalities in GWVs and controls. In a national US study, the incidence of amyotrophic lateral sclerosis (ALS) seems to be significantly increased in GWVs, compared to the rate in controls. However, it is possible that military service, in general, might be associated with an increased risk of ALS, rather than Gulf War service in particular. Taken together, the conclusion is that if a neurological examination in a GWV is within normal limits, then extensive neurological testing is unlikely to diagnose occult neurological disorders.

Neurodegenerative memory disorders: a potential role of environmental toxins

The hypothesis that neurotoxins may play a role in neurodegenerative disorders remains an elusive one, given that epidemiologic studies often provide conflicting results. Although these conflicting results may result from methodological differences within and between studies, the complexity of chemical disruption of the central nervous system cannot be ignored in attempts to evaluate this hypothesis in different neurodegenerative disorders. Spencer provides a detailed review of the complex processes involved in defining the neurotoxic potential of naturally occurring and synthetic agents. Even concepts such as exposure and dose, as often reported in studies attempting to evaluate the risk imparted by a potential compound, can be deceptive. For example, although dose reflects "that amount of chemical transferred to the exposed subject", factors such as time and concentration in the organism, the ability to access the central nervous system, and how a compound reaches the central nervous system (routes of administration) or secondarily affects other organ systems leading to central nervous system disruption are clearly important to the concept of neurotoxic risk in neurodegenerative disorders. These factors would appear to explain the observed disagreements between studies using animal or neuronal models of neurotoxicity and population-based studies in humans. The importance of these factors and how a potential neurotoxin is investigated are clearly seen in the data on AD and aluminum. In contrast, the impact of MTPT on the central nervous system is more direct and compelling. Added complexity in the study of neurotoxins in human neurodegeneration is derived from data showing that agents may have additive, potentiating, synergistic, or antagonistic effects. Therefore, data from studies evaluating EMF risks could be readily confounded by the presence or absence of heavy metals (eg, arc welding). Other factors that may conceal neurotoxic causes for a given disorder focus on additional features such as genetic predispositions, physiologic changes that occur in aging, and even nutritional status that can support or hinder the affect of a given agent on the central nervous system. Finally, many studies that investigate exposure risk do not readily incorporate the five criteria proposed by Schaumburg for establishing causation. For example, if we apply Schaumburg's first criterion, epidemiologic studies often determines the presence of an agent through history, yet they cannot readily confirm exposure based on environmental or clinical chemical analyses to fulfill this criterion for causation. Additional limitations in research design along with the populations and methods that are sued to study neurotoxins in human neurodegenerative disorders often fail to meet other criteria such as linking the severity and onset with duration and exposure level. Therefore, although studies of agents such as MTPT provide compelling models of neurotoxins and neurodegeneration in humans, disorders such as ALS, PD, and particularly AD will require additional effort if research is to determine the contribution (presence or absence) of neurotoxins to these neurologic disorders.

Neurological status of Australian veterans of the 1991 Gulf War and the effect of medical and chemical exposures

BACKGROUND

Since the 1991 Gulf War, concerns have been voiced about the effects on the health of veterans of Gulf War related medical and chemical exposures.

METHODS

Our cross-sectional study compared 1424 male Australian Gulf War veterans and a randomly sampled military comparison group (n = 1548). A postal questionnaire asked about the presence of current neurological type symptoms, medically diagnosed neurological conditions, and medical and chemical exposures. A neurological examination was performed as part of a physical assessment.

RESULTS

Veterans have a higher prevalence of neurological type symptoms (ratio of means 1.4, 95% confidence interval (CI) 1.2-1.5). Although the odds ratio (OR) of lower limb neurological type symptoms and signs in veterans compared with the comparison group was increased (OR = 1.6, 95% CI 1.0-2.7), it was of borderline significance, and there was no difference between groups according to a Neuropathy Score based on neurological signs alone (ratio of means 1.1, 95% CI 0.9-1.3). The increased OR of neurological type symptoms and signs suggestive of a central nervous system disorder (OR = 1.8, 95% CI 1.0-3.1) was also of borderline significance. Veterans were not more likely to have self-reported medically diagnosed neurological conditions, or to have neurological type symptoms and signs suggestive of an anterior horn cell disorder (OR = 0.9, 95% CI 0.5-1.6). The total number of neurological type symptoms reported by veterans, but not the Neuropathy Score, was associated with Gulf War related exposures including immunizations and pyridostigmine bromide in dose-response relationships, anti-biological warfare tablets, solvents, pesticides, and insect repellents.

