Analysis of motor unit firing patterns in patients with central or peripheral lesions using singular-value decomposition

We applied the singular value decomposition (SVD) method to study single motor unit firing patterns. Two projects were carried out: (1) a computer simulation study to confirm the meanings of two SVD parameters, the eigenvalue corresponding to the positive-slope eigenvector (PEV) and that corresponding to the negative-slope eigenvector (NEV); and (2) a clinical study for which electromyographic (EMG) recordings were made from first dorsal interosseous muscle in patients with stroke, myopathies, or neuropathies and in healthy control subjects. Results of computer simulation reveal that the NEV reflects the amount of instantaneous firing variability, whereas the PEV/NEV (P/N) ratio exhibits the relative effect of a trend in the firing pattern. In human studies, the P/N ratio of stroke patients was significantly higher than that of the controls, whereas their NEV was comparable. By contrast, in the myopathy and neuropathy groups, the NEV increased significantly, whereas the P/N ratio did not. These results suggest that the SVD method decomposes the motor unit (MU) firing variation into two components and that the mechanism for increased firing variability is different for supraspinal and spinal-infraspinal lesions.

DNA adduct level in lung tissue may act as a risk biomarker of lung cancer

Lung cancer is a leading cause of mortality in Taiwan. We hypothesised that high susceptibility to DNA damage in the target organ acts as a risk biomarker for the development of lung cancer. To verify this hypothesis, the aromatic/hydrophobic DNA adduct levels of non-tumorous adjacent lung tissues from 73 primary lung cancer patients and 33 non-cancer controls were evaluated by 32P-postlabelling assay. Wilcoxon rank sum test showed that DNA adduct levels in lung cancer patients (49.58+/-33.39 adducts/10(8) nucleotides) were significantly higher than those in non-cancer controls (18.00+/-15.33 adducts/10(8) nucleotides, P<0.001). The DNA adduct levels among lung cancer and non-cancer samples were not influenced by smoking behaviour and cigarette consumption. Our data also showed that the polymorphisms of cytochrome P4501A1 (CYP1A1) Msp1, glutathione S-transferase M1 (GSTM1) and the combination of both genetic polymorphisms were not related to the DNA adduct levels. Interestingly, positive association between CYP1A1 protein expression and DNA adduct levels was found when CYP1A1 protein expression in lung specimens from lung cancer patients was examined by immunohistochemistry. Multivariate linear regression analysis indicated that the DNA adduct level was not associated with gender, smoking behaviour, or genetic polymorphisms of CYP1A1 and GSTM1. Moreover, multivariate logistic regression analysis showed that persons with high DNA adduct levels (>48.66 adducts/10(8) nucleotides) had an approximately 25-fold risk of lung cancer compared with persons with low DNA adduct levels (</=48.66 adducts/10(8) nucleotides). In conclusion, DNA adduct levels in lung tissue may be a more reliable lung cancer susceptibility biomarker than DNA adduct levels in leucocytes. In addition, higher susceptibility to DNA damage in lung cancer patients may partly play a role in the development of lung cancer.

STAT signaling in the pathogenesis and treatment of leukemias

Leukemias continue to cause significant mortality in adults and children, and the use of standard cytotoxic chemotherapy has reached a therapeutic plateau. Thus, there is great interest in treatments directed against inappropriately activated cell signaling pathways which stimulate the uncontrolled growth of neoplastic cells. Increasing evidence suggests that the STAT signaling cascade may be one target of these therapies. Signal transducer and activator of transcription (STAT) proteins are critical in mediating the response of hematopoietic cells to a diverse spectrum of cytokines. Constitutive STAT activation is present in many malignancies and has been especially well characterized in acute and chronic leukemias. While STAT activation is a common characteristic of leukemias, the specific pattern of activated STATs and the manner by which STAT activation occurs vary with each disease. STAT tyrosine phosphorylation can occur through inappropriate Jak activation or by direct activation of an oncoprotein such as Bcr/Abl, and STAT serine phosphorylation may play an important role in leukemias as well. Thus, the STAT signaling pathway is an attractive target for therapeutic intervention, and strategies designed to inhibit STAT activation and STAT mediated gene transcription may play an important role in the next generation of anti-leukemia therapies. Oncogene (2000).

