Mechanism of action of sodium cyanide on rat diaphragm muscle.

The effects of sodium cyanide (NaCN) were investigated on the contractile and electrophysiological properties of rat diaphragm muscles in vitro. Sodium cyanide (0.1-1.0 mM) produced an initial potentiation of directly elicited twitch tensions, followed by a slow progressive depression. The potentiation and depression were both dependent on the NaCN concentration and stimulation frequency. Muscles exposed to NaCN exhibited marked reductions of creatine phosphate concentration, but ATP levels were not significantly lowered. Sodium cyanide had no effect on the resting potential, input resistance or action potential, indicating that the toxicity of the metabolic inhibitor is not mediated by alterations of membrane excitability or passive electrical properties. Sodium cyanide reduced the amplitude of contractures elicited by 70 mM K(2)SO(4), suggesting that the actions of NaCN cannot be explained by a failure of action potentials to propagate across the muscle surface or within t-tubular membranes. Sodium cyanide suppressed the first phase of the caffeine contracture, an observation consistent with an impaired release of, or reduced sensitivity to, sarcoplasmic reticular Ca(2+), but did not alter the amplitude of the second phase, which represents rigor following ATP depletion. These results, in conjunction with those of previous studies, suggest that the depression in muscle tension following exposure to NaCN may result from alterations in Ca(2+) homeostasis, intracellular acidosis or from accumulation of one or more products of phosphocreatine breakdown.     

Evaluation of phosphoramidon and three synthetic phosphonates for inhibition of botulinum neurotoxin B catalytic activity

Three putative metalloprotease inhibitors were synthesized and tested for their ability to inhibit the catalytic activity of botulinum neurotoxin B light chain (BoNT/B LC). The compounds were designed to emulate the naturally occurring metalloprotease inhibitor phosphoramidon, which has been reported to be a weak antagonist of BoNT/B action. All three analogs contained the dipeptide Phe-Glu in place of Leu-Trp of phosphoramidon and possessed a phenyl, ethyl or methyl group in place of the rhamnose sugar of the parent compound. The inhibitors were evaluated in a cell-free assay based on the detection of a fluorescent product following cleavage of a 50-mer synaptobrevin peptide ([Pya(88)] S 39-88) by BoNT/B LC. This peptide corresponds to the hydrophilic core of synaptobrevin-2 and contains a fluorescent analog L-pyrenylalanine (Pya) in place of Tyr(88). Cleavage of [Pya(88)] S 39-88 by BoNT/B LC gives rise to fragments of 38 and 12 amino acid residues. Quantification of BoNT/B-mediated substrate cleavage was achieved by separating the 12-mer fragment (FETSAAKLKRK-Pya) that contains the C-terminal fluorophore and measuring fluorescence at 377 nm. The results indicate that the phenyl-substituted synthetic compound ICD 2821 was slightly more active than phosphoramidon, but analogs with methyl or ethyl substitutions were relatively inactive. These findings suggest that phosphonate monoesters may be useful for providing insights into the structural requirement of BoNT/B protease inhibitors.     

Limb preservation for reimplantation. a review

Although reimplantation of severed limbs and other parts of the body has become prevalent in recent years, the questions of how best to preserve limbs for reimplantation and how to determine if a transected part is viable have not been fully answered. The problem of preservation involves combating direct anoxic damage to tissue as well as combating the changes in the vascular system that lead to the "no reflow phenomenon." Current information concerning kidney preservation as well as experimental and clinical reports on limb preservation are reviewed in this article, and suggestions are made for further investigations.     

National health accounts: lessons from the U.S. experience

The national health accounts (NHA) are the framework within which type of services and sources of funding for health care expenditures are measured. NHA, devised to portray the structure of health care delivery and financing in the United States, provide essential information necessary for the formulation of public health policy and for international comparison. In this article, the authors describe the importance of the NHA nationally and internationally, and provide a blueprint of the definitions, sources, and methods used to create this system of NHA in the United States.     

