A variant of uncertain significance in SDHAF1, the succinate dehydrogenase chaperone protein, in an adult patient with spastic paraparesis and leukoencephalopathy.

Succinate dehydrogenase (SDH), or respiratory complex II, consists of four nuclear-encoded subunits. The chaperone protein succinate dehydrogenase assembly factor 1 (SDHAF1) plays an essential role in the assembly of SDH, and in the incorporation of iron-sulfur clusters into the SDHB subunit. SDHB couples the oxidation of succinate to fumarate with the reduction of ubiquinone (coenzyme Q) to ubiquinol. Previously reported mutations in SDHAF1 have been associated with infantile leukoencephalopathy. We report an adult case with a homozygous variant of uncertain significance (VUS) mutation in SDHAF1, presenting with dementia, spastic paraparesis, and cardiomyopathy, initially diagnosed as multiple sclerosis.

Failure mode and effects analysis of the universal anaesthesia machine in two tertiary care hospitals in Sierra Leone.

BACKGROUND: Anaesthesia care in developed countries involves sophisticated technology and experienced providers. However, advanced machines may be inoperable or fail frequently when placed into the austere medical environment of a developing country. Failure mode and effects analysis (FMEA) is a method for engaging local staff in identifying real or potential breakdowns in processes or work systems and to develop strategies to mitigate risks. METHODS: Nurse anaesthetists from the two tertiary care hospitals in Freetown, Sierra Leone, participated in three sessions moderated by a human factors specialist and an anaesthesiologist. Sessions were audio recorded, and group discussion graphically mapped by the session facilitator for analysis and commentary. These sessions sought to identify potential barriers to implementing an anaesthesia machine designed for austere medical environments-the universal anaesthesia machine (UAM)--and also engaging local nurse anaesthetists in identifying potential solutions to these barriers. RESULTS: Participating Sierra Leonean clinicians identified five main categories of failure modes (resource availability, environmental issues, staff knowledge and attitudes, and workload and staffing issues) and four categories of mitigation strategies (resource management plans, engaging and educating stakeholders, peer support for new machine use, and collectively advocating for needed resources). CONCLUSIONS: We identified factors that may limit the impact of a UAM and devised likely effective strategies for mitigating those risks.

Paraneoplastic myopathy: response to intravenous immunoglobulin.

Necrotizing myopathy is an unusual and severe form of paraneoplastic myopathy in which inflammation is minimal or absent. We report two cases of necrotizing myopathy which demonstrated significant response to intravenous immunoglobulin (IVIG) (one in spite of tumor progression). A third case represents the first association of anti-signal recognition particle (anti-SRP) syndrome with large-cell lung cancer. These cases highlight the role of histopathologic diagnosis in directing the treatment of paraneoplastic myopathy, and the role for IVIG in treatment of the syndrome.

Hydrogen peroxide damages the zinc-binding site of zinc-deficient Cu,Zn superoxide dismutase.

Mutations in Cu,Zn superoxide dismutase (Cu,Zn SOD) account for approximately 20% of cases of familial amyotrophic lateral sclerosis (ALS), a late-onset neurodegenerative disease affecting motor neurons. These mutations decrease protein stability and lower zinc affinity. Zinc-deficient SOD (Cu,E SOD) has altered redox activities and is toxic to motor neurons in vitro. Using bovine SOD, we studied the effects of hydrogen peroxide (H(2)O(2)) on Cu,E SOD and Cu,Zn SOD. Hydrogen peroxide treatment of Cu,E SOD inactivated zinc binding activity six times faster than superoxide dismutase activity, whereas inactivation of dismutase activity occurred at the same rate for both Cu,Zn SOD and Cu,E SOD. Zinc binding by Cu,E SOD was also damaged by simultaneous generation of superoxide and hydrogen peroxide by xanthine oxidase plus xanthine. Although urate, xanthine, and ascorbate can protect superoxide dismutase activity of Cu,Zn SOD from inactivation, they were not effective at protecting Cu,E SOD. Hydrogen peroxide induced subtle changes in the tertiary structure but not the secondary structure of Cu,E SOD as detected by near and far UV circular dichroism. Our results suggest that low levels of hydrogen peroxide could potentially enhance the toxicity of zinc deficient SOD to motor neurons in ALS by rendering zinc loss from SOD irreversible.