Synthesis and biological evaluation of 1,3-oxathiolane 5-azapyrimidine, 6-azapyrimidine, and fluorosubstituted 3-deazapyrimidine nucleosides

(2R,5S)-5-Amino-2-[2-(hydroxymethyl)-1,3-oxathiolan-5-yl]- 1,2,4-triazine-3(2H)-one (8) and (2R,5R)-5-amino-2-[2-(hydroxymethyl)-1,3-oxathiolan-5-yl]-1,2,4-tr iazine-3(2H)-one (9) have been synthesized via a multi-step procedure from 6-azauridine. (2R,5S)-4-Amino-1-[2-(hydroxymethyl)-1,3-oxathiolan-5-yl]-1,3, 5-triazine-2(1H)-one (11) and (2R,5R)-4-amino-1-[2-(hydroxymethyl)-1,3-oxathiolan-5-yl]- 1,3,5-triazine-2(1H)-one (12), and the fluorosubstituted 3-deazanucleosides (19-24) have been synthesized by the transglycosylation of (2R,5S)-1-[2-[[(tert-butyldiphenylsilyl) oxy]methyl]-1,3-oxathiolan-5-yl] cytosine (2) with silylated 5-azacytosine and the corresponding silylated fluorosubstituted 3-deazacytosines, respectively, in the presence of trimethylsilyl trifluoromethanesulfonate as the catalyst in anhydrous dichloroethane, followed by deprotection of the blocking groups. These compounds were tested in vitro for cytotoxicity against L1210, B16F10, and CCRF-CEM tumor cell lines and for antiviral activity against HIV-1 and HBV.

Time-course analysis of stretch reflexes in hemiparetic subjects using an on-line spasticity measurement system

Spasticity after a stroke is usually assessed in a score form by subjectively determining the resistance of a joint to an externally imposed passive movement. This work presents a spasticity measurement system for on-line quantifying the stretch reflex of paretic limbs. Four different constant stretch velocities in a ramp-and-hold mode are used to elicit the stretch reflex of the elbow joint in spastic subjects. The subjects are tested at supine position with the upper limb stretched towards the ground, in contrast with the horizontally stretched movement used in other studies. By subtracting the baseline torque, reflex torque measured at a selected low stretch velocity of 5 deg/sec, the influence of gravity torque and inertial in vertical stretching mode can be minimized. The averaged speed-dependent reflex torque (ASRT), defined as the measured torque deviated from the baseline torque, is used for quantifying the spastic hypertonia. Four subjects having incurred cerebrovascular accident (CVA) are recruited for time-course study in which the measurements are taken at 72 hours, one week, one month, three months, and six months after onset of stroke. During the development of spasticity, the changes of ASRT and velocity sensitivity of ASRT of the involved and the intact elbow joints are discussed.

Repeat transthoracic endoscopic sympathectomy for palmar and axillary hyperhidrosis

BACKGROUND

Patients undergoing an unsuccessful sympathectomy experience dryness on one hand and excessive sweating on the other. This is embarrassing for the patients, and resolution of both a previous failed sympathectomy and recurrent hyperhidrosis is important.

METHODS

From September 1995 to January 1998, 24 patients (11 men and 13 women; mean age, 28.2 years) underwent repeat transthoracic sympathectomy (TES). The repeat TES was performed with patients under general anesthesia using either a standard single-lumen endotracheal tube (12 patients) or a double-lumen endotracheal tube (12 patients). Ablation of T2 and T3 ganglia and any Kuntz fiber was performed in treating patients with palmar hyperhidrosis, and a similar procedure was performed on T3 and T4 ganglia for patients with axillary hyperhidrosis.

