Alanine, not ammonia, is excreted from N2-fixing soybean nodule bacteroids

Symbiotic nitrogen fixation, the process whereby nitrogen-fixing bacteria enter into associations with plants, provides the major source of nitrogen for the biosphere. Nitrogenase, a bacterial enzyme, catalyzes the reduction of atmospheric dinitrogen to ammonium. In rhizobia-leguminous plant symbioses, the current model of nitrogen transfer from the symbiotic form of the bacteria, called a bacteroid, to the plant is that nitrogenase-generated ammonia diffuses across the bacteroid membrane and is assimilated into amino acids outside of the bacteroid. We purified soybean nodule bacteroids by a procedure that removed contaminating plant proteins and found that alanine was the major nitrogen-containing compound excreted. Bacteroids incubated in the presence of ¹⁵N₂ excreted alanine highly enriched in ¹⁵N. The ammonium in these assays neither accumulated significantly nor was enriched in ¹⁵N. The results demonstrate that a transport mechanism rather than diffusion functions at this critical step of nitrogen transfer from the bacteroids to the plant host. Alanine may serve only as a transport species, but this would permit physiological separation of the transport of fixed nitrogen from other nitrogen metabolic functions commonly mediated through glutamate.     

Interpretation of the Disk Diffusion Susceptibility Test for Amikacin: Report of a Collaborative Study

Because excessively high rates of false resistance have been encountered with the 10-mug amikacin disk in diffusion susceptibility tests, a study was performed to examine existing zone diameter interpretative criteria and to compare the accuracy of 10- and 30-mug amikacin disks by the error rate-bounded classification scheme. Although current zone diameter interpretative criteria eliminate false susceptibles, there is an unacceptably high rate of false resistants. This problem can be resolved in most instances by revising the zone diameter interpretative criteria for the 10-mug disk (resistant, /=12 mm) or, preferably, by replacing the 10-mug disk with a 30-mug disk and adopting new interpretative criteria (resistant, /=17 mm). Because of significant differences in performance among media, it is necessary to include Pseudomonas aeruginosa ATCC 27853 among controls routinely tested and to exclude from use lots of Mueller-Hinton agar yielding results outside the 75% tolerance (90% confidence) limits for amikacin.     

Prognostic value of Cathepsin D expression in breast cancer: Immunohistochemical assessment and correlation with radiometric assay

BACKGROUND:: The prognostic significance of Cathepsin D and optimal methodologiesto measure Cathepsin D in breast cancers are controversial. PATIENTS AND METHODS:: Quantitative (immunoradiometric) and semiquantitative (immunohistochemical)assays for Cathepsin D expression were compared using 25 breastcarcinomas. Immunohistochemical Cathepsin D results were derivedusing 3 different anti-Cathepsin D antibodies and significantassociations between immunohistochemical and radiometric CathepsinD data were observed for each reagent. Immunohistochemical analysisof Cathepsin D expression was performed on nearly 500 fixed-embeddedarchival breast cancers with long-term patient follow-up using2 anti-Cathepsin D antibodies (CDR2-11/23, IC11). RESULTS:: The immunohistochemical reagents recognized generally overlappingsubsets of Cathepsin D positive tumors (correlation co-efficient0.54; p – 0.00016). Correlations between Cathepsin D dataand clinical, histologic or biologic features differed for eachantibody. For the node-negative patient subset, Cathepsin Dimmunopositivity correlated with erbB-2 and stress-responseprotein 27 overexpression but not survival. Cathepsin D positivitywas associated with subsequent distant metastasis and estrogenreceptor positivity in node positive patients. Univariate analysisof all patients suggested that Cathepsin D immunopositivitymay be predictive of a reduced metastasis-free but not overallsurvival. Multivariate analysis, however, failed to confirman independent prognostic value for Cathepsin D in breast cancerpatients. CONCLUSIONS:: These data do not confirm an independent prognostic significancefor Cathepsin D using immunohistochemical methods on breastcancers. breast cancer, Cathepsin D, immunoassay, immunohistochemistry, prognostic marker     

Pelvic lymphadenectomy for staging clinically localized prostate cancer Indications, Complications, and Results in 217 Cases

We reviewed the findings of 217 consecutive pelvic lymphadenectomies performed in patients with clinically localized prostatic carcinoma focusing particular attention on the importance of completely removing the hypogastric lymph nodes and on the operative complications associated with a more extensive dissection. Metastatic disease was identified in the lymph nodes of 127 patients (58.6%). The hypogastric nodes were involved in two thirds of the patients with lymph node metastases, and in 29 percent the hypogastric nodes were the only site of metastasis. No increased operative morbidity was documented as a result of extending the level of the pelvic lymphadenectomy to include the lower hypogastric nodes. We conclude that although the lower hypogastric lymph nodes have not been routinely included in most pelvic lymphadenectomies, their removal is important in detecting metastases.     