Ballistic helmets and aspects of their design.

The head represents approximately 9% of the body area exposed in combat yet receives approximately 20% of all "hits." The desirability of protecting this vital structure would appear self-evident. Helmet design is a complex issue. Factors that designers of United States Army helmets thoughtfully consider include weight, ballistic qualities of the construction material, balance, helmet-to-person interface (comfort), maintenance of vision and hearing, equipment and weapon compatibility, ease of modification, available materials and manufacturing techniques, durability, ease of decontamination, disposability, and cost. The envisioned future role of the infantryman will make the interplay among these factors even more daunting.

Liposome-delivered superoxide dismutase prevents nitric oxide-dependent motor neuron death induced by trophic factor withdrawal.

Inhibition of nitric oxide synthesis prevents rat embryonic motor neurons from undergoing apoptosis when initially cultured without brain-derived neurotrophic factor. Using an improved cell culture medium, we found that the partial withdrawal of trophic support even weeks after motor neurons had differentiated into a mature phenotype still induced apoptosis through a process dependent upon nitric oxide. However, nitric oxide itself was not directly toxic to motor neurons. To investigate whether intracellular superoxide contributed to nitric oxide-dependent apoptosis, we developed a novel method using pH-sensitive liposomes to deliver Cu, Zn superoxide dismutase intracellularly into motor neurons. Intracellular superoxide dismutase prevented motor neuron apoptosis from trophic factor withdrawal, whereas empty liposomes, inactivated superoxide dismutase in liposomes or extracellular superoxide dismutase did not. Neither hydrogen peroxide nor nitrite added separately or in combination affected motor neuron survival. Our results suggest that a partial reduction in trophic support induced motor neuron apoptosis by a process requiring the endogenous production of both nitric oxide and superoxide, irrespective of the extent of motor neuron maturation in culture.

Induction of nitric oxide-dependent apoptosis in motor neurons by zinc-deficient superoxide dismutase.

Mutations in copper, zinc superoxide dismutase (SOD) have been implicated in the selective death of motor neurons in 2 percent of amyotrophic lateral sclerosis (ALS) patients. The loss of zinc from either wild-type or ALS-mutant SODs was sufficient to induce apoptosis in cultured motor neurons. Toxicity required that copper be bound to SOD and depended on endogenous production of nitric oxide. When replete with zinc, neither ALS-mutant nor wild-type copper, zinc SODs were toxic, and both protected motor neurons from trophic factor withdrawal. Thus, zinc-deficient SOD may participate in both sporadic and familial ALS by an oxidative mechanism involving nitric oxide.

Myeloperoxidase and horseradish peroxidase catalyze tyrosine nitration in proteins from nitrite and hydrogen peroxide.