CONCLUSIONS

This study shows increased reporting of neurological type symptoms in Gulf War veterans, but no evidence for increased neurological effects based on objective physical signs. There may be a number of factors, including information bias, relating to increased neurological type symptom reporting in veterans.

Organophosphate-Induced Delayed Polyneuropathy

Organophosphate-induced delayed polyneuropathy (OPIDP) is a rare toxicity resulting from exposure to certain organophosphorus (OP) esters. It is characterised by distal degeneration of some axons of both the peripheral and central nervous systems occurring 1-4 weeks after single or short-term exposures. Cramping muscle pain in the lower limbs, distal numbness and paraesthesiae occur, followed by progressive weakness, depression of deep tendon reflexes in the lower limbs and, in severe cases, in the upper limbs. Signs include high-stepping gait associated with bilateral foot drop and, in severe cases, quadriplegia with foot and wrist drop as well as pyramidal signs. In time, there might be significant recovery of the peripheral nerve function but, depending on the degree of pyramidal involvement, spastic ataxia may be a permanent outcome of severe OPIDP. Human and experimental data indicate that recovery is usually complete in the young. At onset, the electrophysiological changes include reduced amplitude of the compound muscle potential, increased distal latencies and normal or slightly reduced nerve conduction velocities. The progression of the disease, usually over a few days, may lead to non-excitability of the nerve with electromyographical signs of denervation. Nerve biopsies have been performed in a few cases and showed axonal degeneration with secondary demyelination. Neuropathy target esterase (NTE) is thought to be the target of OPIDP initiation. The ratio of inhibitory powers for acetylcholinesterase and NTE represents the crucial guideline for the aetiological attribution of OP-induced peripheral neuropathy. In fact, pre-marketing toxicity testing in animals selects OP insecticides with cholinergic toxicity potential much higher than that to result in OPIDP. Therefore, OPIDP may develop only after very large exposures to insecticides, causing severe cholinergic toxicity. However, this was not the case with certain triaryl phosphates that were not used as insecticides but as hydraulic fluids, lubricants and plasticisers and do not result in cholinergic toxicity. Several thousand cases of OPIDP as a result of exposure to tri-ortho-cresyl phosphate have been reported, whereas the number of cases of OPIDP as a result of OP insecticide poisoning is much lower. In this article, we mainly discuss OP pesticide poisoning, particularly when caused by chlorpyrifos, dichlorvos, isofenphos, methamidophos, mipafox, trichlorfon, trichlornat, phosphamidon/mevinphos and by certain carbamates. We also discuss case reports where neuropathies were not convincingly attributed to fenthion, malathion, omethoate/dimethoate, parathion and merphos. Finally, several observational studies on long-term, low-level exposures to OPs that sometimes reported mild, inconsistent and unexplained changes of unclear significance in peripheral nerves are briefly discussed.

Resolving Disputes About Toxicological Risks During Military Conflict

In the last 15 years, the US and UK have fought two major wars in the Persian Gulf region. Controversy has arisen over the nature and causes of health problems among military veterans of these two wars. Toxic exposures have been hypothesised to cause the majority of the long-term health problems experienced by veterans of the 1991 Gulf War. The assessment of these toxic exposures and the resolution of controversy about their health effects provide a unique case study for understanding how toxicological disputes are settled in the US. Neither clinical examination of ill war veterans nor scientific research studies have been sufficient to answer contentious questions about toxic exposures. Numerous expert review panels have also been unable to resolve these controversies except for the US National Academy of Sciences Institute of Medicine (IOM). The IOM has conducted exhaustive and independent investigations based on peer-reviewed scientific literature related to potential health risks during the two Gulf Wars. In four recent studies, IOM committees identified a wide range of previously documented illnesses associated with common occupational and environmental exposures after considering thousands of relevant publications; however, they did not identify a new medical syndrome or a specific toxic exposure that caused widespread health problems among Gulf War veterans. These IOM studies have, therefore, added little to our basic knowledge of environmental hazards because most of the health effects were well known. Nevertheless, this expert review process, which is on-going, has been generally acceptable to a wide range of competing interests because the findings of the IOM have been perceived as scientifically credible and independent, and because none of the postulated toxicological risks have been completely ruled-out as possible causes of ill health among veterans.

