Lung scanning with ^99mTc-MAA was done on five normal man and thirty patients suspected of pulmonary circulatory disturbance and the following results were obtained.
1. Lung scan is readily visualized immediately after intravenous injection of ^99mTc-MAA and its radioisotopic activity reaches maximum concentration at 15-20 seconds on the lung image.
2. Lung scans obtained from normal subjects are almost identical to their lung silhouettes derived from their chest roentgenograms, therefore those scans can be used as controls in comparative studies of patients with abnormal blood flow.
3. All three cases with pulmonary embolism had abnormal scans. In two cases, the chest roentgenogram showed no abnormality, therefore perfusion lung scanning provides very useful technique for the diagnosis of pulmonary embolism as well as angiography. Lung scanning with ^99mTc-MAA is considered to be a first choice because it is less troublesome.
4. Twenty seven cases of focal pulmonary circulatory disturbance (such as emphysema, fibrosis, obstructive lung diseases, destroyed lung, and other abnormal conditions), were also examined, and focal defects in lung scans showed a correlation with chest roentgenographic abnormalities on the whole. Futhermore, ^99mTc-MAA scintigrams may reveal minor pathologic perfusion changes in comparison with roentgenogram.

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The histogenesis of squamous cell carcinoma in the respiratory tract has been researched by many investigators, but experimental approaches to analyse it still have many difficulties. Previously, experimental production of squamous cell carcinomas induced by cigarette smoke in the hamsters upper respiratory tract pretreated by polycyclic aromatic hydrocarbons were studied by us. From these experiments, sequential epithelial changes and the histogenesis of squamous cell carcinoma in the ciliated respiratory epithelium were discussed in this paper.
The first progression of the neoplastic state was characterized by squamous metaplasia, basal cell hyperplasia, pachydermia as well as squamous hyperplasia. In the premalignant phase squamous papillomas, as well as atypical cell downgrowth and carcinoma in situ were seen. The malignant phase showed tumors apparently originating from a common precursor differentiating to typical squamous cell carcinomas. They occured in the same target tissue, late in the course of the experiments. These tumors and precancerous changes closely resembled descriptions of humans exposed to carcinogenic environments.
It was suggested that these experiments offer a good model for morphologic studies of respiratory carcinogenesis similar in development and characteristics to those of the human.

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Available literature substantiates the existence of three mechanisms which could produce bronchoconstriction in human beings: β₂-adrenergic blockade, cholinergic stimulation and α-adrenergic stimulation. The role, if any, of α-adrenergic receptors in producing bronchospasm is presently a point of controversy.
The present investigation was conducted in an effort to clarify the mechanism of α-blocker on the relaxation of guinea-pig trachea (GPT) with various bronchodilators. Male guinea-pigs, weighing 250-300g, were killed. GPT was removed and suspended in a glass chamber and superfused with Krebs-Hensleit solution at 37°C saturated with oxygen and carbon dioxide (95: 5, v/v). Relaxation of GPT was detected by an isotonic transducer and displayed on a polyrecorder.
1) Bronchodilating effects of isoproterenol, salbutamol, clorprenaline, adrenaline and noradrenaline were remarkably increased with continuous infusion of a specific α-blocker, phenoxybenzamine.
2) Bronchodilating effects of prostaglandin E₂ and neophyllin showed almost no change with continuous infusion of phenoxybenzamine.
3) These results suggest the usefulness of the application of an α-blockers in the treatment of chronic obstructive lung disease either by itself or combined with β-stimulators.

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While mountain climbing at high altitude, a 24-year-old male developed pulmonary edema and became semicomatose. This patient was hospitalized and improved upon administration of digitalis and steroids.
On the 21st. hospital day, a localized hemopneumothorax was found, however, the etiology was not determined. Thrombotic and hemorrhagic phenomena in autopsy cases of high altitude pulmonary edema have been described in the literature. These phenomena probably contibuted to the development of hemopneumothorax in this case.

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