Restoration of frequency-dependent depression of the H-reflex by passive exercise in spinal rats.

STUDY DESIGN: Hyper-reflexia, measured as a decrease of low frequency-dependent depression of the H-reflex, is known to occur in both humans and animals after spinal cord injury (SCI). Previous studies have shown that passive exercise for 3 months could be used to restore low frequency-dependent depression of the H-reflex after SCI. OBJECTIVE: To determine the effects of various periods of time on the ability of passive exercise to restore low frequency-dependent depression of the H-reflex. SETTING: Spinal Cord Injury Mobilization Program of the Center for Translational Neuroscience, the research arm of the Jackson T Stephens Spine and Neuroscience Institute, Little Rock, AR, USA. METHODS: Adult rats underwent complete spinal cord transection at the T10 level. The hindlimbs were passively exercised in different groups of rats for 1 h/day, 5 days/week for 15, 30, 45, 60, or 90 days, and low frequency-dependent depression of the H-reflex was tested. RESULTS: Statistically significant low frequency-dependent depression of the H-reflex was evident by 30 days of exercise, although numerical reductions were seen even at 15 days. There was a linear decrease in low frequency-dependent depression of the H-reflex with duration of passive exercise. CONCLUSIONS: Passive exercise can restore frequency-dependent depression of spinal reflexes in a time-dependent manner if used following complete spinal transection.

Improved synthesis and the crystal structure of methyl 4,6-dideoxy-4-(3-deoxy-L-glycero-tetronamido)-alpha-D-mannopyrano side, the methyl alpha-glycoside of the intracatenary repeating unit of the O-polysaccharide of Vibrio cholerae O:1.

The crude product of deamination of the commercially available L-homoserine was acetylated and the 2-O-acetyl-3-deoxy-L-glycero-tetronolactone (18) formed was used to N-acylate methyl perosaminide (methyl 4-amino-4,6-dideoxy-alpha-D-mannopyranoside, 12) and its 2,3-O-isopropylidene derivative. The major product isolated from the reaction was the crystalline methyl 4-(4-O-acetyl-3-deoxy-L-glycero-tetronamido)-4,6-dideoxy-alpha-D-+ ++mannopyranoside (1, 70-75%) resulting from acetyl group migration in the initially formed 2'-O-acetyl derivative. O-Deacetylation of 1 gave the title amide 2. Compound 2, obtained crystalline for the first time, was fully characterized, and its crystal structure was determined. Deoxytetronamido derivatives diastereomeric with 1 and 2, respectively, were obtained by the acylation of 12 with 2-O-acetyl-3-deoxy-D-glycero-tetronolactone (prepared from D-homoserine), and subsequent deacetylation. Structures of several byproducts of the reaction of 12 with 18 have been deduced from their spectral characteristics. Since these byproducts were various O-acetyl derivatives of 2, the title compound could be obtained in approximately 90% yield by deacetylating (Zemplén) the crude mixture of N-acylation products, followed by chromatography.