RESULTS

The reasons for failure of the previous TES were pleural adhesion (14/24), intact T2 ganglion (5/24), aberrant venous arch drainage to the superior vena cava (2/24), incomplete interruption of sympathetic nerve (2/24), and possible reinnervation (1/24). The mean operation time was 28 min (range, 18-72 min). In all, 23 patients had a satisfactory result, without recurrence of palmar or axillary hyperhidrosis. The mean follow-up time was 22 months (range, 5-30 months). The average hospital stay was 1.8 days. There was no surgical mortality.

CONCLUSION

Repeat TES is a safe and effective method for treating both an unsuccessful sympathectomy and recurrent palmar or axillary hyperhidrosis.

Pancreaticocolonic fistula after extensive corrosive injury from esophagus to jejunum

We report a case of extensive corrosive injury to the jejunum after ingestion of about 200 ml of hydrochloric acid as an attempted suicide. Subtotal esophagectomy, total gastroduodenectomy, segmental resection of the jejunum and partial pancreatectomy were performed in the first two operations. Forty-five days after surgery, the patient was well and discharged. Six months later, the patient underwent esophageal reconstruction surgery. During surgery, a pancreaticocolonic fistula between the head of the pancreas and the transverse colon was found. The esophageal reconstruction using the transverse colon was performed via the retrosternal route.

Esophageal tuberculosis: a rare presentation with massive hematemesis

A 43-year-old female presented with massive hematemesis. Esophagoscopy showed an ulcer 22 to 25 cm from the incisor with active bleeding. A thoracotomy and primary closure of the ulcer was performed. Massive hematemesis recurred 8 days later, resulting in hypovolemic shock. The thoracic esophagus was resected and histological examination showed granuloma with central caseous necrosis. Combined chemotherapy was given for 10 months. At 6 months after the subtotal esophagectomy, the esophagus was reconstructed using the right-side colon.

Transthoracic endoscopic sympathectomy in the treatment of palmar hyperhidrosis--with emphasis on perioperative management (1,360 case analyses)

BACKGROUND

Primary palmar hyperhidrosis (PH) is very common, and can be disabling. Various surgical methods for endoscopic sympathectomy have been advocated. We present a simple and effective method of treating PH by means of transthoracic endoscopic sympathectomy (TES).

METHODS

From July 1994 to May 1998, a total of 1,360 patients with hyperhidrosis palmaris underwent TES. There were 544 males and 816 females with a mean age of 23.1 years old (range, 5 to 60 years). All patients were placed in a half-sitting position under single-lumen intubational anesthesia. We performed the ablation of the T2 ganglion using either a 6- or 8-mm, 0-degree thoracoscope (Karl Storz Company, Germany)

RESULTS

In these 1,360 patients, 2,715 sympathectomies were performed. TES was usually accomplished within 15 min. Surgical complications were minimal: six cases of pneumothorax (0.44%), four cases of segmental collapse of lung (0.29%), and two wound infections (0.15%). There was no surgical mortality. The mean postoperative follow-up period was 27.8 months. A total of 1,292 patients (95%) had highly satisfactory results, although 1,140 patients (84%) have developed compensatory sweating of the trunk and lower limbs. The affected area was the axillae, back, abdomen, lower limbs (16%, 82%, 52%, and 78%, respectively). The recurrence rates of PH were 0.4% in the first year, 0.6% in the second year, and 1.1% in the third year.

CONCLUSIONS

TES is a simple, safe, and effective method of treating PH.

Interleukin-1 beta in oral submucous fibrosis, verrucous hyperplasia and squamous cell carcinoma tissues

