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Biomedical subjects

N Nagayama

Publications and source records attributed to N Nagayama.

14 recordsLinked to original sources
PubMed1995

Finite element analysis of pathogenesis of osteoarthritis in the first carpometacarpal joint.

Stress distribution in the first carpometacarpal joint was analyzed in 49 cadaveric hands using the finite element method to clarify the pathogenesis of osteoarthritis in the joint. The results of the finite element method analysis were compared with those of the contact pressure distribution in the first carpometacarpal joint of cadaveric specimens using pressure-sensitive film, and with the simple roentgenographical and microradiographical manifestations of spur formation, and with histological findings of osteoarthritis to verify the accuracy of the models of computer simulation models. The comparison of these results showed that osteoarthritic changes of the first carpometacarpal joint were found in areas where stress was concentrated during movement of the joint. The saddle shape of this joint is essentially well-designed for the dispersion of normal stress, however minimal displacement due to instability could easily induce osteoarthritis. Furthermore the shallow trapezial configuration may contribute to the high incidence of osteoarthritis changes. The finite element method helped clarify the relationship between stress patterns and osteoarthritis response.

Computer Simulation↗
PubMed1995

[Small airway changes in acute interstitial pneumonia and acute exacerbation of chronic interstitial pneumonia].

To study pathologic changes in small airways in acute interstitial pneumonia (AI), changes in the terminal or respiratory bronchioles in one patient with AI and in three patients with acute exacerbations of chronic interstitial pneumonia (grouped together as the AI group) were compared to those in five patients with chronic idiopathic interstitial pneumonia (IIP) without acute exacerbation. Specimens obtained during autopsy were examined by light microscopy. In the AI group, mononuclear cells had infiltrated the lumen in 47 (23.7%) of the 198 bronchioles examined, and granulation tissue was found in 101 (51.0%). In the IIP group, no changes were found in 37 (97.4%) of the 38 bronchioles examined. Therefore, mononuclear cell infiltration and granulation tissue are common in the bronchioles of patients with acute interstitial pneumonia, but not in those of patients with chronic interstitial pneumonia without acute exacerbation.

Acute Disease↗
PubMed1995

[Small airway obstruction in patients with idiopathic interstitial pneumonia (IIP)--comparison between acute and chronic types].

Small airway obstruction in patients with acute and chronic interstitial pneumonia was studied. Patients with acute interstitial pneumonia (IP, n = 3), and with acute exacerbation of chronic IP (n = 4) were studied as a group, and were compared to patients with chronic idiopathic interstitial pneumonia (IIP, n = 41). Small airway obstruction was defined on a logarithmic %VC-V25/VC plane, because the V25/VC (an index of both small airway obstruction and decreased lung compliance) depended on %VC. Six of seven patients (86%) with acute IP and 8 of 42 patients (19.5%) with chronic IIP had small airway obstruction (p < 0.01). Small airway obstruction was often seen in acute IP, but was not often seen in chronic IIP.

Acute Disease↗
PubMed1995

[Association of active pulmonary tuberculosis and malignant diseases: a clinical study].

The association of pulmonary tuberculosis and bronchogenic carcinoma has been reported by many authors, however, there are rather few studies about the association of pulmonary tuberculosis and other malignant diseases and how the latter affects the outcome of the former. Between 1980 and 1993, we had in our hospital 104 patients who had both active pulmonary tuberculosis and malignant diseases. Pulmonary tuberculosis was diagnosed at the time or after the diagnosis of malignant diseases in 74 patients, of whom 92% (68 patients) were males and 42% (31 patients) were over the age of 70. There were 23 stomach cancer (31%), and 15 lung cancer (20%). In 11 patients tuberculosis developed after the initiation of radiation and/or chemotherapy. 67 patients could be followed up for more than 6 months after the initiation of chemotherapy for tuberculosis and the negative conversion rate was as high as 95.5% at 3 months. The fact indicates that the association of malignant diseases does not influence the course of tuberculosis and that these patients could be treated safely in general hospitals, provided the diagnosis is made properly without unnecessary delay.

Adult↗
PubMed1995

[Long-term study of patients with sequelae of pulmonary tuberculosis after pneumonectomy--obstructive impairment and its causes].