Is Gulf War Syndrome really a mystery?

Since the end of the 1991 Gulf War about 20,000 United States veterans and similar proportions of troops from other allied contingents have been affected by a variety of symptoms which have collectively become known as 'Gulf War Syndrome'. Similar symptoms have been reported in Iraqi civilians including children. Despite extensive investigations no agreement has been reached on whether there is an underlying cause or causes. In this article, the principal features of the illness are summarised and some of the proposed causes discussed. It is proposed that the common cause is the toxic smoke from incomplete combustion of oil from burning wells, and this hypothesis is related to the known toxicology of two likely combustion products, nitric oxide and carbon monoxide. The effect of this proposal on possible investigations and treatment is considered.

Clinical and laboratory assessment of distal peripheral nerves in Gulf War veterans and spouses

BACKGROUND

The prevalence of symptoms suggesting distal symmetric polyneuropathy (DSP) was reported to be higher among deployed veterans (DV) to the Persian Gulf in 1990-1991 than to control non-deployed veterans (NDV). The authors therefore compared the prevalence of DSP by direct examination of DV and their spouses to control NDV and spouses.

METHODS

The authors performed standardized neurologic examinations on 1,061 DV and 1,128 NDV selected from a cohort of veterans who previously participated in a national mail and telephone survey. Presence of DSP was evaluated by history, physical examination, and standardized electrophysiologic assessment of motor and sensory nerves. Similar examinations were performed without electrophysiologic tests in 484 DV spouses and 533 NDV spouses. Statistical analyses were performed with appropriate adjustments for the stratified sampling scheme.

RESULTS

No differences between adjusted population prevalence of DSP in DV and NDV were found by electrophysiology (3.7% vs 6.3%, p = 0.07), by neurologic examination (3.1% vs 2.6%, p = 0.60), or by the methods combined (6.3% vs 7.3%, p = 0.47). Excluding veterans with non-military service related diseases that may cause DSP did not alter outcomes. DV potentially exposed to neurotoxins from the Khamisiyah ammunition depot explosion did not significantly differ in DSP prevalence compared to non-exposed DV. The prevalence of DSP in DV spouses did not differ from NDV spouses (2.7% vs 3.2%, p = 0.64).

CONCLUSIONS

Neither veterans deployed during the Gulf War era nor their spouses had a higher prevalence of DSP compared to NDV and spouses.

Combined forced running stress and subclinical paraoxon exposure have little effect on pyridostigmine-induced acute toxicity in rats