Interleukin-1 beta (IL-1 beta) has been proven to be a multi-effect mediator of inflammation including in the promotion of inflammatory cells to move from blood to inflamed tissues, the regulation of the synthesis and decomposition of extra-cellular matrix, and indirectly in causing bone resorption and inhibition of bone growth. In this study, the amounts of IL-1 beta in the biopsied specimens of normal oral mucosa, oral submucous fibrosis (OSF), oral squamous cell carcinoma (OSCC), and verrucous hyperplasia (VerH) were quantified by ELISA. The results showed that the amounts of IL-1 beta (pg per mg tissue, mean +/- SD) in normal oral mucosa, OSF, OSCC, and VerH were 1.07 +/- 0.53, 0.76 +/- 0.56, 4.37 +/- 0.87 and 3.97 +/- 1.93 respectively. There were no significant differences (p > 0.05, Mann-Whitney U Test) between the amounts of IL-1 beta in normal oral mucosa and OSF, and between VerH and OSCC. However, a significant difference in IL-1 beta level was found (p < 0.001) between normal oral mucosa and OSCC or VerH. Immunohistochemistry staining technique using antibody against IL-1 beta showed positive staining in hyperplastic epithelium (VerH) and tumor cells of OSCC. These results might suggest a correlation between the amounts of IL-1 beta in oral precancerous and cancerous lesions and cell transformation. On the other hand, the amount of IL-1 beta did not change significantly as OSF progressed. Thus, IL-1 beta levels may not be useful to gauge the seriousness of fibrosis, but the gradual increase in IL-1 beta level from normal oral mucosa through VerH to OSCC suggests that IL-1 beta may play an important role in oral carcinogenesis.

Transthoracic endoscopic sympathectomy for palmar hyperhidrosis in children and adolescents: analysis of 350 cases

Primary palmar hyperhidrosis (PH) often commences in childhood and adolescence and can be a disabling condition. There are few reports regarding endoscopic sympathectomy for PH in children and adolescents. Therefore, I present our experience with transthoracic endoscopic sympathectomy (TES) in treating PH in children and adolescents. From July 1994 to March 1998, a total of 350 patients underwent TES. There were 93 males and 257 females with a mean age of 12.9 years (range 5-17 years). All patients were placed in a half-sitting position under single-lumen intubated anesthesia. We performed ablation of the T2 ganglion using either a 6- or an 8-mm 0 degree thoracoscope (Karl Storz Company, Germany) via one 0.8-cm incision just below each axilla. Among these 350 patients, 699 sympathectomies were performed. Usually, TES was accomplished within 15 minutes (range 7-20 minutes). The surgical complications were minimal: one pneumothorax and one segmental lung collapse. There were no surgical deaths. With a mean postoperative follow-up period of 25 months (range 5-44 months), the result of TES was highly satisfactory in 331 patients (94.6%), although 301 patients (86%) developed compensatory sweating of the trunk and lower limbs, the distribution being the axillae (12%), back (86%), abdomen (48%), or lower limbs (78%). The recurrence rates of palmar hyperhidrosis were 0.6% in the first year, 1.1% in the second year, and 1.7% in the third year. Transthoracic endoscopic sympathectomy is a safe and effective method for treating PH in children and adolescents.

Multielectrode surface EMG for noninvasive estimation of motor unit size

To noninvasively estimate the motor unit size, we present a novel surface electromyographic (EMG) measurement system consisting of a surface multielectrode with four-pin electrodes and a pair of surface-disk electrodes. Surface motor unit action potentials (MUAPs) were recorded with the multielectrode, in the so-called multielectrode surface EMG (MSEMG), which was spatially filtered to localize the sensing area and reduce the noise. In addition, a modified decomposition algorithm, considering the geometrical configuration of the multielectrode, was designed to identify the individual MUAPs in the measured MSEMG. The identified MUAP was subsequently used as the triggering source for the EMG signals recorded by the surface-disk electrodes. From a pool of 34 subjects with neuromuscular diseases and 14 normal subjects, the median amplitudes of surface-disk EMG after spike-triggered averaging, called MSEMG-MUAP, correlated well (r = 0.82, P < 0.0001) with those of macro EMG. Moreover, the MSEMG-MUAP recording during a ramp force contraction exhibited the common size principle phenomenon during motor unit recruitment. The results of this study demonstrate that the MSEMG-MUAP measurement is a feasible approach for estimating the motor unit size from the skin surface.

Transient magnetic resonance without RF pulses: fast field switching

An unusual strategy for performing magnetic resonance experiments is demonstrated. Instead of employing conventional radiofrequency transmitter fields to perturb spin state populations away from equilibrium, as is the basis of most magnetic resonance spectrometers today, technological advances now make possible fast switching of the magnetic field orientation to achieve the same effect. This is demonstrated with an electron spin resonance experiment where the magnetic field is switched 90 degrees nonadiabatically with a dead time of a few tens of nanoseconds and an electron free induction decay observed.

