Posterior interosseous syndrome revisited.

The question of how the supinator syndrome and the posterior interosseous syndrome are (or are not) related has not been well discussed in the literature. The anatomy of the radial nerve and its innervations is quite variable, as are the etiology, presentation, and clinical findings in the lesions of the posterior interosseous nerve. The present study was based on a retrospective review of the electrodiagnostic records of 12 patients with involvement of the deep radial nerve (posterior interosseous nerve) diagnosed at the EMG lab of New York University Medical Center from 1975 to 1983. Two-thirds of these patients had electrophysiologic abnormalities of the supinator muscle, and in the remainder, the supinator was not involved. All superficial radial nerves had normal evoked mode action potential amplitudes and latencies. We propose that the supinator syndrome is a special case of the posterior interosseous syndrome.

Serum albumin as a predictor of course and outcome on a rehabilitation service.

To determine the effect of nutritional status on the medical course and rehabilitation outcome of patients on an adult rehabilitation service, serum albumin (SA) and total lymphocyte count (TLC) were prospectively studied on 36 patients. Readings were taken on admission (T-1), at which time a Barthel Index Mobility Goal (BIMG) was assigned, and again 4 to 8 weeks after admission (T-2). A Barthel Index Mobility Score (BIMS) was assigned at discharge. Rehabilitation program restrictions due to medical complications correlated negatively with both the SA level at T1 (r = -.328, p less than 0.05) and at T2 (r = -.523, p less than 0.01). The SA level at T2 correlated positively with the BIMS:BIMG ratio (r = .416, p less than 0.05) at discharge, suggesting that SA levels may predict patient mobility outcome.

Two glutamine synthetases from Bacillus caldolyticus, an extreme thermophile. Isolation, physicochemical and kinetic properties.

Two distinctly different glutamine synthetase enzymes (EI and EII) have been isolated from the extreme thermophile Bacillus caldolyticus, grown on chemically defined medium at 70 degrees C. Purification to homogeneity mainly involves affinity chromatography and heat treatment with substrate protection. Biosynthesis of total enzyme activity can be repressed by at least 8-fold by high ammonia, with synthesis of EI being repressed more strongly than EII. A variety of chemical and biochemical tests failed to provide evidence for regulation of EI or EII by covalent modification, e.g. proteolysis, phosphorylation, or adenylylation. Neither of the thermophiic enzymes will cross-react with antibodies for the Escherichia coli or Bacillus subtilis glutamine synthetases. Both enzymes are composed of 12 subunits, each approximately 51,000 daltons. However, EI and EII differ significantly in their amino acid composition, isoelectric points (5.2 and 5.5, respectively), rates of migration on polyacrylamide electrophoresis gels at pH 6.8, and kinetic properties, EI is more active with Mg(II) than with Mn(II), but EII is more active with Mn(II) than Mg(II). Cd(II) activates EII more than EI, and only EI shows activity with Co(II). For both enzymes, the Mn(II)-stimulated activity is optimal at pH 6.0 to 6.5, with Mn(II)/ATP = 1.0, but the pH optimum with Mg(II) is near pH 7.5, however, with a ratio of Mg(II)/ATP > 2. Substrate Km values at 70 degrees C differ for EI versus EII but are quite comparable to those seen for mesophilic glutamine synthetases. Studies with structural analogs of substrates indicate that active site specificity is maintained at extreme temperatures: substitution of alpha-OH for alpha-HN2 is allowed, but unfavorable changes occur upon substitution of methyl groups for the alpha-H or onto the alpha-NH2 of L-Glu, and for D-Glu or L-Asp. EII is almost absdolutely specific for ATP, but EI can also use ITP, GTP, and UTP as substrates to some extent. The divalent metal ion that is present can affect both specificity for analogs and substrate Km values. Kinetic binding plots (v versus [S]) are biphasic for NH3 and L-Glu with the more active forms of each enzyme, EI-Mg and EII-Mn, respectively; but no positive cooperativity is observed. ATP binding is strictly hyperbolic, in contrast to the positive cooperativity previously observed with other Bacillus sp. enzymes. For purified EI and EII, Arrhenius plots are nonlinear with Mn(II) or Mg(II), exhibiting slope changes in the range of 55-65 degrees C; however, for EI-EII mixtures in crude cell extracts these plots are nearly linear.

Glutamine synthetase of Bacillus stearothermophilus. Regulation, site interactions, and functional information.

The action of various feedback modifiers on Bacillus stearothermophilus glutamine synthetase has been investigated by initial velocity kinetics, using the Mn2+-stimulated biosynthetic assay at 55 degrees C. The most potent inhibitors, used singly, are AMP, L-glutamine, and L-alanine. Other modifiers of significance include glycine, CTP, L-histidine, glucosamine 6-phosphate, and GDP. Marked synergism of action is observed for AMP in the presence of L-glutamine, L-histidine, ADP, or glucosamine 6-phosphate (glucosamine-6-P), and for CTP with ADP or GDP. Inhibition by saturating levels of many modifiers is either less than 100%, or is not overcome by elevated substrate levels, or both. This argues for modifier binding sites separate from substrate sites, notably in the cases of AMP, L-glutamine, glycine, L-alanine, glucosamine-6-P, and CTP. Glycine and L-alanine are Vmax inhibitors, whereas L-glutamine, glucosamine-6-P, GDP, and CTP alter the binding of L-glutamate. ADP and L-histidine apparently can compete directly with MnATP, but AMP alters Mn-ATP binding from a separate site. The action of several modifiers requires or is enhanced by bound substrates. Considerable antagonistic interaction is observed in experiments with modifier pairs, but the most potent inhibitors show synergistic or cumulative (independent) interactions. One may interpret antagonistic effects as due to (a) overlapping modifier domains, or (b) separate but antagonistically interacting sites. Either interpretation leads to a scheme for modifier-substrate and modifier-modifier site interactions in which the thermophilic enzyme must maintain and stabilize a great deal of complex functional information under extreme environmental conditions.

Maintainance of specificity, information, and thermostability in thermophilic Bacillus sp. glutamine synthetase.

Glutamine synthetase has been purified to homogeneity from B. subtilis (37 degrees) B. stearothermophilus (55 degrees), and B. caldolyticus (75 degrees). Those characteristics compared include size (6.0 +/- 0.3 X 10(5) daltons), quaternary structure (12 SU) amino acid content, substrate Km's and specificity for structural analogs, metal ion activation, number and kind of separate feedback modifier sites, and the complexity of modifier-substrate and modifier-modifier site interactions. Although the 37 degrees and 55 degrees systems are quite similar, the 75 degrees system shows important alterations in substrate specificity and modes of modifier action. Whereas at 37 degrees and 55 degrees AMP inhibits synergistically with amino acids (glycine, glutamine, histidine), the 75 degrees enzyme is inhibited directly by the products ADP, (which assumes the role of AMP) and glutamine, plus other ligands. Ligand binding domains are compared and found to be very different. Thermostabilization occurs by (a) protection by bound L-glutamate, (b) protein aggregation, (c) trends in the content of total polar residues, total Asx + Flx residues, the average hydrophobicity, and (d) disulfide bond cross-linking. Such studies provide insights to molecular evolution occurring with changes in environmental stress.