Nitration of tyrosine residues in proteins occurs in a wide range of inflammatory diseases involving neutrophil and macrophage activation. We report that both myeloperoxidase (MPO) and horseradish peroxidase (HRP) utilize nitrite (NO2-) and hydrogen peroxide (H2O2) as substrates to catalyze tyrosine nitration in proteins. MPO was approximately 10 times more effective than HRP as a nitration catalyst of bovine serum albumin (BSA). Nitration of BSA by MPO did not require chloride as a cofactor. Physiologic levels of chloride did not significantly inhibit nitration by MPO. Oxidation of chloride to hypochlorous acid (HOCl) is catalyzed by MPO but not by HRP, yet HRP also catalyzed nitration from hydrogen peroxide plus nitrite. Therefore, HOCl formation was not obligatory for tyrosine nitration. Although HOCl plus nitrite can nitrate the amino acid tyrosine in simple solutions, protein nitration by HOCl plus nitrite was not observed in heart homogenates, probably due to the presence of multiple alternative targets of both HOCl and HOCl plus nitrite. In contrast, MPO catalyzed nitration of many proteins in rat heart homogenates using NO2- plus H2O2, suggesting that peroxidase-catalyzed nitration of tyrosine could occur in the presence of competing substrates in vivo. HOCl could substitute for H2O2 as the oxidizing substrate for nitration of either BSA or tissue homogenates catalyzed by either peroxidase. Activated neutrophils may generate nitrotyrosine by several mechanisms, including peroxynitrite, HOCl plus nitrite, and a chloride-independent mechanism involving MPO, nitrite, and hydrogen peroxide.

Decreased zinc affinity of amyotrophic lateral sclerosis-associated superoxide dismutase mutants leads to enhanced catalysis of tyrosine nitration by peroxynitrite.

Mutations to Cu/Zn superoxide dismutase (SOD) linked to familial amyotrophic lateral sclerosis (ALS) enhance an unknown toxic reaction that leads to the selective degeneration of motor neurons. However, the question of how >50 different missense mutations produce a common toxic phenotype remains perplexing. We found that the zinc affinity of four ALS-associated SOD mutants was decreased up to 30-fold compared to wild-type SOD but that both mutants and wild-type SOD retained copper with similar affinity. Neurofilament-L (NF-L), one of the most abundant proteins in motor neurons, bound multiple zinc atoms with sufficient affinity to potentially remove zinc from both wild-type and mutant SOD while having a lower affinity for copper. The loss of zinc from wild-type SOD approximately doubled its efficiency for catalyzing peroxynitrite-mediated tyrosine nitration, suggesting that one gained function by SOD in ALS may be an indirect consequence of zinc loss. Nitration of protein-bound tyrosines is a permanent modification that can adversely affect protein function. Thus, the toxicity of ALS-associated SOD mutants may be related to enhanced catalysis of protein nitration subsequent to zinc loss. By acting as a high-capacity zinc sink, NF-L could foster the formation of zinc-deficient SOD within motor neurons.

The Environmental Symptoms Questionnaire: corrected computational procedures for the alertness factor.

The Environmental Symptoms Questionnaire (ESQ) provides a systematic and quantitative measurement of acute mountain sickness (AMS) as well as other symptoms resulting from exposure to various climatic or stressful conditions. The questionnaire yields factor scores for nine distinct symptom groups. The computational procedures for one of the factors, Alertness, were incorrect as reported in the original manuscript (2). This paper gives the correct procedures and their rationale.

Comparison of behavioral treatments for Raynaud's disease.

Induced vasodilation by classical conditioning was compared to biofeedback therapy as treatment for idiopathic Raynaud's disease. Classical conditioning therapy consisted of 54 10-min immersions of both hands in water (43 degrees C) simultaneously with whole-body exposure to cold air (0 degrees C), given three times per day, 3 days per week, for 6 weeks. Biofeedback therapy consisted of eight sessions of electromyograph feedback (frontalis) while listening to relaxation tapes, followed by 10 sessions of digital thermal feedback while listening to relaxation tapes. Both groups received 10-min cold stress tests of whole-body exposure to 0 degrees C before and after treatments. Results indicated that both therapies significantly increased the digital temperature response to cold. Although no differences between classical conditioning and biofeedback were found at the end of training, a 1-year follow-up indicated that classical conditioning was more effective.

Induced vasodilation as a home treatment for Raynaud's disease.

Ten patients with Raynaud's disease treated themselves at home using induced vasodilation 3 times/day, every other day, for 18 treatment days. The patients, dressed in indoor clothing, immersed both hands in warm tap water (43-45 degrees C) for 8-10 min while exposed to naturally occurring ambient cold. Results of pre- and posttreatment cold exposures showed a significant mean increase in digital temperature of 3.4 degrees C (p less than .001). Conditioning therapy appears to be an effective, feasible alternative to drug or surgical therapy.

