Rat submandibular and sublingual gland fragments 2 mm thick were immersed in 0.5% (0.025 W ) cyanuric chloride in anhydrous methanol containing 1% (0.1 M) N-methyl morpholine at 23-27 C. After 18-24 hr, the tissues were washed in methanol, cleared in xylene, embedded in paraffin and sectioned at 3-8 p. These tissues were compared with those fixed in: (1) 10% aqueous cold neutral buffered formalin, (2) anhydrous cold methanol,(3) 0.5% (0.014 M) cetylpyridinium chloride in 10% neutral buffered aqueous formalin, and (4) 0.4% (0.015 M) 5-aminoamidine in 50% aqueous ethanol. Tissues fixed in cyanuric chloride were well preserved with little loss or alteration of tissue components, particularly of epithelial mucins and serous components, in contrast to the p r preservation seen with the other fixatives. Tissues were examined by phasecontrast or following staining with Alcian blue 8GX and colloidal iron methods for complex acidic carbohydrates, and, the periodic acid8chiff method for carbohydrates rich in vicinal hydroxyl groups. Dyes such as orange G, aniline blue and phosphotungstic acid-hematoxylin, which do not color or are not specific for carbohydrates, were also used to reveal structural differences resulting from the various methods of fixation. The cyanuration technique is simple to perform, reproducible and safe.
A cylinder of gelatin containing silver spongy granules was placed in and lay within the masseter muscle, the periosteum, and the mandible, and terminated in the medial pterygoid muscle of young (3 month-old) growing miniature pigs. On the basis of an animal sacrificed one week after placement of the cylinder, it was found that the suspending gelatin was removed by cellular activity. Nine months later the remaining animals were sacrificed. Periodic X-rays were taken during the course of the experiment. After sacrifice, the mandible and associated tissues were histologically examined. The results of this study suggest that the silver granules in the muscles maintained their location during growth; the silver granules in the mandible moved forward with mandibular growth. "Slippage" appeared to occur external to the fibrous layer of the periosteum; the site of movement was revealed by the trail of the silver granules. The described method should prove of value in studying the growth interrelationships between bone, periosteum, and muscle.
We studied hearts in which hypertrophy was caused by both pressure and volume overload. Pressure hypertrophy was induced by an aortic constriction; volume hypertrophy was induced by an iron-copper deficiency (anemia). The ventricular weight was increased by 34% in the pressure-hypertrophied hearts at the end of 6 weeks. The ventricular weight was increased by 54% in the volume-hypertrophied hearts at the end of 3 months. A potassium arrest-formalin fixation technique was used to produce a "diastole-like" ventricle. In the pressure-hypertrophied ventricle, the ventricular wall thickness and external radii were significantly increased, whereas the valve-to-apex distance and internal radii remained unchanged. We also found that in the volume-hypertrophied ventricle there was an increase in the valve-to-apex distance, external radii, internal radii, and wall thickness. Although external and internal dimensions increased, the ventricular shape did not change significantly in the volume-hypertrophied ventricle.
The orientation of the muscle fiber bundles within the mammalian left ventricle was examined in a variety of mammals. The hearts were arrested in situ in animals with an intact thorax by means of an isotonic K+ solution perfused via the aorta and coronaries. The hearts were then fixed by formalin perfusion through the same vessels and the hearts embedded in gelatin. Serial sections were prepared perpendicular to the Apex-Valve axis. On close examination, the muscle fibers show the change in orientation from endocardium to epicardium previously described by others. In addition, the clefts and voids of the inner one-third to inner one-half of the left ventricular wall add another dimension to the fiber direction: the fiber bundles appear to take a curving course from the middle of the wall to the endocardial surface. This pattern was visible in all studied hearts. Speculations are made on the significance of this anatomic arrangement.
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