Regulation of glutamine synthetase, aspartokinase, and total protein turnover in Klebsiella aerogenes.

When suspensions of Klebsiella aerogenes are incubated in a nitrogen-free medium there is a gradual decrease in the levels of acid-precipitable protein and of aspartokinase III (lysine-sensitive) and aspartokinase I (threonine-sensitive) activities. In contrast, the level of glutamine synthetase increases slightly and then remains constant. Under these conditions, the glutamine synthetase and other proteins continue to be synthesized as judged by the incorporation of [14C]leucine into the acid-precipitable protein fraction and into protein precipitated by anti-glutamine synthetase antibodies, by the fact that growth-inhibiting concentrations of chloramphenicol also inhibit the incorporation of [14C]leucine into protein and into protein precipitated by anti-glutamine synthetase antibody, and by the fact that chloramphenicol leads to acceleration in the loss of aspartokinases I and III and promotes a net decrease in the level of glutamine synthetase and its cross-reactive protein. The loss of aspartokinases I and III in cell suspensions is stimulated by glucose and is inhibited by 2,4-dinitrophenol. Glucose also stimulates the loss of aspartokinases and glutamine synthetase in the presence of chloramphenicol. Cell-free extracts of K. aerogenes catalyze rapid inactivation of endogenous glutamine synthetase as well as exogenously added pure glutamine synthetase. This loss of glutamine synthetase is not associated with a loss of protein that cross-reacts with anti-glutamine synthetase antibodies. The inactivation of glutamine synthetase in extracts is not due to adenylylation. It is partially prevented by sulfhydryl reagents, Mn2+, antimycin A, 2,4-dinitrophenol, EDTA, anaerobiosis and by dialysis. Following 18 h dialysis, the capacity of extracts to catalyze inactivation of glutamine synthetase is lost but can be restored by the addition of Fe2+ (or Ni2+) together with ATP (or other nucleoside di- and triphosphates. After 40-60 h dialysis Fe3+ together with NADH (but not ATP) are required for glutamine synthetase inactivation. The results suggest that accelerated protein degradation in cells exposed to nitrogen-limited conditions reflects the differential destruction of some proteins, including aspartokinases I and III, in order to sustain the biosynthesis of others such as glutamine synthetase. The loss of glutamine synthetase activity in cell-free extracts is likely mediated in part by mixed-function oxidation systems and could represent a 'marking' step in protein turnover.

COTA (colon-ovarian tumor antigen). An immunohistochemical study.

A goat anti-serum was prepared against mucinous ovarian cyst fluid and absorbed with normal colon and a variety of normal tissues until the only residual immunoreactivity was directed against colon cancer and ovarian tumor mucin. The set of antigenic determinants defined by this anti-serum has been called COTA, standing for colon-ovarian-tumor-antigen. This highly absorbed anti-serum (anti-COTA) was used for immunohistochemical staining of 42 different tissues in parallel with staining with a goat anti-CEA, which was also highly absorbed. The results suggest that COTA is a highly sensitive and specific antigen for colon carcinoma and may have potential for the early detection of malignant changes predictive of cancer of the colon.

Aspiration cytology of metastatic chordoma. A case report.

A patient with previously diagnosed sacrococcygeal chordoma presented with multiple skin nodules. Cytologic examination of an aspirate from one of these nodules showed syncytial clusters of hyperchromatic cells surrounded by extracellular mucin. The characteristic physaliphorous cells, although present in a biopsy of the primary sacrococcygeal tumor, were not observed in the aspirate or on histopathologic examination of three excised skin metastases. That chordoma metastases may lack physaliphorous cells should be recognized.

Carcinoma of the ureter with extensive squamous differentiation and positive immunoperoxidase staining for carcinoembryonic antigen: a case report.

