Selective inactivation of glyceraldehyde-3-phosphate dehydrogenase by vinyl sulfones

Incubation of glyceraldehyde-3-phosphate dehydrogenase with vinyl sulfones resulted in a pseudo first-order loss of enzyme activity. The selective inactivation of the enzyme by vinyl sulfones is suggested from the structural requirement analysis and the enzyme susceptibility test. The enzyme inactivation was strongly reduced in the presence of NAD or glyceraldehyde-3-phosphate, and the prior treatment of the enzyme with 5,5'-dithio-bis-(2-nitrobenzoic acid) prevented the enzyme from the inactivation by vinyl sulfones (> or = 90%). Moreover, the early rapid phase of inactivation was much more responsive to L-cysteine reactivation, compared with the slower phase. Based on these results, it is proposed that vinyl sulfones inactivate the enzyme by inducing the oxidation of cysteine residue and/or covalent binding to cysteine residue in active site.     

Electroconvulsive shock does not induce c-fos and junB, but TIS1 and TIS8/zif-268, in neonatal rat hippocampus

Insular neurons responsive to baroreceptor challenge have been identified in the rat, but not previously in primates. Characterization of baroreceptor-related neurons was performed in 15 anesthetized monkeys (Macaca fascicularis) using extracellular single-unit recording techniques. 131 units were investigated within the insula and surrounding regions. Based on their responses to phenylephrine hydrochloride (PE) and sodium nitroprusside (SNP), three types of units were distinguished: 35/131 (27%) sympathoexcitatory (SE), 12/131 (9%) sympathoinhibitory (SI) and 84 (64%) null units. More baroreceptive units were found within the insula (38/73, 52%) than in surrounding areas (9/58, 16%) (p < 0.001). Lateralization was indicated with more baroreceptive units being encountered within the right insula (28/44, 64%) than the left (10/29, 34%) (p = 0.02). The majority of the responsive units were located within the dysgranular and granular insula in layers II, III and V/VI. These data suggest that cardiovascular representation may occur in the primate insula as has been shown in other species.     

Regulation of presynaptic NMDA responses by external and intracellular pH changes at developing neuromuscular synapses

NMDA receptors play important roles in synaptic plasticity and neuronal development. The functions of NMDA receptors are modulated by many endogenous substances, such as external pH (pHe), as well as second messenger systems. In the present study, the nerve-muscle cocultures of Xenopus embryos were used to investigate the effects of both external and intracellular pH (pHi) changes on the functional responses of presynaptic NMDA receptors. Spontaneous synaptic currents (SSCs) were recorded from innervated myocyte using whole-cell recordings. Local perfusion of NMDA at synaptic regions increased the SSC frequency via the activation of presynaptic NMDA receptors. A decrease in pHe from 7.6 to 6.6 reduced NMDA responses to 23% of the control, and an increase in pHe from 7.6 to 8.6 potentiated the NMDA responses in increasing SSC frequency. The effect of NMDA on intracellular Ca2+ concentration ([Ca2+]i) was also affected by pHe changes: external acidification inhibited and alkalinization potentiated [Ca2+]i increases induced by NMDA. Intracellular pH changes of single soma were measured by ratio fluorometric method using 2,7-bis (carboxyethyl)-5, 6-carboxyfluorescein (BCECF). Cytosolic acidification was used in which NaCl in Ringer's solution was replaced with weak organic acids. Acetate and propionate but not methylsulfate substitution caused intracellular acidification and potentiated NMDA responses in increasing SSC frequency, intracellular free Ca2+ concentration, and NMDA-induced currents. On the other hand, cytosolic alkalinization with NH4Cl did not significantly affect these NMDA responses. These results suggest that the functions of NMDA receptors are modulated by both pHe and pHi changes, which may occur in some physiological or pathological conditions.     

Rat testicular extracellular superoxide dismutase: its purification, cellular distribution, and regulation

Rehabilitative measures for stroke are not generally based on basic neurobiological principles, despite evidence from animal models that certain anatomical and pharmacological changes correlate with recovery. In this report, we use functional magnetic resonance imaging (fMRI) to study in vivo human brain reorganization in a right handed patient with an acquired reading disorder from stroke. With phonological dyslexia, her whole-word (lexical) reading approach included inability to read nonwords and poor reading of function words. Following therapy, she was able to read nonwords and function words, and preferred a decompositional (sub-lexical) strategy in general. fMRI was performed during a reading task before and after treatment. Prior to therapy, her main focus of brain activation was in the left angular gyrus (area 39). After therapy, it was instead in the left lingual gyrus (area 18). This result suggests first that it is possible to alter brain physiology with therapy for acquired language disorders, and second, that two reading strategies commonly used in normal reading use distinct neural circuits, possibly reconciling several conflicting neuroimaging studies of reading.     

Identification of clustered microcalcifications on digitized mammograms using morphology and topography-based computer-aided detection schemes. A preliminary experiment

RATIONALE AND OBJECTIVES: A mathematical morphology-based computer-aided detection (CAD) scheme for the identification of clustered microcalcifications was developed and tested. The potential for improving either sensitivity or specificity by combining the results with those previously reported was investigated. METHODS: The CAD scheme presented here is based on mathematical morphology and a series of simple rule-based criteria for the identification of clustered microcalcifications. A database of 105 digitized mammograms was used for training and rule setting of the scheme. A test set of 191 digitized mammograms was used to evaluate its performance. The same test set had been used to evaluate a multilayer, topography-based scheme. The results obtained by the two schemes were then combined using logical OR and AND operations. RESULTS: The morphology-based and topography-based CAD schemes performed at sensitivities of 82.9% and 89.5%, with false-positive detection rates of 1.3 and 0.4 per image, respectively. A logical OR operation resulted in 95.4% sensitivity. An AND operation achieved 76.2% sensitivity, with no false identifications on 93% of images. CONCLUSIONS: By combining the results of the morphology-based and the topography-based schemes, either sensitivity or specificity can be improved.     

Fixation of osteotomies using bioabsorbable screws in the canine femur

The purpose of this study was to compare the healing properties of femoral osteotomies fixed by bioabsorbable screws (20:80 polyglycolic copolylactic acid copolymer) to standard stainless steel screws of a similar design in a dog femoral model. Two osteotomies were used, the trephine osteotomy (10 mm diameter) in the metaphyseal lateral femoral condyle and in the femoral diaphysis, and a unilateral osteotomy in the lateral femoral condyle. Two months after the trephine osteotomies, the femurs that contained the polymer screws were not significantly different in mechanical strength from the femurs treated with the stainless steel screws, either in the diaphyseal or metaphyseal model. There was no histological difference in bone healing between the metallic and polymer screws for all periods (2, 9, and 17 months). There was no adverse inflammatory response to the polymeric or metallic screws. By month 17, the polymer screws were resorbed completely. All the diaphyseal screw tracks had healed with bone and areas of remodeling were evident in two specimens. For the femoral condyle osteotomy model at 2 months, the polymer screws were present and intact, and all osteotomies healed with no evidence of inflammation. By 9 months, only one specimen had polymeric material left in the screw track. At 15 months, the screw tracks still were present but no evidence of any polymer remained. The tracks were filled with fibrous and adipose connective tissue. All osteotomies stabilized with either bioabsorbable polymer screws or stainless steel screws did heal satisfactorily without any complications, inflammation, or osteolysis. The polyglycolic polylactic acid copolymer may have a clinical role as a bioabsorbable material without the concerns for the osteolysis, foreign body reaction, and sterile abscess formation that have occurred with bioabsorbable fixation methods in the past.