Patient-based health status assessments in an outpatient psychiatry setting

OBJECTIVE: The reliability, validity, and feasibility of the routine use of a generic health status instrument, the Short-Form-36 Health Survey (SF-36), were examined in a psychiatric outpatient clinic of a general hospital. METHODS: The sample comprised 411 patients referred to an outpatient psychiatry department between April 1994 and March 1995. They filled out the SF-36 along with their admission forms. Scores and reports were generated, and the results were returned to the charts and used at weekly clinical conference discussions. Feasibility was evaluated using subjective and objective data on administration of the instrument, its psychometric properties, and costs. Results from the outpatient psychiatry patients were compared with those from patients scheduled for elective surgery and a healthy normative sample. RESULTS: Routine administration of the SF-36 was successfully achieved with minimal resistance from staff and patients. The SF-36 provided reliable and valid data. As predicted, patients with emotional disorders scored lower, indicating more impairment, on scales measuring mental health than did the elective surgery patients and the normative sample. However, the psychiatric patients' scores on the physical health scale were lower than clinicians expected. Compared with the elective surgery patients, the psychiatric patients were less impaired on only the physical functioning and bodily pain scales; no difference was found between the two groups in role functioning due to physical problems. CONCLUSIONS: Routine use of the SF-36 in a general hospital psychiatric outpatient clinic was feasible, and the results were reliable, valid, and helpful to clinicians. Psychiatric patients' significantly lower scores in physical health and social and role functioning provided additional information about their difficulties.     

Blood-brain barrier disruption and complement activation in the brain following rapid correction of chronic hyponatremia

In previous studies we developed a rat model in which demyelination is reproducibly produced following rapid correction of chronic hyponatremia and demonstrated that the development of demyelination in this model is strongly associated with NMR indices of blood-brain barrier (BBB) disruption. Because complement is toxic to oligodendrocytes, we evaluated the hypothesis that BBB disruption precipitated by correction of hypoosmolality is followed by an influx of complement into the brain, which then contributes to the demyelination that occurs under these conditions. We studied four groups of rats with immunocytochemical analysis using primary antibodies to IgG and the C3d split-fragment of activated complement: (1) normal rats; (2) rats in which hyponatremia was maintained for 7 days; (3) chronically hyponatremic rats in which the plasma [Na(+)] was rapidly corrected with hypertonic saline administration 20 h prior to perfusion; and (4) chronically hyponatremic rats in which the plasma [Na(+)] was rapidly corrected with hypertonic saline administration 5 days prior to perfusion. In normonatremic and uncorrected hyponatremic rats only background staining was observed in areas lacking a BBB and in blood vessel walls, whereas marked increases in IgG and C3d staining were seen in the brains of rats both 20 h and 5 days after rapid correction of hyponatremia. The staining intensity was significantly correlated with the degree of neurological impairment. These results provide evidence for functional BBB disruption following rapid correction of hyponatremia and support the hypothesis that complement activation may be involved in the pathogenesis of osmotic demyelination.     

Analysis of high-frequency electroencephalographic-electromyographic coherence elicited by speech and oral nonspeech tasks in Parkinson's disease.

PURPOSE: Corticomuscular electroencephalographic-electromyographic (EEG-EMG) coherence elicited by speech and nonspeech oromotor tasks in healthy participants and those with Parkinson's disease (PD) was examined. Hypotheses were the following: (a) corticomuscular coherence is demonstrable between orbicularis oris (OO) muscles' EMG and scalp EEG recording; (b) the presence, location, and magnitude of coherence is task specific; (c) differences in corticomuscular coherence patterns exist between healthy and PD participants; and (d) differences will manifest as either increased or decreased coherence values in certain frequency bands, with EEG localization at primary sensorimotor cortex and/or supplementary motor area (SMA). METHOD: Simultaneous EEG, EMG (OO), and speech samples were recorded on 20 healthy and 20 PD participants during speech and nonspeech tasks. Fast Fourier transform and coherence analysis was performed with Neuroscan software on 1,000 randomly generated epochs per task per group. Corticomuscular coherence was analyzed between each EEG electrode and right and left superior and inferior OO muscles up to 200 Hz. Significant coherence peaks exceeded 95% confidence limits (.003). RESULTS: Corticomuscular coherence existed for both groups and for all tasks, but to varying degrees in primary sensorimotor cortex and SMA. CONCLUSIONS: Results support task specificity for both groups and, in PD, a diminished modulation flexibility linked to the sensorimotor area and reduced corticomuscular coherence at the SMA.