A case of ureteral carcinoma with extensive squamous differentiation and positive staining for carcinoembryonic antigen by the immunoperoxidase method is presented. Ureteral carcinoma should be added to the list of tumors that may produce carcinoembryonic antigen or antigen-like material.

Osler's nodes, pseudoaneurysm formation, and sepsis complicating percutaneous radial artery cannulation.

Percutaneous arterial cannulation is useful for hemodynamic monitoring and frequent arterial blood gas determinations in selected intensive care patients. However, this procedure is not without risk. We report a case of localized Osler node formation, distal to a radial artery catheter, associated with sepsis, pseudoaneurysm formation, and thrombosis at the site of catheterization. Complications of this technique require aggressive medical and, in selected cases, surgical intervention.

Effects of insulin, glucose, and amino acids on protein turnover in rat diaphragm.

A simple method is described for measuring rates of protein synthesis and degradation in isolated rat diaphragm. Muscles incubated in Krebs-Ringer bicarbonate buffer showed a linear rate of synthesis for 3 hours. At the same time, the muscle released tyrosine and ninhydrin-positive material, primarily amino acids, at a linear rate. This release was not a nonspecific leakage of material from the intracellular pools, but reflected net protein degradation. Tyrosine was chosen for studies of protein turnover, since it rapidly equilibrates between intracellular pools and the medium, it can be measured fluorometrically, and it is neither synthesized nor degraded by this tissue. To follow protein degradation independently of synthesis, muscles were incubated in the presence of cycloheximide. Under these conditions, the amount of tyrosine in the intracellular pools was constant, while the muscle released tyrosine at a linear rate. This tyrosine release was used as a measure of degradation. This preparation was used to study the influence of various factors known to be important for muscle growth on protein synthesis and degradation. Similar effects were obtained with diaphragms of normal and fasted rats although the latter showed decreased synthesis and increased protein degradation. Insulin by itself not only stimulated synthesis but also inhibited protein degradation (even in the presence of cycloheximide). These two effects served to reduce the net release of tyrosine from muscle protein to comparable extents. Effects of insulin on synthesis and degradation were greater when glucose was also present in the medium. Glucose by itself inhibited protein degradation but in the absence of insulin glucose had no significant effect on synthesis. Nevertheless, glucose stimulated incorporation of radioactivive tyrosine into protein, but this effect was due to an increased intracellular specific activity. Unlike glucose neither beta-hydroxybutyrate or octanoic acid had any demonstrable effects on protein degradion. The addition of amino acids at plasma concentrations both promoted protein synthesis and inhibited degradation in the diaphragm. Five times normal plasma concentrations of the amino acids had larger effects. The three branched chain amino acids together stimulated synthesis and reduced degradation, while the remaining plasma amino acids did not affect either process significantly. Thus leucine, isoleucine, and valine appear responsible for the effects of plasma amino or isoleucine and valine together, also were able to inhibit protein degradation and promote synthesis.

Turnover of bacterial glutamine synthetase: oxidative inactivation precedes proteolysis.

We partially purified a preparation from Escherichia coli that proteolytically degrades the enzyme glutamine synthetase [L-glutamate:ammonia ligase (ADP-forming), EC 6.3.1.2]. The degradation is at least a two-step process. First, the glutamine synthetase undergoes an oxidative modification. This modification leads to loss of catalytic activity and also renders the protein susceptible to proteolytic attack in the second step. The oxidative step displays characteristics of a mixed-function oxidation, requiring both molecular oxygen and a reduced nucleotide. This step can also be catalyzed by a purified, mammalian cytochrome P-450 system, as well as by a model system consisting of ascorbic acid and oxygen. Catalase blocks this oxidative modification step. Thus, the overall process of proteolytic degradation can be observed only if care is taken to remove catalase activity from the extracts. The inactivation reaction is dependent on the state of adenylylation of the glutamine synthetase, suggesting that this a physiologically important reaction. If so, then mixed-function oxidases are now implicated in the process of intracellular protein turnover.