Functional analysis of PTPN11/SHP-2 mutants identified in Noonan syndrome and childhood leukemia

Noonan syndrome (NS) is characterized by short stature, characteristic facial features, and heart defects. Recently, missense mutations of PTPN11, the gene encoding protein tyrosine phosphatase (PTP) SHP-2, were identified in patients with NS. Further, somatic mutations in PTPN11 were detected in childhood leukemia. Recent studies showed that the phosphatase activities of five mutations identified in NS and juvenile myelomonocytic leukemia (JMML) were increased. However, the functional properties of the other mutations remain unidentified. In this study, in order to clarify the differences between the mutations identified in NS and leukemia, we examined the phosphatase activity of 14 mutants of SHP-2. We identified nine mutations, including a novel F71I mutation, in 16 of 41 NS patients and two mutations, including a novel G503V mutation, in three of 29 patients with leukemia. Immune complex phosphatase assays of individual mutants transfected in COS7 cells showed that ten mutants identified in NS and four mutants in leukemia showed 1.4-fold to 12.7-fold increased activation compared with wild-type SHP-2. These results suggest that the pathogenesis of NS and leukemia is associated with enhanced phosphatase activity of mutant SHP-2. A comparison of the phosphatase activity in each mutant and a review of previously reported cases showed that high phosphatase activity observed in mutations at codons 61, 71, 72, and 76 was significantly associated with leukemogenesis.     

Airway occlusion pressure (P0.1) — A useful predictor for the weaning outcome in patients with acute respiratory failure —

Twenty-five patients who required mechanical ventilatory support (MVS) after major surgery or severe burns were studied to determine whether airway occlusion pressure (P_0.1) is a clinically useful indicator to predict the success or failure of the weaning trial. A total of 33 weaning trials were attempted on these patients. Of the 33 trials, 24 were followed by successful weaning and 9 by failure. Although the success group, when compared with the failure group, had a lower respiratory rate (P 0.001), a lower minute ventilation (P 0.001), a higher maximal voluntary ventilation to minute ventilation ratio (P 0.01) and a higher forced vital capacity (P 0.05), no threshold values separated the success from the failure group. The alveolar-arterial P_{O 2} gradient, with an Fi _{O 2} of 1.0, in weaning success and failure showed no statistical difference. In contrast, all patients in the success group had a P_0.1 of less than 3.5cmH₂O and those in the failure group had a P_0.1 of greater than 3.5cmH₂O (P 0.001). We conclude that P_0.1 is a clinically superior indicator for discontinuing MVS in patients with acute respiratory failure.(Okamoto K, Sato T, Morioka T: Airway occlusion pressure (P_0.1)—A useful predictor for the weaning outcome in patients with acute respiratory failure—. J Anesth 4: 95–101, 1990)     

Accumulation of L-[2-(F-18)]fluorophenylalanine in peri-infarct area in a patient with acute cerebral infarction

We studied the brain uptake of amino acid in a patient with acute cerebral infarction with L-[2-(F-18)] fluorophenylalanine and positron emission tomography. The increased accumulation of the ligand was specifically found in the peri-infarct area where oxygen metabolism was still maintained but decreased later in the 72-day follow-up period. The kinetic analysis revealed that increased accumulation was not due to increased transport from the blood to the brain but to delayed washout from the brain to the blood. Although the mechanism is still unknown, abnormally high accumulation of L-[F-18]fluorophenylalanine may predict delayed neuronal changes after ischemic insults of the brain.     

Monozygotic twins with suspected hereditary sensory and autonomic neuropathy (HSAN) type V

We report a pair of 1-year-5-month-old female monozygotic twins with generalized loss of pain sensation, but without impairment of other sensory modalities and the diaphoretic function. Routine electrophysiological investigations revealed no abnormalities. Morphometric analysis of biopsied sural nerve showed that the number of small myelinated fibers was reduced and that of unmyelinated fibers was normal or mildly reduced. On the basis of these findings, we suspected a diagnosis of a rare disorder, HSAN type V, which has not previously been reported in Japan.     

Development of the local medical service network system. Integration of medical service with the network system between university hospital and other medical institutions.

Although every medical institution always make efforts to provide best services for the patients, it tends to be insufficient to send the patient's information and share them with other medical institutions. It is partly because in the Japanese medical care system there is no obligation to inform patients' medical information to other medical institutions. To provide effective and cost-effective medical service, we made a local network system between university hospital and other medical institutions. The system contributes to clarify the role of medical institutions and the continuity of medical service. For the next step, we must construct the home-care information service network towards the total service for the patients.     

Changes in refraction caused by induction of acute hyperglycemia in healthy volunteers

PURPOSE: To determine whether the myopic changes and ocular hypotension after a glucose load are caused by hyperglycemia. METHODS: Oral glucose tolerance tests were conducted on seven healthy young subjects with normal vision. The changes in the hematologic parameters and the refractive system were measured periodically for 150 minutes after the glucose load. RESULTS: After the glucose load, there was an increase in plasma glucose level and the level of plasma osmosis, ocular hypotension, a myopic change in refractive power, shallowing of the anterior chamber, and a thickening of the lens. The degree of the myopic change exceeded the power of the residual accommodation. Normalization of the plasma glucose level led to a normalization of the intraocular pressure and a reversal of the myopic changes. CONCLUSIONS: These findings suggest that the myopic changes that accompanied hyperglycemia were caused by a thickening of the lens resulting from a decrease in the tension of the zonule fibers of Zinn, and were secondary to ocular hypotension. Hyperopia appeared to be caused by the reversal of the myopia after normalization of plasma glucose levels.     

Effects of lactate on intracellular pH and hypercontracture during simulated ischemia and reperfusion in cardiac ventricular myocytes of the guinea pig.

Effects of lactate on changes in intracellular pH (pHi) and contractility during simulated ischemia and reperfusion were examined in single myocytes of the guinea pig cardiac ventricle. The conditions of simulated ischemia were produced by the exchange of perfusion medium from the standard one oxygenated with 95% O2-5% CO2 gas (pH 7.4) to one containing no glucose, 8 mM K+, and 0-30 mM sodium-D,L-lactate and was gassed with 90% argon - 10% CO2 (pH 6.6). The pHi was decreased by the simulated ischemia from approx. 7.3 to approx. 6.9 regardless of lactate concentration, while the rate of pHi decrease was increased by lactate in a concentration-dependent manner. The contraction induced by electrical stimulation disappeared faster in the presence of lactate. The incidence of irreversible hypercontracture of myocytes was significantly reduced by 20-30 mM lactate. The overshoot of pHi to approx. 7.7 and excess contractions were induced by withdrawal of lactate during the reperfusion, but not observed when lactate was continuously present. The recovery of normal contractility during reperfusion was facilitated by lactate. It can be concluded that lactate added to or removed from the perfusion medium increases the rate of pHi change under the simulated ischemia and reperfusion, respectively, and that the continuous presence of lactate reduces cell injury under these conditions.     

Repair of a ruptured aortic arch aneurysm complicated by postoperative paraplegia: Report of a case

We report herein the rare case of a 79-year-old man who suffered permanent paraplegia after undergoing an otherwise successful total arch replacement for a ruptured aortic arch aneurysm. During cardiopulmonary bypass, perfusion to the distal aorta was maintained from the femoral artery, and postoperative aortography showed intact tributaries from the aorta including the intercostal arteries. Postoperative paraplegia is an extremely rare complication of operations on the aortic arch; however, we speculate that the paraplegia in this patient could be attributed either to a steal phenomenon involving the radicular artery, or to the anatomical particularity of the spinal cord artery described by Cole and Gutelius as the segmental system.