Total DNA 5-methylcytosine level of rice calli derived from protoplasts is independent of regeneration ability

To study the roles of m⁵C in the differentiation of rice calli derived from protoplasts (protoclones), the m⁵C level of the total DNA was analyzed using the³²P post-labeling method. The level of m⁵C in regenerable and nonregenerable protoclones was similar, as was in calli and leaves of plants regenerated from the same protoclones. Treatment with 0.5 mM 5-azacytidine caused significant reduction of the level of m⁵C and of the regeneration frequency of callus. Significantly increased m⁵C levels were observed during prolonged culture.     

Anatomy of pharynx in patients with obstructive sleep apnea and in normal subjects

Isono, Shiroh, John E Remmers, Atsuko Tanaka, Yasuhide Sho,Jiro Sato, and Takashi Nishino. Anatomy of pharynx in patients with obstructive sleep apnea and in normal subjects.J. Appl. Physiol. 82(4):1319-1326, 1997.Anatomic abnormalities of the pharynx arethought to play a role in the pathogenesis of obstructive sleep apnea(OSA), but their contribution has never been conclusively proven. Thepresent study tested this anatomic hypothesis by comparing themechanics of the paralyzed pharynx in OSA patients and in normalsubjects. According to evaluation of sleep-disordered breathing (SDB)by nocturnal oximetry, subjects were divided into three groups: normalgroup (n = 17), SDB-1(n = 18), and SDB-2(n = 22). The static pressure-arearelationship of the passive pharynx was quantified under generalanesthesia with complete paralysis. Age and body mass index werematched among the three groups. The site of the primary closure was thevelopharynx in 49 subjects and the oropharynx in only 8 subjects.Distribution of the location of the primary closure did not differamong the groups. Closing pressure(PC) of the velopharynx forSDB-1 and SDB-2 groups (0.90 ± 1.34 and 2.78 ± 2.78 cmH₂O, respectively) wassignificantly higher than that for the normal group (3.77 ± 3.44 cmH₂O;P < 0.01). Maximal velopharyngealarea for the normal group (2.10 ± 0.85 cm²) was significantly greaterthan for SDB-1 and SDB-2 groups (1.15 ± 0.46 and 1.06 ± 0.75 cm², respectively). Theshape of the pressure-area curve for the velopharynx differed betweennormal subjects and patients with SDB, being steeper in slope nearPC in patients with SDB.Multivariate analysis of mechanical parameters and oxygen desaturationindex (ODI) revealed that velopharyngealPC was the only variable highly correlated with ODI. VelopharyngealPC was associated withoropharyngeal PC, suggestingmechanical interdependence of these segments. We conclude that thepassive pharynx is more narrow and collapsible in sleep-apneic patientsthan in matched controls and that velopharyngeal PC is the principal correlate ofthe frequency of nocturnal desaturations.

     

Post-ischemic administration of the acetylcholinesterase inhibitor ENA-713 prevents delayed neuronal death in the gerbil hippocampus

We examined by morphological methodology the effect of (S)-N-ethyl-3-[(1-dimethyl-amino)ethyl]-N-methyl-phenylcarbamate hydrogentartrate (ENA-713), an acetylcholinesterase (AChE) inhibitor, on ischemia-induced neuronal death in the gerbil hippocampus due to a 5-min ligation of bilateral common carotid arteries after light ether anesthesia. Pyramidal cells had been decreased to 27% of sham-operated controls and the number of hypertrophic astrocytes expressing glial fibrillary acidic protein (GFAP) markedly increased in the hippocampal CA1 subfield 14 days after ischemia. However, post-ischemic administration of ENA-713 (three times 0.2 mg/kg, i.p.) significantly ameliorated this ischemia-induced decrease in the number of pyramidal cells by 47% of sham-operated controls, furthermore, it reduced the ischemia-induced accumulation of GFAP-positive astrocyte in the CA1 region. Together with previous results showing that ENA-713 protected against the ischemia-induced cholinergic abnormalities in the gerbil brain and improved cholinergic dysfunctions in the senescent rat brain, our present findings suggest that ENA-713 prove to be useful for treatment with senile dementia such as cerebrovascular dementia.     

Fluorogenic substrates for the enkephalin-degrading neutral endopeptidase (Enkephalinase)

Rat brain neutral endopeptidase ("Enkephalinase") was shown to hydrolyze a series of fluorogenic substrates of the general structure 2-aminobenzoyl-(amino acid)n- leucylalanylglycine -4- nitrobenzylamide . The hydrolysis of these substrates was competitively inhibited by Leu5-enkephalin, demonstrating that these are indeed substrates for the rat brain neutral endopeptidase. Cleavage of the fluorogenic substrates yielded leucylalanylglycine -4- nitrobenzylamide as a common product. In addition, a series of inhibitors previously shown to inhibit thermolysin-like enzymes inhibited the hydrolysis of both Leu5-enkephalin and the synthetic substrates. The results of this study (a) demonstrate that the enkephalin-degrading endopeptidase is similar in specificity to thermolysin, (b) provide a continuous sensitive assay system for the enzyme, and (c) point out the potential use of this substrate class for probing the specificity of the enzyme.     

The crystallization of mitochondrial cytochrome oxidase-cytochrome c complex

Conditions are described under which crystals are formed with equimolar complex of mitochondrial cytochrome oxidase and cytochrome c. Characteristic absorption bands of the solubilized crystals could be attributed to the cytochrome oxidase-cytochrome c complex with heme a:c ratio of 2:1. Activity of crystals shows more close heme-heme interaction between two cytochromes than that of the mixture.