Permeability of the blood-brain barrier is not changed by vasoactive doses of arachidonic acid or prostaglandins in rats.

Charles River, Sprague-Dawley rats of both sexes were anesthetized with pentobarbital sodium, 50 mg/kg i.p. and a jugular vein and femoral artery cannulated. Saline, arachidonic acid (1, 2, 4 or 6 mg/kg) alone or 15 minutes after administration of indomethacin (5 mg/kg), prostaglandin E2 (0.5, 1, 2 or 4 micrograms/kg) (PGE2), prostaglandin F2 alpha (20, 40, 80 or 160 micrograms/kg) (PGF2 alpha) or prostaglandin I2 (prostacyclin) (0.5, 1, 2 or 4 micrograms/kg) (PGI2) were given intravenously. Each of the drugs caused a dose-dependent decrease in blood pressure except for PGF2 alpha which caused an initial, short-lasting fall in blood pressure followed by a more sustained rise in blood pressure. The permeability of the blood-brain barrier was measured using 99mTc-sodium pertechnetate (TcO-4). None of the prostaglandins or arachidonic acid caused a significant change in the permeability of the blood-brain barrier. This provides a further example of a dissociation between drug-induced changes in systemic blood pressure and change in the permeability of the blood-brain barrier.

Voluntary dehydration and alliesthesia for water.

The purpose of this experiment was to explore the complex relationship between fluid consumption and consumption factors (thirst, voluntary dehydration, water alliesthesia, palatability, work-rest cycle) during a simulated 14.5-km desert walk (treadmill, 1.34 m X s-1, 5% grade, 40 degrees C dry bulb/26 degrees C wet bulb, and wind speed of approximately 1.2 m X s-1). Twenty-nine subjects were tested (30 min X h-1, 6 h) on each of two nonconsecutive days. The subjects were randomly assigned to one of three groups: tap water (n = 8), iodine-treated tap water (n = 11), or iodine-treated flavored tap water (n = 10). The temperature of the water was 40 degrees C during one trial and 15 degrees C on the other. Mean sweat losses (6 h) varied between 1.4 kg (warm iodine-treated; 232 +/- 44 g X h-1) and 3.0 kg (cool iodine-treated flavored; 509 +/- 50 g X h-1). Warm drinks were consumed at a lower rate than cool drinks (negative and positive alliesthesia). This decreased consumption resulted in the highest percent body weight losses (2.8 and 3.2%). Cooling and flavoring effects on consumption were additive and increased the rate of intake by 120%. The apparent paradox between reduced consumption concomitant with severe dehydration and hyperthermia is attributed to negative alliesthesia for warm water rather than an apparent inadequacy of the thirst mechanism. The reluctance to drink warm iodine-treated water resulted in significant hyperthermia, dehydration, hypovolemia, and, in two cases, heat illness.

Increased metabolism contributes to increased resting ventilation at high altitude.

Ventilatory acclimation to high altitude results in an increase in total or minute ventilation, and is associated with a fall in alveolar PCO2, i.e. alveolar hyperventilation. However, the extent to which the increase in total ventilation is matched by a greater metabolic rate (VO2, VCO2) vs alveolar hyperventilation is unclear. We sought to determine the contribution of changes in metabolic rate to the increase in minute ventilation observed during exposure to high altitude. In 12 healthy male subjects taken from Denver, Colorado (1600 m) to Pikes Peak, Colorado (4300 m) for 5 days, resting minute ventilation increased from low to high altitude (+ 26% for the 5 days) and arterialized PCO2 fell. Resting metabolic rate increased 16% for the 5 days and could account for more than half of the increase in minute ventilation. Among subjects the increases in ventilation on days 1, 2 and 4 were positively correlated with increased CO2 production; they were not correlated with arterial oxygen saturation on any day. During exercise at high altitude, PCO2 values were not different from those at rest and minute ventilation rose above low altitude values (+ 58% by day 5), but the increase could not be accounted for by an increased CO2 production. Thus at rest but not during exercise a substantial portion of the rise in minute ventilation could be attributed to increased metabolic rate.