Pyridostigmine is a short-acting inhibitor of cholinesterase (ChE) used as a pretreatment against potential nerve agent exposure during the Persian Gulf War. As pyridostigmine contains a quaternary ammonium group, it is generally believed to elicit changes in the peripheral nervous system function only. It has been hypothesized, however, that the neurotoxicity of pyridostigmine may be altered by either stress or combined exposures to other toxicants. We evaluated the effects of forced running stress, exposure to the organophosphate anticholinesterase paraoxon, or a combination of both on the acute neurotoxicity of pyridostigmine. ChE (blood, diaphragm, and selected brain regions) and carboxylesterase (CE; liver, plasma) inhibition was also evaluated. Young adult male Sprague-Dawley rats were either given vehicle or paraoxon (0.1 mg/kg, i.m.) and subsets placed in their home cage or forced to run on a treadmill for 60 min. Pyridostigmine (0, 10 or 30 mg/kg, p.o.) was given 60 min after paraoxon dosing and rats were evaluated for cholinergic toxicity just prior to sacrifice 60 min later. No signs of toxicity were noted following paraoxon exposure while both dosages of pyridostigmine (10 and 30 mg/kg, p.o.) elicited signs of functional toxicity. Toxicity was not different with combined paraoxon-pyridostigmine exposures and forced running did not influence toxicity under any conditions. Paraoxon (0.1 mg/kg, i.m.) caused moderate (23-46%) ChE inhibition in blood, diaphragm and brain 2 h after exposure. Pyridostigmine (10 or 30 mg/kg, p.o.) caused extensive inhibition of blood (88-94%) and diaphragm (75-85%) ChE activity but no significant effect on brain regional ChE activity. Forced running stress did not influence the degree of tissue ChE inhibition following either paraoxon, pyridostigmine or paraoxon-pyridostigmine combined exposures. CE activities were inhibited (26-43%) in plasma and liver by paraoxon but inhibition was not influenced by either stress or combined paraoxon-pyridostigmine exposures. These results suggest that subclinical paraoxon exposure and forced running stress, by themselves or in combination, have little effect on acute pyridostigmine toxicity in rats.

A status report on chronic fatigue syndrome

Medical history has shown that clinical disease entities or syndromes are composed of many subgroups--each with its own cause and pathogenesis. Although we cannot be sure, we expect the same outcome for chronic fatigue syndrome (CFS), a medically unexplained condition characterized by disabling fatigue accompanied by infectious, rheumatological, and neuropsychiatric symptoms. Although the ailment clearly can occur after severe infection, no convincing data exist to support an infectious (or immunologic) process in disease maintenance. Instead, data point to several possible pathophysiological processes: a covert encephalopathy, impaired physiological capability to respond to physical and mental stressors, and psychological factors related to concerns about effort exacerbating symptoms. Each of these is under intense investigation. In addition, some data do exist to indicate that environmental agents also can elicit a state of chronic fatigue. We expect data to accumulate to support the belief that CFS has multiple causes.

Low-level exposures to organophosphorus esters and peripheral nerve function

This review evaluates the epidemiological and clinical evidence linking low-level and prolonged exposures to organophosphorus esters, used as insecticides or nerve agents, to peripheral nerve dysfunction. The clinical effects of large doses of these chemicals-including the cholinergic syndrome, the intermediate syndrome, and the delayed polyneuropathy-are all well established and are summarized. Based on these clinical observations and experimental studies, dose-effect relationships indicate that peripheral neuropathy always develops after cholinergic toxicity. However, several studies have suggested that this relationship may be different after low-level prolonged exposures, as, for instance, those experienced by Gulf War veterans and British sheep farmers, thereby leading to the development of peripheral neuropathy without preceding cholinergic toxicity. A critical assessment of these studies, involving subjects with either current or past exposures, indicates that changes in peripheral nerve function were mild, inconsistent, and unexplained and that most studies lack exposure data. Suggestions made about individual hypersusceptibility to delayed polyneuropathy lack support. It is concluded that there is no evidence of peripheral nerve dysfunction caused by low-level prolonged exposures to organophosphate insecticides or nerve agents.

Posttraumatic stress symptomatology is associated with unexplained illness attributed to Persian Gulf War military service

OBJECTIVE

Controversy exists concerning unexplained illness in Persian Gulf War veterans, especially regarding the contribution of psychological trauma. We sought to determine if war zone trauma or posttraumatic stress symptomatology (PTSS) are associated with illnesses reported by Gulf War veterans that were documented by medical examination but not attributable to a medical diagnosis.

METHODS

A total of 1119 (55% response rate) of 2022 randomly sampled veterans of the United States Persian Gulf War were screened and 237 cases and 113 controls were identified by medical examination for a case-control study comparing Persian Gulf War military veterans with or without medically documented, but unexplained, symptoms. Multivariate logistic regression and cross-validation analyses examined self-report measures of demographics, subjective physical symptoms and functioning, psychiatric symptoms, stressors, war zone trauma, and PTSS, to identify correlates of case-control status.

