AMPA receptor activation and phosphatase inhibition affect neonatal rat respiratory rhythm generation

1. We investigated the role of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) receptors and their regulation in affecting respiratory-related neurones in a neonatal rat medullary slice that spontaneously generates respiratory-related rhythm and motor output in the hypoglossal (XII) nerve. 2. Bath application of the AMPA receptor antagonist 1-(4-aminophenyl)-4-methyl-7,8-methylenedioxy-5H-2, 3-benzodiazepine (GYKI) completely blocked XII nerve activity, as well as respiratory-related synaptic drives in neurones within the preBötzinger Complex (preBotC), site of rhythm generation in the slice. 3. Local application of GYKI to the preBötC blocked respiratory rhythm. Local application of AMPA to the preBötC increased rhythm frequency and depolarized respiratory-related neurones. 4. In the presence of tetrodotoxin (TTX), GYKI completely blocked the inward current induced by local application of AMPA, but not that induced by kainate. 5. Local application of okadaic acid, a membrane-permeable inhibitor of phosphatase 1 and 2A, to the preBotC increased the frequency of respiratory motor discharge. 6. Intracellular application of microcystin, a membrane-impermeable inhibitor of phosphatase 1 and 2A, enhanced endogenous inspiratory drive and exogenous AMPA-induced current (in the presence of TTX) in preBotC inspiratory neurones. Both the enhanced inspiratory drive and the increased AMPA-induced current were completely blocked by GYKI. 7. We suggest that AMPA receptor activation and AMPA receptor modulation by phosphorylation are crucial for the rhythm generation within the preBötC.

Ordering of ruthenium cluster carbonyls in mesoporous silica

The anionic ruthenium cluster carbonylates [Ru6C(CO)16]2- or [H2Ru10(CO)25]2- interspersed with bis(triphenylphosphino)iminium counterions (PPN+) are incorporated from solution into the pores of MCM-41 mesoporous silica (3 nanometers in diameter), where they form tightly packed arrays. These arrays were shown by high-resolution transmission electron microscopy, Fourier transform optical diffraction, and computer simulations to be well ordered both along and perpendicular to the axis of the cylindrical pores. In their denuded state produced by gentle thermolysis, the cluster carbonylates yield nanoparticles of ruthenium that are less well ordered than their assimilated precursors but show good activity as hydrogenation catalysts for hexene and cyclooctene. In both their as-prepared and denuded states, these encapsulated clusters are likely to exhibit interesting electronic and other properties.

Epitope analysis of the major reactive region of the 100-kd protein of PM-Scl autoantigen

OBJECTIVE

To localize the epitope(s) bound by anti-PM-Scl antibodies in the N-terminal half of the 100-kd protein, the major antigen of the PM-Scl complex.

METHODS

Investigations were performed by immunoblotting 20 anti-PM-Scl positive sera against bacterially expressed, polymerase chain reaction-derived deletion mutants of the S1 fragment (amino acids 11-437), enzyme-linked immunosorbent assay (ELISA) screening against synthesized serial octapeptides, and ELISA screening, with anti-PM-Scl positive sera, against a synthesized 21-amino acid peptide covering the active region.

RESULTS

Anti-PM-Scl positive sera retained full immunoblot activity with fragment 207-436 and most activity with fragment 11-241, but had markedly decreased activity against fragments 236-436 and 11-212, indicating a major epitope in the aa 207-241 region. Fusion proteins with smaller fragments localized this activity between aa 226 and aa 246. Of 42 anti-S1-positive, anti-PM-Scl positive sera tested by ELISA against a synthetic peptide of this region, 36 were definitely positive, 4 borderline, and 2 negative. Similar activity was seen with a peptide from which proline 228 was deleted. Three additional epitope areas were found in S1, but each reacted with only a few sera. Anti-PMScl positive sera did not react with any octapeptide spanning the major epitope area (aa 207-246).

CONCLUSION

The main immunoblot epitope of the PM-Scl 100-kd protein is within a central area of 21 aa (aa 226-246), but is longer than the usual linear epitope. This peptide may be useful in patient testing. Three minor epitopes in S1 may also be recognized by some sera.

Molecular analysis of a major antigenic region of the 240-kD protein of Mi-2 autoantigen

Anti-Mi-2 autoantibody is strongly associated with dermatomyositis and found in sera of 20% of patients. Mi-2 antigen contains at least eight components and previous evidence suggested that the 240-kD protein was the antigenic component for at least some sera. In this study, anti-M-2 patient sera were used to screen human thymocyte and HeLa cell lambda gt11 expression libraries, and two clones from each had plaques specifically reactive with anti-Mi-2 sera. Studies with affinity-purified antibody supported the identification of the clones. All of 44 anti-Mi-2 sera reacted with the plaques, but none of 44 control sera reacted significantly. The cDNAs were identical, and full sequencing of one revealed an open reading frame spanning a 1,054-bp insert. Rescreening the library with the cDNA yielded a 1,589-bp cDNA that continued the open reading frame. The Mi-2 cDNA hybridized to a single 7.5-8.0 kb mRNA of HeLa cells, by Northern blot. Rabbit antiserum directed at a portion of the cDNA product reacted with HeLa 240-kD Mi-2 protein. The sequence was notable for four potential zinc-fingers and several charged regions. The protein encoded by the cDNA produced in vitro reacted with only one of five of the Mi-2 sera. These findings indicate that the Mi-2 240 kD is a novel protein that is antigenic for all Mi-2 sera, and strongly suggests that a major common epitope is conformational in nature.

