Rats of non-pure strain were allowed to drink N-Methyl-N-Nitro-N-Nitroso-guanidine (MNNG) solution (200-250 micrograms per milliliter) ad libitum. After 14 months, in addition to MNNG, each of them was fed with 1 ml of saturated NaCl solution once a week. During a period of 18 months, there were 5 cases of gastric adenocarcinoma and 2 cases of adenocarcinoma of the duodenum among 18 experimental rats. Besides, there were a few cases of papilloma of the fore-stomach and carcinoma of the lung. In 17 control rats, no tumors of the gastro-intestinal tract were seen. Microscopic examination of the mucosa of the pyloric gland region of the stomach in the experimental rats showed that the deep epithelial cells of the gastric pit exhibited a marked degree of proliferation and a malignant change had started in these cells. Electron microscopic observation of these epithelial cells revealed that the the proliferating cells showed only increased nucleocytoplasmic ratio, while those with atypical hyperplasia showed that the form of the nucleus and the changes in the basement membrane and intercellular junctions were somewhat similar to those of malignant cells. It is believed that increase in concentration of the carcinogens and prolongation of the time of contact with them may induce malignant tumors in the insensitive animal.

Adenocarcinoma↗

PubMedDate not supplied

Development of a new left ventricular assist device: the dynamic aortic valve.

We have been developing a new left ventricular assist device, an axial flow pump implanted at the aortic valve position. Since the device is intended for long-term use, its motor unit and pump are physically separated. The device consists of a "rotor-impeller" and a support cage. The rotor joins the impeller at one end and provides torque needed to spin the impeller. The support cage consists of a cantilever, a cantilever shaft, a top ring, and an end ring. The support cage is designed to fit within the ascending aorta and sutured to the aortic annulus during implantation. The magnetic rotor will rotate in the presence of alternating magnetic fields generated by an electric motor. The assembly also serves as a valve by maintaining the appropriate pressure drop across the aortic orifice. A prototype device was fabricated and tested in vitro. It produced a flow rate up to 5 L/min with a rotation rate of 12,600 rpm at a pressure difference of 100 mm Hg. The results proved the feasibility of the new device.

Aortic Valve↗