Measurement of the Expiratory Ammonia Concentration and its Clinical Significance

Alghough gaseous ammonia (NH₃) can freely enter cells through the plasma membrane where NH₃ is cyto(neuro)toxic, NH₃ and ionic ammonia (NH₄ ⁺) contents have not been studied in biological materials. We developed a new method for measurement of expiratory NH₃ concentration, which may reflect blood NH₃ concentrations. The method is a sensor tube type-gas assay system. Expiratory NH₃ concentrations in patients with chronic liver diseases increased when their blood ammonia (NH₄ ⁺+NH₃) concentrations increased above 90 μg/dl (normal range; 12–66 μg/dl). However, cirrhotic patients, who had relatively higher expiratory NH₃ concentration compared to blood NH₃ concentrations (calculated from Henderson-Hasselbalch formula), were found to have subclinical encephalopathy. Measurement of experatory NH₃ concentration may be of clinical significance for the diagnosis of encephalopathy associated with hyperammonemia.     

Myocardial energetics and cardiac function of preserved rat heart.

We studied mitochondrial function in relation to ATP production and its relationship with myocardial oxygen consumption (VO2) and total mechanical energy using isolated rat hearts after 8, 12, and 24 h of hypothermic preservation. In isovolumic contraction, ventricular contractility and total mechanical energy were respectively assessed by the end-systolic elastance (Ees) and pressure-volume area (PVA). Ees significantly decreased after hypothermic ischemia, although the difference was not significant between 8 and 12 h. In contrast, VO2 measured at each left ventricular volume increased after hypothermic ischemia. PVA and VO2 were found to stay in linear correlation after prolonged hypothermic ischemia, although VO2 at null PVA and VO2 to PVA ratios significantly increased after hypothermic ischemia, especially after 12-h ischemia. Mitochondrial oxidative phosphorylation significantly decreased after hypothermic ischemia for longer than 12 h. These results indicate that mitochondrial oxidative phosphorylation was impaired due to long time hypothermic ischemia especially after 12-h ischemia. We conclude that energy uncoupling between VO2 and PVA in hypothermically preserved heart is attributable to disturbed mitochondrial oxidative phosphorylation and that 8 h is a critical point for efficient conversion of energy from VO2 into PVA in rat heart.     

Endoscopic approach to pulmonary diseases: Usefulness of the mediastinoscopy

The purposes of this study are to show the diagnostic values and the role of the mediastinoscopy for the respiratory diseases. From 1971 to 1998, mediastinoscopy were performed on 1664 patients admitted to our hospital with respiratory diseases. For the superior mediastinal diseases, mediastinal tumor and lymphadenopathies without cancer, two or three samples were obtained by mediastinoscopy. For lung cancer, biopsy was routinely performed at the 6 nodal stations, right and left paratracheal (#2), right and left tracheobronchial (#4), pretracheal (#3), and subcarinal (#7) lymphnodes. From 1994, we have used video-mediastinoscopy, which was combined with scope and TV-camera. Using video-mediastinoscopy, many staffs could observe the mediastinal findings on TV-monitor during mediastinal manipulation. The positive findings were observed in 17% (221/1299) for lung cancer, 100% (32/32) for sarcoidosis, 100% (2/2) for malignant lymphoma, 65% (11/17) for mediastinal tumor, 9.8% (13/132) for pulmonary tuberculosis. The positive rate according to the histological types of lung cancer were 20.5% (148/721) for adenocarcinoma, 9.4% (39/415) for squamous cell carcinoma, 31.6% (24/76) for small cell carcinoma, 21.3% (10/47) for large cell carcinoma. Complications developed in a total of 3.6%, and these were bronchial arterial damage(1.8%), recurrent nerve paralysis(0.7%), azygos vein damage (0.4%), pleural rupture(0.4%), superior vena cava damage(0.2%) and tracheal laceration(0.1%). However, there were no severe complications and operative deaths in this series. Mediastinoscopy is a minimal invasive and safety surgical procedure that is widely used as a diagnostic method for investigating the superior mediastinum, mediastinal tumor and lymphadenopathies. It is useful for obtaining histological diagnosis, as well as for staging lung cancer. Video-mediastinoscopy is more safety and educational, because many staffs could observe the findings.     