Thrombin receptor on rat primary hippocampal neurons: coupled calcium and cAMP responses

We have tested the hypothesis that hippocampal neurons respond to thrombin via a neuronal thrombin receptor. A human neuroblastoma cell line, SK-N-SH, known to be thrombin responsive morphologically, responded both to thrombin and thrombin receptor agonist peptide (TRAP 42–55) with elevation of intracellular calcium. In Western blots of membranes from SK-N-SH cells and cultured rat hippocampal neurons using an antibody against the N-terminal peptide of the human thrombin receptor, putative receptor proteins of 66 and 47 kDa were detected in both cells. Neurons were treated with thrombin and TRAP 42–55 (TRAP-14) to determine their effects on intracellular levels of calcium and cAMP. Only 10% of the neurons showed a rapid response to thrombin, but most responded rapidly to agonist peptide with a prolonged elevation of intracellular free calcium. Neuronal cAMP levels were decreased by 40% after 24 h thrombin treatment. This decrease in cAMP level could be blocked by both the G_i-protein inhibitor, pertussis toxin, and the thrombin inhibitor, hirudin, suggesting a possible involvement of G_i-protein-coupled receptor activation. Furthermore, rapid calcium and cAMP responses were apparently induced by pre-treatment of neurons with thrombin for 24 h and subsequent washout. In summary, these data indicate that rat primary hippocampal neurons have thrombin receptors whose responses to thrombin apparently are up-regulated by 24 h thrombin pre-treatment. These results may have implications for synaptic remodeling, learning and memory.     

Complications experienced in the rehabilitation of zone I flexor tendon injuries with dynamic traction splinting

A retrospective review of all flexor tendon repairs done between January 1985 to June 1987 determined the complication rate with our method of rehabilitation. One hundred sixty-three flexor tendon lacerations in 83 patients were reviewed. Follow-up ranged from 6 to 42 months. All patients participated in the same 12-week rehabilitation protocol. All patients had passive motion exercises of the interphalangeal joints in the first 2 weeks. We believe that passive stretching of zone I injuries during the first 2 weeks contributed to the zone I complication rate. Of the 20 patients with zone I tendon-to-tendon repairs, 7 patients had significant complications. The 35% complication rate found with zone I injuries has prompted us to modify our postoperative rehabilitation protocol in zone I injuries.     

Adaptive critic designs: A case study for neurocontrol

For the first time, different adaptive critic designs (ACDs), a conventional proportional integral derivative (PID) regulator and backpropagation of utility are compared for the same control problem—automatic aircraft landing. The original problem proved to contain little challenge since various conventional and neural network techniques had solved it very well. After the problem had been made much more difficult by a change of parameters, increasingly better performance was observed by going from the simplest ACD to more sophisticated designs, dual heuristic programming having been ranked best of all. This case study is of use in general intelligent control problems for it provides an example of the capabilities of different adaptive critic designs.     

The management of traumatic aortic tear in the multiply-injured patient

Patients with traumatic aortic tears and severe life-threatening associated injuries require early and expeditious evaluation and treatment in order to improve survival. Diagnostic and treatment priorities, however, are not clearly established in this subset of patients. The purpose of this retrospective analysis was to help identify successful diagnostic and treatment priorities in this group of patients. Between 1979–1989 the medical records of all patients sustaining blunt chest trauma resulting in a traumatic aortic tear were reviewed. There were 11 patients with multiple injuries and this diagnosis was treated at Boston University Medical Center. Five patients had diagnostic peritoneal lavage or an exploratory laparotomy prior to a thoracotomy. Four patients had only a thoracotomy. Two patients in this series had a thoracotomy prior to treatment of suspected intraabdominal injuries. One of these two patients died. Our overall survival rate was 82%. This series suggests that the management sequence in patients with coexistent injuries should include treatment of severe associated injuries prior to treatment of the aortic injury and that initial treatment of traumatic aortic tears is appropriate if there is no evidence of severe life-threatening trauma.