RESULTS

Posttraumatic stress symptomatology and somatic complaints were independently associated with case status, as were (although less consistently) war zone trauma and depression. Age, education, and self-reported health, stress-related somatization, pain, energy/fatigue, illness-related functional impairment, recent stressors, and anxiety were univariate (but not multivariate) correlates of case status.

CONCLUSIONS

PTSS related to war zone trauma warrants additional prospective research study and attention in clinical screening and assessment as a potential contributor to the often debilitating physical health problems experienced by Persian Gulf War veterans.

The problem of Gulf War syndrome

Following a war with widespread attention to and concern over the potential for numerous biological and chemical warfare exposures, some Gulf War veterans returned home and developed various illnesses. Although some of these illnesses are readily diagnosable, the so-called Gulf War syndrome has remained a controversial and nebulous diagnosis. It is characterized by multiple, subjective symptoms, and by a lack of objective pathology. To date, the search for a single disease entity and a biological model to explain this illness has been unsuccessful. Wars have long affected the health of veterans in multiple ways, and a single disease entity is not likely as a viable explanation for these outcomes. Given the nature of the illness, and its overlap with many other controversial chronic illnesses, we suggest that the biopsychosocial model may provide a better solution to this diagnostic conundrum.

Activation of the coagulation system in Gulf War Illness: a potential pathophysiologic link with chronic fatigue syndrome. A laboratory approach to diagnosis

Most symptoms of Gulf War Illness (GWI) are similar to Chronic Fatigue Syndrome (CFS) and/or Fibromyalgia (FM). We investigated whether these symptoms are associated with an activated coagulation system as has been reported in some cases of CFS/FM. The coagulation assays include activation markers of the cascade, platelet activation and hereditary risk factors. Our findings show activation of the coagulation system in GWI. This evidence of a hypercoagulable state suggests that symptoms may be due to poor blood flow and, therefore, a basis for the potential utility of anticoagulant therapy.

Somatic hypotheses of war syndromes

Since the end of the American Civil War, unexplained symptoms in military personnel arising after a war or peace mission have frequently been described. The pattern of symptoms is highly similar for all of the various war syndromes although the conditions of each war or peace mission are widely different. Many somatic hypotheses have been formulated to explain these syndromes; a considerable proportion of them are already outdated. In the last few years much attention has been given to Gulf War Syndrome and to unexplained symptoms of military personnel who were sent to Cambodia, Rwanda, Burundi, Zaire, or the former Yugoslavia. In this review the symptoms of war syndromes will be considered in more detail and the suggested somatic explanations will be discussed. During the last decade the following somatic causes have been suggested as possible explanations for these symptoms: (persistent) infection, abnormal immune response, administration of multiple vaccinations within a short period of time, use of malaria chemoprophylaxis, neurological abnormalities, exposure to toxicological substances and environmental factors. The various investigations performed to study these hypotheses are discussed. The fact that bias regularly occurs in the course of these investigations is pointed out. For the future, a reliable investigation of a war syndrome should be a prospective multidisciplinary study and should distinguish between causative and sustaining factors.

Is there a Persian Gulf War syndrome? Evidence from a large population-based survey of veterans and nondeployed controls

PURPOSE

Concerns have been raised about whether veterans of the Gulf War have a medical illness of uncertain etiology. We surveyed veterans to look for evidence of an illness that was unique to those deployed to the Persian Gulf and was not seen in comparable military controls.

SUBJECTS AND METHODS

A population-based sample of veterans (n = 1,896 from 889 units) deployed to the Persian Gulf and other Gulf War-era controls (n = 1799 from 893 units) who did not serve in the Gulf were surveyed in 1995-1996. Seventy-six percent of eligible subjects, including 91% of located subjects, answered questions about commonly reported and potentially important symptoms. We used factor analysis, a statistical technique that can identify patterns of related responses, on a random subset of the deployed veterans to identify latent patterns of symptoms. The results from this derivation sample were compared with those obtained from a separate validation sample of deployed veterans, as well as the nondeployed controls, to determine whether the results were replicable and unique.