Changes in pulmonary function, chest X-ray films, and CT were retrospectively studied in patients with sequeae of pulmonary tuberculosis 30 years after pneumonectomy (PNX). Over more than 10 years, VC and FEV1% changed at a rate of 23.2 +/- 8.8 ml and 0.683 +/- 0.688% per year, respectively. In the patients studied 30 years after PNX (N = 30), VC was 900 +/- 210 ml, %VC 31.6 +/- 8.1%, and FEV1% was 67.2 +/- 6.8%. About half of these patients had mild airway obstruction. FEV1% was negatively related to the distance from the hilum to the diaphragm on the mid-clavicular line (on the chest films) divided by body height (r = -0.607). Therefore, we think that the airway obstruction may be due to overextension of the bronchi of middle and lower lobes. Emphysema was not found in 18 patients who had no sign of hyperinflation or herniation of the remaining lung to the PNX side on their CT, but it was found in one patient with these signs.

Adult↗
PubMed1995

[Long-term study of patients with pulmonary tuberculosis sequelae after bilateral thoracoplasty-airway obstruction and its causes].

Chest roentgenograms and results of pulmonary-function tests in patients with pulmonary tuberculosis sequelae 30 years after bilateral thoracoplasty were studied retrospectively to detect airway obstruction in these patients and to determine its causes. For periods of more than 10 years, vital capacity (VC) changed at a rate of 15.5 +/- 5.0 ml/year, and forced expiratory volume in one second as a percent of VC (FEV1%) changed at a rate of 0.546% +/- 0.380% per year (n = 13). Thirty years after thoracoplasty, the VC was 920 +/- 180 ml (%VC = 28.4% +/- 5.3%), and the FEV1% was 66.2% +/- 13.7% (n = 21). Thus, mild airway obstruction was found in about half of the cases. For each patient, the distance from the hilum to the diaphragm was measured along the mid-clavicular line on the side with fewer ribs resected, and this distance was divided by the patient's height. The results of that computation was found to be significantly and negatively related to FEV1% (r = -0.681, which suggests that longer bronchi in the lower and middle lobes on that side were associated with lower values of FEV1%. These findings are similar to those in patients with pulmonary tuberculous sequelae after total pneumonectomy. Over an average of 26 years, scoliosis, the vertebra showing the most bending, the intrapulmonary lesion, and the position of the diaphragm did not change, but the cardio-thoracic ratio increased.

Adult↗
PubMed1994

Malunited Colles' fracture. Analysis of stress distribution.

To try to explain disability in the wrist after malunited Colles' fractures, an experiment was designed to evaluate pressure distribution through the wrist joint with varying degrees of angulation of the distal radius. The results of computer simulation analysis of stress concentration using finite element methods were compared with those of pressure distribution studies on the radial articular surface of cadaveric radii in various positions using pressure-sensitive film. Stress existed in volar regions of the radio-lunate joint under normal pressure in the neutral position, but shifted to dorsal regions of the joint, and was concentrated when dorsal angulation reached 30 degrees. We believe that concentrated loads result in pain and may lead to early degenerative joint disease. Early additional reduction of a displaced fragment or a post-fusion osteotomy should be considered when dorsal angulation exceeds 30 degrees in malunited distal radial fractures to decrease abnormal loading across the wrist joint.

Adolescent↗
PubMed1994

Computer simulation analysis of fracture dislocation of the proximal interphalangeal joint using the finite element method.

Stress is a proximal interphalangeal (PIP) joint model was analyzed by the two-dimensional and three-dimensional finite element methods (FEM) to study the onset mechanisms of the middle phalangeal base fracture. The structural shapes were obtained from sagittally sectioned specimens of the PIP joint for making FEM models. In those models, four different material properties were given corresponding to cortical bone, subchondral bone, cancellous bone and cartilage. Loading conditions were determined by estimating the amount and position of axial pressure added to the middle phalanx. A general finite element program (MARC) was used for computer simulation analysis. The results of the fracture experiments compared with the clinical manifestation of the fractures justify the applicability of the computer simulation models using FEM analysis. The stress distribution changed as the angle of the PIP joint changed. Concentrated stress was found on the volar side of the middle phalangeal base in the hyperextension position, and was found on the dorsal side in the flexion position. In the neutral position, the stress was found on both sides. Axial stress on the middle phalanx causes three different types of fractures (volar, dorsal and both) depending upon the angle of the PIP joint. These results demonstrate that the type of PIP joint fracture dislocation depends on the angle of the joint at the time of injury. The finite element method is one of the most useful methods for analyzing the onset mechanism of fractures.

Aged↗
PubMed1990

[The removal efficiency of beta 2-microglobulin, alpha 1-microglobulin and alpha 1-acid glycoprotein by using dialyzers in the bloodstream and transference of endotoxin through membranes].