Case Report: Determination of Primary Foci of Metastatic Tumors by p53 Mutational Analysis in Intraesophageal Multiple Carcinomas

It is well known that squamous carcinomasfrequently develop multifocally, either synchronously ormetachronously, in the upper aerodigestive tract (1).Such phenomena were first reported by Slaughter et al in 1953, and they were named fieldcancerization (2). Using recent molecular biologytechniques, these multiple carcinomas have been revealedto arise from independent origins (3). Esophagealcarcinomas have been reported to frequently metastasize tothe lymph nodes even at the early stage of tumorextension (4). Furthermore, simultaneous multifocalcancer development is not rare in the esophagus (5). In cases of intraesophageal multiple carcinomaswith lymph node metastases, the primary focus of themetastatic tumors cannot be identified by conventionalhistologic examination. Here we report a case of intraesophageal multiple carcinomas in whichthe attributed foci of lymph nodal metastases could beclearly identified by analyzing the p53 gene mutationalstatus used as a clonal marker.     

Anti‐high mobility group box 1 monoclonal antibody ameliorates experimental autoimmune encephalomyelitis

High mobility group box 1 (HMGB1) is an established inflammatory mediator when released from cells. Recent studies have implicated extracellular HMGB1 in the pathogenesis of various autoimmune diseases. The objective of this study was to determine whether HMGB1 could be a therapeutic target for experimental autoimmune encephalomyelitis (EAE). In this study, an anti‐HMGB1 monoclonal antibody was injected intraperitoneally into a mouse model of EAE. We also measured serum cytokines levels in EAE and anti‐HMGB1 monoclonal antibody‐treated EAE. As a result, intraperitoneal injection of an anti‐HMGB1 monoclonal antibody ameliorated the clinical and pathological severity of EAE and attenuated interleukin‐17 up‐regulation in serum. In conclusion, HMGB1 is involved in EAE pathogenesis and could trigger inflammation in the central nervous system. The novel aspect of this study is the demonstration that anti‐HMGB1 ameliorates EAE. HMGB1 may be a novel therapeutic strategy for multiple sclerosis.     

The structure of POMGNT2 provides new insights into the mechanism to determine the functional O-mannosylation site on α-dystroglycan

Defects in the O-mannosyl glycan of α-dystroglycan (α-DG) are associated with α-dystroglycanopathy, a group of congenital muscular dystrophies. While α-DG has many O-mannosylation sites, only the specific positions can be modified with the functional O-mannosyl glycan, namely, core M3-type glycan. POMGNT2 is a glycosyltransferase which adds β1,4-linked GlcNAc to the O-mannose (Man) residue to acquire core M3-type glycan. Although it is assumed that POMGNT2 extends the specific O-Man residues around particular amino acid sequences, the details are not well understood. Here, we determined a series of crystal structures of POMGNT2 with and without the acceptor O-mannosyl peptides and identified the critical interactions between POMGNT2 and the acceptor peptide. POMGNT2 has an N-terminal catalytic domain and a C-terminal fibronectin type III (FnIII) domain and forms a dimer. The acceptor peptide is sandwiched between the two protomers. The catalytic domain of one protomer recognizes the O-mannosylation site (TPT motif), and the FnIII domain of the other protomer recognizes the C-terminal region of the peptide. Structure-based mutational studies confirmed that amino acid residues of the catalytic domain interacting with mannose or the TPT motif are essential for POMGNT2 enzymatic activity. In addition, the FnIII domain is also essential for the activity and it interacts with the peptide mainly by hydrophobic interaction. Our study provides the first atomic-resolution insights into specific acceptor recognition by the FnIII domain of POMGNT2. The catalytic mechanism of POMGNT2 is proposed based on the structure.     

Quantitative evaluation of the diagnostic thinking process in medical students

OBJECTIVE: To explore the diagnostic thinking process of medical students. SUBJECTS AND METHODS: Two hundred twenty-four medical students were presented with 3 clinical scenarios corresponding to high, low, and intermediate pre-test probability of coronary artery disease. Estimates of test characteristics of the exercise stress test, and pre-test and post-test probability for each scenario were elicited from the students (intuitive estimates) and from the literature (reference estimates). Post-test probabilities were calculated using Bayes' theorem based upon the intuitive estimates (Bayesian estimates of post-test probability) and upon the reference estimates (reference estimates of post-test probability). The differences between the reference estimates and the intuitive estimates, and between Bayesian estimates and the intuitive estimates were used for assessing knowledge of test characteristics, and ability of estimating pre-test and post-test probability of disease. RESULTS: Medical students could not rule out disease in low or intermediate pre-test probability settings, mainly because of poor pre-test estimates of disease probability. They were also easily confused by test results that differed from their anticipated results, probably because of their inaptitude in applying Bayes' theorem to real clinical situations. These diagnostic thinking patterns account for medical students or novice physicians repeating unnecessary examinations. CONCLUSIONS: Medical students' diagnostic ability may be enhanced by the following educational strategies: 1) emphasizing the importance of ruling out disease in clinical practice, 2) training in the estimation of pre-test disease probability based upon history and physical examination, and 3) incorporation of the Bayesian probabilistic thinking and its application to real clinical situations.