Sensitivity studies of AutoPap System Location-Guided Screening of cervical-vaginal cytologic smears

OBJECTIVE

To present the results of a study that assessed the efficacy of a cervical cytology screening method utilizing the AutoPap System with Location-Guided Screening (AutoPap LGS) software for detecting abnormal Papanicolaou smear slides.

STUDY DESIGN

Two hundred cases of abnormal cervical and vaginal smears were selected from the recent archives of the Taipei Institute of Pathology. For each abnormal slide, a matched "within normal limit" slide was included in the study. The slides were processed on the AutoPap Primary Screening System to select slides for Review or No Review and identify areas of the Review slides for human review and diagnosis (AutoPap LGS). The effectiveness of AutoPap LGS for detecting abnormal Papanicolaou smear slides was evaluated at multiple No Review rates.

RESULTS

The AutoPap LGS demonstrated statistically superior sensitivity over current laboratory practice for the identification of abnormal slides. Assessing the potential benefit of the AutoPap LGS using a projection method, it is expected that the AutoPap LGS would detect an additional 52 low grade squamous intraepithelial lesion and 13 high grade squamous intraepithelial lesion cases missed by current laboratory practice in a population of 2,860 cases.

CONCLUSION

The effectiveness of AutoPap LGS was demonstrated by its statistically superior performance in the detection of missed abnormal slides as compared to current laboratory practice at the Taipei Institute of Pathology.

Dynamic nuclear polarization in pulsed ENDOR experiments

Properly prepared pulse sequences of microwave and radio frequency have been employed to investigate the effect of polarization transfer from the polarized photo excited triplet state of pentacene in p-terphenyl crystals to the surrounding protons in pulsed ENDOR experiments. The ENDOR signal, measured as the change of electron spin echo (ESE) amplitude, is affected by the mode of RF pulses. When B0 parallelx (the long molecular axis), the ESE amplitude of the high-field transition of the triplet state changes from the maximum positive to zero with a pi RF pulse, and to the maximum negative with a 2pi pulse, while that of the low-field transition changes from nearly zero to the maximum negative as the RF pulse width increases. The effect is attributed to the strong electron spin polarization produced in the creation of the photoexcited triplet state and the subsequent efficient electron- nuclear polarization transfer process.

Transthoracic endoscopic sympathectomy for palmar and axillary hyperhidrosis in children and adolescents

Primary hyperhidrosis (PH) often starts in childhood and adolescence and can be a troublesome condition. In Taiwan, there is a high incidence in childhood (1.6%-2.0%) and adolescence (2.2%-2.6%). There are few reports regarding transthoracic endoscopic sympathectomy (TES) for PH in children and adolescents. From July 1994 to April 1998, a total of 438 patients underwent TES. There were 174 males and 264 females with a mean age of 14.2 years (range 5-17 years). All patients were placed in a semi-sitting position under single-lumen intubation anesthesia. We performed ablation of the T2 ganglion and any Kuntz fibers in 350 patients with palmar hyperhidrosis and a similar procedure on the T2 and T3 ganglia in 88 patients with palmar and axillary hyperhidrosis using either a 6- or 8-mm thoracoscope via one 0.8-cm incision just below each axilla. In the 438 patients, 875 sympathectomies were performed. There was 1 technical failure due to severe pleural adhesions. TES was usually accomplished within 15 min (range 7-20 min). All except 5 patients were discharged within 4 h after operation. The surgical complication rate was minimal: 1 pneumothorax (0.23%) and 2 segmental lung collapses (0.46%). There was no surgical mortality. The mean postoperative follow-up period was 25.2 months (range 4-45 months). The result was highly satisfactory in 408 patients (93.2%), although 377 (86%) developed compensatory sweating of the trunk and lower limbs, the distribution affecting the back (86%), abdomen (48%), lower limbs (78%), and soles (1.4%). The recurrence rate of palmar hyperhidrosis was 0.6% in the 1st, 1.1% in the 2nd, and 1.7% in the 3rd year. TES is thus a safe and effective method for treating palmar and axillary hyperhidrosis in children and adolescents.