Retention of beta 2-microglobulin (beta 2-MG) has been indicated as one of the causes of hemodialysis-associated amyloidosis. Membranes with higher permeability (high-performance membrane) have recently been developed accordingly. Several dialyzers were tested by us in an attempt to study their removal efficiency of beta 2-MG and higher molecular substances of alpha 1-microglobulin (alpha 1-MG) and alpha 1-acid glycoprotein (alpha 1-AG), as well as transferring of endotoxin (ET) through membranes into bloodstream. The membranes subjected to our study were PMMA, CTA, PS, EVAL-C and CA. Removal efficiency of beta 2-MG through EVAL-C and CA was lower as compared with that through other membranes (P less than 0.05), while the EVAL-C showed relatively higher removal efficiency for alpha 1-MG and alpha 1-AG. Permeability for ET was not observed with all membranes studied herein.

Alpha-Globulins↗
PubMed1990

[A method to predict pulmonary blood flow by nitrous oxide washout curve].

The study was performed to obtain a relationship between the pulmonary blood flow and the tau b (time constant) calculated from multiple-breath nitrous oxide (N2O) washout curve. Elimination of N2O depends on pulmonary blood flow and alveolar ventilation. From the theoretical consideration, tau b can be calculated by the following formula; tau b = Vd[1/Qt-Qs) + 0.47/VA) Vd = N2O volume of distribution in the body Qt = cardiac output, Qs = shunt blood flow VA = alveolar ventilation. Relationship between observed Qt-Qs and observed tau b was admitted to the predicted formula. The method was compared with the thermodilution method in almost simultaneous measurement of the cardiac output. A good correlation was obtained between them (r = 0.87). Washout curve of nitrous oxide can be used for a reliable measurement of pulmonary perfusion.

Adult↗
PubMed1990

[Disturbance of the autonomic nerve system in patients with chronic renal failure--represented by variation coefficient of R-R intervals in the ECG as a parameter].

Autonomic nerve dysfunction in patients with chronic renal failure has of late become an issue to be investigated. R-R intervals in resting electrocardiograms were measured to evaluate activities of the cardiac parasympathetic nerve system. A total of 140 patients with chronic renal failure were studied to be compared with 20 normal controls (cont.) and 39 with diabetes mellitus (DM). Of these patients 15 were subjected to conservative treatment (CRF), while 125 patients were undergoing hemodialysis due to chronic renal failure-100 of them derived from chronic glomerulonephritis (HD) and 25 from diabetes mellitus (DM.HD). The variation coefficient of the R-R interval (CVRR) was measured after the subject patients had rested for over 15 minutes before a dialysis session. The mean CVRR were 2.15 +/- 1.25% in CRF group, 2.36 +/- 1.37% in HD and 1.37 +/- 0.99% in DM.HD. These values were significantly lower than in control group (4.70 +/- 2.64%). On the other hand, the value in DM.HD group, as shown above, was significantly lower than in HD. In CRF group the CVRR values lowered as residual renal functions decreased. No significant correlations between CVRR S and the duration of hemodialysis treatment were noted among the groups. In HD group the CVRR S were significantly lower in patients with hypotensive tendency during hemodialysis than in those who enjoyed good control of blood pressure. These results suggest that the measurement of CVRR S can be of help in evaluating autonomic nerve dysfunction in patients with chronic renal failure.

Adult↗
PubMed1989

[Hyperamylasemia in acute exacerbation in patients with chronic respiratory failure].

Serum amylase level was examined in 129 cases (225 episodes) of chronic respiratory failure at acute exacerbation, and in 59 cases (62 episodes) of pneumonia without respiratory failure as a control. Cases accompanying diseases, such as acute pancreatitis, parotiditis, ileus, and renal dysfunction, which were expected to develop hyperamylasemia were excluded. The 225 episodes were divided according to the cause of acute exacerbation into 4 groups: pneumonia, bronchitis, right heart failure without infection, and others (e.g. hemoptysis). Hyperamylasemia (greater than 400 S-U) was observed in groups of pneumonia (15/40 = 35.5%) and of bronchitis (12/95 = 12.6%) respectively, but not in those of right heart failure without infection (0/73 = 0%) and others (0/17 = 0%). As a result, hyperamylasemia was found only under conditions of inflammation of lung parenchyma and bronchi with acute exacerbation of respiratory failure. On the other hand no hyperamylasemia was observed in 62 episodes of only pneumonia without respiratory failure. It was concluded that both respiratory tract infection and acute respiratory failure are necessary factors for development of hyperamylasemia originating from lung or bronchi.

Aged↗
PubMed1970

[Rubella].

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Arthritis↗