Primary structure and functional expression of human Glycyl-tRNA synthetase, an autoantigen in myositis

Two identical cDNAs encoding human glycyl-tRNA synthetase were isolated from K562 and HEL cell lambda gt11 libraries by screening with "anti-EJ" autoantibodies from a patient with dermatomyositis, previously shown to specifically inhibit this enzyme. The sequenced cDNA had 2,385 base pairs, with a predicted protein of 685 amino acids and M(r) 77,500. The antigen reactive with anti-EJ was immunoaffinity-purified from HeLa cells, and two proteolytic peptides matched areas of the predicted amino acid sequence. The sequence was 61.6% identical with that of silk moth glycyl-tRNA synthetase. Several very highly conserved regions were identified, including the single class II synthetase motif region and an N-terminal region similar to one found in at least three other synthetases. Near identity in other regions suggested that they also had important functions. Expression of the cDNA in Escherichia coli yielded a protein of expected size that reacted with the autoantibodies and was active as glycyl-tRNA synthetase.

Analysis of the specificity of anti-PM-Scl autoantibodies

OBJECTIVE

To compare the specificity of anti-PM-Scl autoantibodies in serum samples from 43 patients with myositis, scleroderma, or both.

METHODS

Anti-PM-Scl immunoprecipitates from HeLa cell extract were used as antigen for immunoblot analyses to determine the antigenic components. A series of complementary DNA fragments was expressed in Escherichia coli for immunoblot examination of the reaction with the 100-kd protein.

RESULTS

The immunoblot against immunoprecipitates was sensitive and specific for detecting reactions with components of the PM-Scl antigen: 42 of 43 sera (97.7%) reacted with the 100-kd, 27 of 43 (62.8%) with the 70-kd, and 5 of 43 (11.6%) with the 37-kd protein (not previously recognized as antigenic). Forty-one sera reacted with N-terminal protein S1 (amino acids 11-437), 39 with central protein S2 (amino acids 439-749), and 24 with C-terminal protein S3 (amino acids 750-882). Of 42 sera tested, 28 (66.7%) reacted most strongly with S1, and 6 (14.3%) reacted most strongly with S2. Absorption studies implied additional, conformational epitopes not present on the bacterially expressed antigen.

CONCLUSION

There was an overall similarity in reactivity to the PM-Scl antigen, but there were differences in the reactivity to the 70-kd and 37-kd proteins, as well as in the relative strength of the reactivity to the S2 protein.

Bone mass, rates of osteoporotic fractures, and prevention of fractures: are there differences between China and Western countries?

Fractures are one of the most common causes of disability in older women. The quantity and density of bone decreases with age. Most types of fractures increase as bone density declines. But most of the knowledge about causes and prevention of fractures comes from studies performed in Western countries. Asian women appear to have similar or slightly lower bone density that may be a result of their smaller size. They appear to have a lower risk of hip fracture than Whites, which may be a result of their shorter hip axis. The risks of other types of fractures in Chinese women is less well defined and reasons for differences in the rates of osteoporotic fractures between China and Western countries remain to be explored. A study is underway in Beijing to describe the risks and potential causes of fractures among older women in urban China. Randomized trials in Western countries have demonstrated that calcium and vitamin D, estrogen, calcitonin, or bisphosphonates can reduce the rate of fractures. increased intake of calcium and vitamin D may be the most effective approach to preventing fractures in China, but this should be tested in a randomized trial.

[A study on classification of Xanthomonas by isoelectric focusing]

Studying Xanthomonas strains of 4 species and 29 pathovars by isoelectric focusing, it was shown that the protein patterns were very different among the species and pathovars. Through cluster analysis of IEF date, it was found that the protein pattern differences among certain pathovars were no fewer than that among the species. It revealed that some pathovars could become to be species. There were few differences of 6 protein bands among X. campestris pv. cerealis, X. campestris pv. undulosa and X. campestris pv. hordei which cause bacterial black cheff, so the classification of the three pathovars need to be re-considered. It also showed that isoelectric focusing could be used to classify Xanthomonas below species.

Cloning of a complementary DNA coding for the 100-kD antigenic protein of the PM-Scl autoantigen

Anti-PM-Scl antibodies are associated with polymyositis-scleroderma overlap or either disease alone. Among sera from 39 patients with anti-PM-Scl, 23 recognized the 100-kD band in immunoblot against HeLa cell extract, 16 of which also stained the 70-kD band. A human thymocyte lambda gt11 cDNA expression library was screened with anti-PM-Scl serum, and two clones were identified whose products reacted with 33 and 37 of 39 anti-PM-Scl sera, respectively, but none of 26 negative control sera. Affinity-purified antibody reacting specifically with plaques of the clone stained the 100-kD band on immunoblot, reacted with nucleoli of HEp-2 cells, and immunoprecipitated the PM-Scl protein complex. Partial sequences of both inserts were identical. One insert was fully sequenced, and additional 5' and 3' sequence was obtained using a gene-specific primer to form a cDNA with HeLa cell RNA as template followed by PCR. The complete nucleotide sequence included 2,739-bp coding for a predicted full-length protein of 98,088 D. There was no homology with the PM-Scl 75-kD protein and no significant homology with other proteins. A mixed-charge cluster was identified, with 22 charged amino acids of 37. In conclusion, the full-length cDNA sequence was determined coding for the PM-Scl 100-kD protein, the most commonly antigenic protein of the PM-Scl complex.