Synthesis of 2'-methylene-substituted 5-azapyrimidine, 6-azapyrimidine, and 3-deazaguanine nucleoside analogues as potential antitumor/antiviral agents

2'-Deoxy-2'-methylene-6-azauridine (5) and 2'-deoxy-2'-methylene-6-azacytidine (8) have been synthesized via a multi-step procedure from 6-azauridine. 2'-Deoxy-2'-methylene-5-azacytidine (14a) and 2'-deoxy-2'-methylene-3-deazaguanosine (19a) and their corresponding alpha-anomers (14b and 19b) have been synthesized by the transglycosylation of 3',5'-O-(1,1,3,3- tetraisopropyldisiloxane-1,3-diyl)-2'-deoxy-2'-methyleneu ridine (12) with silylated 5-azacytosine and silylated N2-palmitoyl-3-deazaguanine, respectively, in the presence of trimethylsilyl trifluoromethanesulfonate as the catalyst in anhydrous dichloroethane, followed by separation of the isomers and deprotection of the blocking groups. These compounds were tested for cytotoxicity against B16F10, L1210, and CCRF-CEM tumor cell lines and for antiviral activity against HIV-1, HSV-1, and HSV-2.

Electron paramagnetic resonance detection of free tyrosyl radical generated by myeloperoxidase, lactoperoxidase, and horseradish peroxidase

Phagocytes secrete the heme protein myeloperoxidase, which is present and active in human atherosclerotic tissue. These cells also generate hydrogen peroxide (H2O2), thereby allowing myeloperoxidase to generate a range of oxidizing intermediates and stable end products. When this system acts on L-tyrosine in vitro, it forms o, o'-dityrosine, which is enriched in atherosclerotic lesions. Myeloperoxidase, therefore, may oxidize artery wall proteins in vivo, cross-linking their L-tyrosine residues. In these studies, we used electron paramagnetic resonance (EPR) spectroscopy to identify an oxidizing intermediate in this reaction pathway and in parallel reactions catalyzed by horseradish peroxidase and lactoperoxidase. Using an EPR flow system to rapidly mix and examine solutions containing horseradish peroxidase, H2O2, and L-tyrosine, we detected free tyrosyl radical (a2,6H = 6.3 G, a3,5H = 1.6 G, and abetaH = 15. 0 G). We then used spin trapping techniques with 2-methyl-2-nitrosopropane (MNP) to further identify this intermediate. The resulting three-line spectrum (aN = 15.6 G) was consistent with an MNP/tyrosyl radical spin adduct. Additional MNP spin trapping studies with ring-labeled L-[13C6]tyrosine yielded a characteristic eight-line EPR spectrum (aN = 15.6 G, a13C (2) = 8.0 G, a13C (1) = 7.1 G, a13C (1) = 1.3 G), indicating that the MNP adduct resulted from trapping a carbon-centered radical located on the aromatic ring of L-tyrosine. This same eight-line spectrum was observed when human myeloperoxidase or bovine lactoperoxidase was substituted for horseradish peroxidase. Furthermore, a partially immobilized MNP/tyrosyl radical spin adduct was detected when we exposed a synthetic polypeptide composed of glutamate and L-tyrosine residues to the myeloperoxidase-H2O2-L-tyrosine system. The broadened EPR signal resulting from this MNP/polypeptide adduct was greatly narrowed by proteolytic digestion with Pronase, confirming that the initial spin-trapped radical was protein-bound. Collectively, these results indicate that peroxidases use H2O2 to convert L-tyrosine to free tyrosyl radical. They also support the idea that free tyrosyl radical initiates cross-linking of L-tyrosine residues in proteins. We suggest that this pathway may play an important role in protein and lipid oxidation at sites of inflammation and in atherosclerotic lesions.