RESULTS

One half (50%) of the deployed veterans and 14% of the nondeployed controls reported health problems that they attributed to military service during 1990-1991. Compared with the nondeployed controls, the deployed veterans had significantly greater prevalences of 123 of 137 (90%) symptoms; none was significantly lower. Factor analysis identified three replicable symptom factors (or patterns) in the deployed veterans (convergent correlations > or =0.85). However, these patterns were also highly replicable in the nondeployed controls (convergent correlations of 0.95 to 0.98). The three factors also accounted for similar proportions of the common variance among the deployed veterans (35%) and nondeployed controls (30%).

CONCLUSIONS

The increased prevalence of nearly every symptom assessed from all bodily organ systems among the Gulf War veterans is difficult to explain pathophysiologically as a single condition. Identification of the same patterns of symptoms among the deployed veterans and nondeployed controls suggests that the health complaints of Gulf War veterans are similar to those of the general military population and are not consistent with the existence of a unique Gulf War syndrome.

Effects of inescapable stress and treatment with pyridostigmine bromide on plasma butyrylcholinesterase and the acoustic startle response in rats

Pyridostigmine bromide (PB) is a reversible, peripherally active inhibitor of acetylcholinesterase (AChE) activity, and is recommended by the military as a pretreatment against potential nerve gas exposure. Recent evidence suggests that exposure to inescapable stressors allows PB to cross the blood-brain barrier, and thereby affect central AChE activity in mice. Here, we evaluated the functional impact of a stress/PB treatment interaction on acoustic startle responding and plasma butyrylcholinesterase (BuChE) activity in male Sprague-Dawley rats. To model the treatment protocol used by the military, PB was delivered in the drinking water of rats for 7 consecutive days. The morning after the start of PB treatment, and for the next 6 days, half the rats were exposed to 1 h of supine restraint stress. We therefore employed a 2 x 2 (stress x PB treatment) between-groups design. Exposure to supine stress alone induced a persistent decrease in plasma BuChE activity. Further decreases in BuChE activity were not observed in rats exposed to supine restraint and PB treatment. Exposure to stress also induced an exaggerated startle response, evident on the last day of stress and 24 h after stressor cessation. Treatment with PB alone produced an exaggerated startle response over the same time period, albeit to a lesser degree. Although treatment with PB concurrent with stress did not produce further changes in either BuChE activity or acoustic startle responding, stress-induced alterations in drinking behavior (and thereby the dose of PB ingested) may have affected these results. Persistent stress-induced reductions in BuChE activity may increase the risk of adverse reactions to cholinomimetics.

Neurally mediated hypotension in fatigued Gulf War veterans: a preliminary report

BACKGROUND

Many patients with chronic fatigue syndrome (CFS) have neurally mediated hypotension when subjected to head-up tilt, suggesting autonomic nervous system dysfunction. Some Gulf War veterans have symptoms similar to CFS. Whether they also tend to have neurally mediated hypotension is unknown.

METHODS

We performed 3-stage tilt-table testing on 14 Gulf War veterans with chronic fatigue, 13 unfatigued control Gulf War veterans, and 14 unfatigued control subjects who did not serve in the Gulf War. Isoproterenol was used in stages 2 and 3 of the tilt protocol.

RESULTS

More fatigued Gulf War veterans than unfatigued control subjects had hypotensive responses to tilt (P < 0.036). A positive response to the drug-free stage 1 of the tilt was observed in 4 of 14 fatigued Gulf War veterans versus 1 of 27 unfatigued control subjects (P < 0.012). Heart rate and heart rate variation during stage 1 was significantly greater in the fatigued group (P < 0.05).

CONCLUSION

We conclude that more fatigued Gulf War veterans have neurally mediated hypotension than unfatigued control subjects, similar to observations in CFS. Autonomic nervous system dysfunction may be present in some fatigued Gulf War veterans.