Hypocapnia and sustained hypoxia blunt ventilation on arrival at high altitude.

Hypoxia at high altitude stimulates ventilation, but inhibitory influences in the first days after arrival limit the ventilatory response. Possible inhibitory influences include hypocapnia and depression of ventilation during sustained hypoxia. Our approach was to compare hypoxic ventilatory responses at low altitude with ventilation at high altitude. In 12 subjects we compared responses both to isocapnic hypoxia and poikilocapnic (no CO2 added) hypoxia during acute (less than 10 min) and sustained (30 min) hypoxia in Denver (1,600 m) with ventilations measured on each of 5 days on Pikes Peak (4,300 m). On Pikes Peak, day 1 ventilation [minute ventilation = 10.0 1/min, BTPS; arterial O2 saturation (Sao2) = 82%] was less than predicted by either acute isocapnic or poikilocapnic tests. However, sustained poikilocapnic hypoxia (Sao2 approximately = 82%) in Denver yielded ventilation similar to that on Pikes Peak on day 1. By Pikes Peak days 4 and 5, endtidal PCO2, pHa, and Sao2 approached plateaus, and ventilation (12.4 1/min, BTPS) on these days was as predicted by the acute isocapnic test. Thus the combination of hypocapnia and sustained hypoxia may have blunted the ventilatory increase on Pikes Peak day 1 but apparently not after 4 or 5 days of acclimatization.

Variable inhibition by falling CO2 of hypoxic ventilatory response in humans.

Acute hypoxia stimulates an increase in ventilation but the resulting hypocapnia limits the magnitude of the increase. Thus the hypoxic ventilatory response is usually measured during isocapnia, but this may not reflect events at high altitude. We hypothesized that the degree of inhibition by hypocapnia might depend on individual ventilatory response to CO2 and thus vary between persons. To test this hypothesis we compared the isocapnic hypoxic ventilatory response (end-tidal PCO2 maintained by CO2 addition) with the response in which CO2 was not added and the end-tidal PCO2 fell to a variable extent (poikilocapnic hypoxia). In 14 healthy persons we found that the poikilocapnic hypoxic ventilatory response was determined by two factors: sensitivity to isocapnic hypoxia acting to increase ventilation and sensitivity to CO2 acting to decrease the hypoxic ventilatory response. The ventilatory response to poikilocapnic hypoxia correlated with but was generally less than the isocapnic hypoxic response. The magnitude of the difference between them related to the hypercapnic response. Further, the results suggested that the CO2 response in the high CO2 range related to ventilatory events in the low CO2 range. Thus the magnitude of ventilatory inhibition by hypocapnia may depend on individual ventilatory responsiveness to CO2.

Procedures for the measurement of acute mountain sickness.

Although acute mountain sickness (AMS) has been studied for well over a century, a standard measure or index of the degree of illness for use in experimental research does not exist. This paper outlines a definition and procedures for an operational measurement of AMS using the Environmental Symptoms Questionnaire (ESQ). After 58 men completed over 650 ESQs during a stay of 1-3 weeks atop Pike's Peak (4300 m), factor analysis produced nine distinct symptom groups, with two factors representing AMS. The first factor contains symptoms indicative of cerebral hypoxia and is labeled AMS-C. The second reflects respiratory distress and is called AMS-R. Signal detection theory was used to establish a criterion score value for each factor. Standard deviation values were used to derive indices of sickness severity. Discussion is given to the possible relationships between the two types of AMS and the more serious conditions of cerebral and pulmonary edema.