Role of gp55 in restoring the sensitivity of Friend murine erythroleukemia cells to erythropoietin by exposure to dimethyl sulfoxide

Although Friend murine erythroleukemia (MEL) cells express the erythropoietin receptor (EpoR), they are insensitive to erythropoietin (Epo). The nonresponsiveness to Epo presumably results from gp55, the product of the env gene encoded by the Friend spleen focus-forming virus (F-SFFV), acting as a pseudoligand and constitutively activating the receptor. Dimethyl sulfoxide (DMSO) induced the differentiation of MEL cells and partially restored responsiveness to Epo, with both increased proliferation and further hemoglobin synthesis. Treatment of MEL cells with DMSO caused a decrease in the cellular content of gp55 as measured by Western analysis and an increase in the level of the EpoR as measured by [125I]Epo binding. These changes were produced at least in part at the transcriptional level, because DMSO treatment caused a decrease and an increase in the levels of the mRNAs for gp55 and EpoR, respectively. To ascertain the role of gp55 in the restoration of the sensitivity of MEL cells to Epo by exposure to DMSO, expression vectors containing gp55 DNA in the sense and antisense orientations were transfected into MEL cells to increase or decrease, respectively, the amount of cellular gp55. An increase in the level of gp55 interfered with the ability of DMSO to restore sensitivity to Epo, whereas a decrease in the level of gp55 increased the Epo-sensitizing effects of DMSO. [125I]Epo was chemically cross-linked to a component with a calculated molecular weight of 65 kDa. DMSO treatment caused an increase in the level of [125I]Epo cross-linking. The protein cross-linked to Epo was immunoprecipitated with anti-EpoR serum but not with anti-gp55 serum, suggesting that Epo was cross-linked to its receptor. The finding of a decrease in the cellular content of gp55, an increase in the level of the EpoR, and an increase in the formation of the Epo/EpoR complex is consistent with the acquisition of sensitivity to Epo by MEL cells following treatment with DMSO.

Motor end-plate jitter in myasthenia gravis at different firing rates

Twenty patients with generalized myasthenia gravis (MG) were studied to assess firing rate-dependent changes in end-plate jitter. Stimulated single-fiber electromyography (EMG) was performed in the extensor digitorum communis muscles at stimulation frequencies of 1, 2, 5, and 10 Hz for all the sampled fibers and at 20 Hz for a few ones. In all 137 end-plates were obtained, of which 43 showed blocking. Statistical analysis demonstrated significant increases in jitter and the blocking rate from 1 to 2 and 2 to 5 Hz, whereas there were decreases from 5 to 10 and 10 to 20 Hz. Further analysis showed that the decrement in jitter from 5 to 10 Hz was greater in end-plates with preexisting low safety factors. In contrast, even though the safety factor of long-duration MG end-plates was lower than that of the short-duration group, the decrement in jitter was insignificant in the long-duration MG end-plates. These results suggest that the intratetanic facilitation effect begins at 10 Hz and is more prominent in end-plates with a preexisting low safety factor. Long-lasting MG, however, eliminates this effect.

Characterization of the relationship between motor end-plate jitter and the safety factor

A mathematical model developed for a personal computer was used to simulate the jitter phenomenon in neuromuscular transmission in order to characterize the relationship between jitter and the safety factor. Four models of normal and abnormal neuromuscular transmission were investigated. In a human experiment, the mean consecutive difference (MCD) values for stimulated single-fiber electromyography at firing rates of 1, 2, 5, and 10 Hz were measured in 137 motor end-plates of myasthenic patients. Results of the computer simulations show that the relationship between jitter and the safety factor is exponential like. Variations in jitter are most prominent in end-plates with low safety factors. This relationship agrees with results of human end-plate studies. Changes in the MCD values caused by presynaptic depression or facilitation are linearly correlated to the initial jitter, whereas the logarithmic values of MCD are not. It is very important to keep in mind this nonlinear relationship when relating single-fiber jitter to the safety factor.