Psychiatric diagnoses in Gulf War veterans with fatiguing illness

The purpose of this study was to determine whether Gulf War Illness (GWI) can be explained by the presence of psychiatric disorders as assessed by DSM-III-R. To reduce the heterogeneity amongst Persian Gulf War veterans with GWI (PGV-F), only those were studied who presented with severe fatigue as a major complaint and also fulfilled clinical case definitions for Chronic Fatigue Syndrome, Idiopathic Chronic Fatigue, and/or Multiple Chemical Sensitivity. A total of 95 Registry PGVs were examined; 53 presented with GWI and 42 did not report any post-war health problems (PGV-H). All subjects were assessed for the presence of DSM-III-R Axis I psychiatric disorders. Compared to PGV-Hs, 49% of PGV-Fs had similar post-war psychiatric profiles: either no, or only one, psychiatric disorder was diagnosed. Psychiatric profiles of the remaining 51% of PGV-Fs were significantly different from PGV-Hs in that most of these veterans suffered from multiple post-war psychiatric diagnoses. The presence of psychiatric disorders as assessed by DSM-III-R criteria cannot explain symptoms of Gulf War Illness among all Persian Gulf veterans with severe fatiguing illness.

Pyridostigmine bromide alters locomotion and thigmotaxis of rats: gender effects

Male rats and female rats in the proestrous and metestrous stages of estrus were tested to determine the effects of pyridostigmine bromide on locomotion rate and thigmotactic response using doses of 3.0, 10.0, and 30.0 mg/kg. Thirty minutes after administration of the pyridostigmine bromide the rats were videorecorded for 2 h in a 1 m2 open-field arena. The rats' activities were analyzed for the drug's effect on speed throughout the 2 h and during six 20-min segments. Also, the times that the rats were observed moving through the central 50% of the arena were determined. Locomotion rates decreased significantly, and thigmotaxses increased significantly in all groups of rats as a dose response to pyridostigmine bromide. Habituation occurred over 2 h for both responses, primarily during the first 40 min. Female rats were more affected than males, but metestrous and proestrous females did not differ significantly in their responses. At the 30 mg/kg the effect was persistent throughout the test period. Proestrous females dosed at 30 mg/kg had much higher pyridostigmine bromide serum levels than metestrous females and males.

Patterns of waking EEG spectral power in chemically intolerant individuals during repeated chemical exposures

Previous studies indicate that low level chemical intolerance (CI) is a symptom of several different controversial conditions with neuropsychiatric features, e.g., chronic fatigue syndrome, fibromyalgia, multiple chemical sensitivity, and "Persian Gulf Syndrome". Prior studies suggest that limbic and/or mesolimbic sensitization may contribute to development of CI. The purpose of this report was to document the waking electroencephalographic (EEG) patterns of individuals with CI during chemical exposures presented over repeated sessions. Three groups of adult subjects who were recruited from the community participated in the study: self-reported CI who had made associated lifestyle changes due to their intolerance (CI/ LSC), self-reported CI who had not made such changes (CI), and normal controls without self-reported CI. Subjects underwent two sessions involving one-minute EEG recordings during exposures to low level chemical odors (a probe for limbic activation). The CI, but not the CI/ LSC, subjects had increased absolute delta power after the chemical exposures during the second, but not the first, session. The findings support the neural sensitization hypothesis for intolerance to low levels of environmental chemicals in vulnerable individuals. As in human studies of stimulant drug sensitization, those with the strongest past history with sensitizing agents may not show-term sensitization to low level exposures in the laboratory.

Epidemiological association in US veterans between Gulf War illness and exposures to anticholinesterases