Stimulated single-fiber electromyography in the rat

We constructed an animal model of stimulated single-fiber electromyography (SFEMG) by testing Wistar rats under anesthesia. Stimuli of 1 Hz were applied to the sciatic nerve through an insulated monopolar needle electrode. Single-fiber action potentials were acquired from the gastrocnemius muscle. Jitter was assessed by the mean consecutive difference (MCD). Eighty-seven fibers were obtained from 12 rats. Their MCDs ranged from 2 to 72 micros (17.7+/-13.4). Seven of these values were less than or equal to 5 micros, and three exceeded 50 micros. Neuromuscular blocking agents injected into some of the rats induced considerable increases in jitter and blocking. A rat with one fiber with an MCD less than 5 micros also received an injection of curare. The jitter showed the same pattern of increment, evidence that the small jitter was not attributable to direct muscle stimulation. These results show that SFEMG can be used on rats. In addition, jitter reflects the changes in motor end-plate function. The findings also suggest the presence of an extremely high safety factor in rat neuromuscular junctions.

Norepinephrine transmitter metabolite generates free radicals and activates mitochondrial permeability transition: a mechanism for DOPEGAL-induced apoptosis

3,4-Dihydroxyphenylglycolaldehyde (DOPEGAL) is the monoamine oxidase A metabolite of norepinephrine (NE) and epinephrine. DOPEGAL, but neither NE nor its other metabolites induces apoptosis in differentiated PC-12 cells by an unknown mechanism. To study the mechanism of DOPEGAL-induced apoptosis, we tested DOPEGAL and NE for their capacity to generate free radicals and to induce mitochondrial permeability transition (PT). Results show that DOPEGAL but not NE forms reactive free radical intermediates under oxidative stress and enhances Ca2+-mediated induction of the mitochondrial PT. Linkage of these events to apoptosis is described. Implications for degenerative diseases are discussed.

Revised hydrolysis constants for thallium(I) and thallium(III) and the environmental implications

The hydrolysis constants for Tl(I) and Tl(III) have been determined by combining potentiometric measurement with the PKAS computer program. The log hydrolysis constants (Khi) for Tl(I)(OH)i-1i + H2O<==>Tl(I) (OH)i1-i + H+ have been determined to be -11.7, and those for Tl(III)(OH)i-1(4-i) + H2O<==>Tl(III)(OH)i3-i + H+ are -2.69, -6.36, -7.42, and -8.78, respectively. The corresponding stepwise association constant for monovalent thallium is 10(2.3) for Tl(OH)aq, and those for trivalent thallium are 10(11.31) for Tl(OH)2+, 10(7.64) for Tl(OH)2+, 10(6.58) for Tl(OH)3aq, and 10(5.22) for Tl(OH)4-. The solubility product (Ksp) for solid Tl(OH)3,Solid has been redetermined to be 10(-45.2), implying that it is one of the least soluble among metal hydroxides. Revised fields of predominance of Tl(I) and Tl(III) hydroxides in aquatic environment are described, and the importance of Tl(III)/Tl(I) redox couple in the cycling of thallium is discussed.

Carboxyfullerenes as neuroprotective agents

Two regioisomers with C3 or D3 symmetry of water-soluble carboxylic acid C60 derivatives, containing three malonic acid groups per molecule, were synthesized and found to be equipotent free radical scavengers in solution as assessed by EPR analysis. Both compounds also inhibited the excitotoxic death of cultured cortical neurons induced by exposure to N-methyl-D-aspartate (NMDA), alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), or oxygen-glucose deprivation, but the C3 regioisomer was more effective than the D3 regioisomer, possibly reflecting its polar nature and attendant greater ability to enter lipid membranes. At 100 microM, the C3 derivative fully blocked even rapidly triggered, NMDA receptor-mediated toxicity, a form of toxicity with limited sensitivity to all other classes of free radical scavengers we have tested. The C3 derivative also reduced apoptotic neuronal death induced by either serum deprivation or exposure to Abeta1-42 protein. Furthermore, continuous infusion of the C3 derivative in a transgenic mouse carrying the human mutant (G93A) superoxide dismutase gene responsible for a form of familial amyotrophic lateral sclerosis, delayed both death and functional deterioration. These data suggest that polar carboxylic acid C60 derivatives may have attractive therapeutic properties in several acute or chronic neurodegenerative diseases.