To investigate complaints of Gulf War veterans, epidemiologic, case-control and animal modeling studies were performed. Looking for OPIDP variants, our epidemiologic project studied 249 Naval Reserve construction battalion (CB24) men. Extensive surveys were drawn for symptoms and exposures. An existing test (PAI) was used for neuropsychologic. Using FACTOR, LOGISTIC and FREQ in 6.07 SAS, symptom clusters were sought with high eigenvalues from orthogonally rotated two-stage factor analysis. After factor loadings and Kaiser measure for sampling adequacy (0.82), three major and three minor symptom clusters were identified. Internally consistent by Cronbach's coefficient, these were labeled syndromes: (1) impaired cognition; (2) confusion-ataxia; (3) arthro-myo-neuropathy; (4) phobia-apraxia; (5) fever-adenopathy; and (6) weakness-incontinence. Syndrome variants identified 63 patients (63/249, 25%) with 91 syndromes. With pyridostigmine bromide as the drug in these drug-chemical exposures, syndrome chemicals were: (1) pesticide-containing flea and tick collars (P < 0.001); (2) alarms from chemical weapons attacks (P < 0.001), being in a sector later found to have nerve agent exposure (P < 0.04); and (3) insect repellent (DEET) (P < 0.001). From CB24, 23 cases, 10 deployed and 10 non-deployed controls were studied. Auditory evoked potentials showed dysfunction (P < 0.02), nystagmic velocity on rotation testing, asymmetry on saccadic velocity (P < 0.04), somatosensory evoked potentials both sides (right P < 0.03, left P < 0.005) and synstagmic velocity after caloric stimulation bilaterally (P-range, 0.02-0.04). Brain dysfunction was shown on the Halstead Impairment Index (P < 0.01), General Neuropsychological Deficit Scale (P < 0.03) and Trail Making part B (P < 0.03). Butylcholinesterase phenotypes did not trend for inherent abnormalities. Parallel hen studies at Duke University established similar drug-chemical delayed neurotoxicity. These investigations lend credibility that sublethal exposures to drug-chemical combinations caused delayed-onset neurotoxic variants.

Gulf War veterans' illnesses: a case study in causal inference

The objective of this study was to determine from the published epidemiological literature whether there is evidence for a causal association between service in the Gulf War and illness in U.S. veterans. Eleven published studies were analyzed using standardized epidemiologic criteria for assessing causality. A consistent association was found between deployment to the Gulf and self-reports of symptoms. No consistency was seen in physical findings or laboratory results. Strength of association varied with different study designs. Dose-response information is limited, because of lack of quantitative data on exposures. Biological plausibility varies for different risk factors. Specificity of association is not seen. Frequency of self-reported symptoms is increased in U.S. Gulf War veterans compared to other veterans of the same era, but specific causes of illnesses cannot be ascertained. Major gaps in data that impeded this analysis include (1) lack of objective data on specific environmental exposures (2) lack of baseline health assessments, and (3) lack of objective measures of post-deployment health status. In future deployment of U.S. troops, accurate exposure and health data will be needed if the causes of subsequent illnesses are to be accurately assessed.

Does examination of urinary sediment identify individuals with Gulf War syndrome? A pilot study

BACKGROUND

Many veterans who were involved in the Persian Gulf theater of operations have had a variety of unexplained physical complaints, collectively called the Gulf War syndrome or similar names. There has been much debate on the issue and numerous publications, both in the medical and the lay press. A method for examining urinary sediment that was developed in an effort to identify nonculturable bacteria has been used in Gulf War veterans and was the basis for intensive antimicrobial therapy in many of them.

METHODS

We evaluated eight Gulf War veterans with complaints compatible with Gulf War syndrome. Subjects were from various parts of the United States. A detailed history and physical examination were performed. Urine was obtained before and after prostatic massage (men) or before and after pelvic examinations (women) and was tested by a previously described microscopic method as well as by culture and conventional Gram stain. Age- and sex-matched healthy control subjects were tested similarly and concurrently.

RESULTS

Two female Gulf War veterans had findings of Candida albicans and Klebsiella pneumoniae by conventional culture. The same organism types were seen both by the special method and by conventional Gram stain. All other subjects and controls were completely indistinguishable.

CONCLUSION

Examining the urinary sediment by this elaborate method does not differentiate persons with Gulf War syndrome from normal, healthy control subjects who were never in the Persian Gulf area.

Clinical applications of quantitative sensory testing (QST)

Quantitative sensory testing (QST) has been used clinically for the last two decades, yielding a substantial number of publications regarding these applications. In this review we tried to amass together the major findings of these publications into one monograph, excluding those dealing with pain. This was done with the aim of assisting clinicians in the better use of QST techniques for the benefit of their patients.