In support of predictions for inhaled particle deposition, morphometric measurements were taken on 20 replica airway casts of people aged 11 days to 21 years. Measurements of right upper lobe airway lengths, diameters, and branching angles were made such that a growth model suitable as input to predictive equations for particle deposition efficiency was obtained. The tracheobronchial airways growth was describable by linear regressions on body length. The length-todiameter ratio of growing airways did not change in any simple way as a function of airway generation. Airflow rates for a given state of physical activity for various ages were found from previously published data to be describable by linear regressions on body mass. Three states of physical exertion-low activity, light exertion, and heavy exertion-were used for modeling purposes. The computed particle deposition efficiencies indicate that under most circumstances smaller (younger) people will have greater tracheobronchial deposition efficiencies than larger (older) people. For example, tracheobronchial dose on a per kilogram body mass basis for 5-pmdiameter particles may be more than 6 times higher in the resting newborn than in the resting adult assuming equivalent deposition efficiencies above the larynx.Because little is known regarding age-related differ-(1913) published values for lengths and diameters (sagences in inhaled particle deposition, we have been inter-ittal and frontal) of the trachea and right and left main ested in developing mathematical predictions for particle bronchi for 12 children aged 1 month to 13 years, and a deposition in the tracheobronchial airways correspond-40-year-old adult. Engel's data show relatively rapid but ing to a range of ages. Such predictions are strongly decelerating growth of the measured structures up to dependent on airway anatomy, so measurements of the about age 7 years, but with only one child over age 10 growing airways were taken to develop a model upon years little can be said about growth after age 7. Also, which to base the mathematical predictions for depo-only two generations of airways were well described. sition.Although there is agreement on the sequence of events Although several investigators have provided quanti-during postnatal lung growth, many fundamental questative descriptions of the dimensions of adult human tions remain. There is general agreement (although perairways, few have described the manner in which these haps a lack of direct proof) that the full number of structures grow. Among the earliest morphometric bronchial airways are present at birth and that alveolarmodels for the complete adult tracheobronchial airways ization of bronchioles continues postnatally in a proxiwere those published by Weibel(1963). To generate these mal direction. Bronchial airway growth generally models, measurements from the trachea downward for parallels changes in stature, but there is confusion reabout 10 generations were made on a plastic replica cast garding details. This state of und...

Rasmussen, et al.anilide (1 g, 6.6 mM) and Pb(0Ac)4 (2 g, 4.5 mM) were stirred together in CH2C1j (50 ml) for 10 min. The reaction mixture was then filtered and steam distilled. The distillate was extracted with CH2C12 to give p-benzoquinone [90 mg, 24% conversion based on Pb(OAc)4 ] characterized by comparison with authentic material, tic, uv, mp 113-114°, and mixture melting point.

Sprague-Dawley rats that had been subjected 2 months previously to partial resection (10 per cent) of thc small intestine and an equal number of control rats were injected with tritiated thymidine and sacrificcd at intervals during the subsequent 16 hours. Segments of duodenum, jejunum and ileum were prestained by the Feulgen technique and radioautographed. ~fhe proportion of crypt cells bearing labeled nuclei, the perccntage of labeled crypt cells in mitosis and the appearance of labeled crypt ceils on the villi were determined. Comparison of control and resected rats showed that (a) the proportion of intestinal crypt cells incorporating thymidine was considerably greater and uniformly high throughout the shortened intestinc, (b) the life cycle of crypt cells was slightly reduced, and was uniform throughout the shortened intestine, and (c) the time during which cells wcre retained in crypts was markedly reduced. On the basis of persistent, generalized increase in the production of crypt cells, and on prior evidence that the epithelial cells of shortened intestine continue to have a brief life span and evidence of metabolic immaturity, the existence of a humoral factor, tentatively called "intestinal epithelial growth hormone," is postulated.As reported previously (1), resection of I0 per cent of the small intestine (removal of 10 cm of ileum) in rats was followed by a pronounced increase in the rate of migration of the epithelial cells covering the villi in the remaining portion of small intestine. Two months after resection, the distance traveled by mucosal cells examined 2 and 24 hours after labeling with tritiated thymidine was increased by approximately 23 per cent in the duodenum, 114 per cent in the jejunum, and 141 per cent in the ileum. The "life span" of epithelial cells in the intestinal mucosa, as estimated from the rate of migration and the height of villi, was decreased to 82, 46, and 42 per cent of normal for duodenum, jejunum, and ileum, respectively.The present study demonstrates that the rate of appearance of new ceils on the intestinal villi is accelerated in proportion to the increased rate of cell migration. Proliferation in intestinal crypts is also increased throughout the small intestine, but this increase is not proportional to the increase in the rate of migration. It is proposed that a growth factor, provisionally called intestinal epithelial growth hormone (IEGH), is released in response to intestinal resection and that this factor accelerates the rate of epithelial proliferation throughout the small bowel. M A T E R I A L S AND M E T H O D SIn a first experiment, the experimental animals consisted of 16 male Sprague-Dawley rats, weighing 300 to 350 gin. A 10 cm portion of the lower ileum, representing 10 per cent of the length of the small intestine, was removed from each at a point about 20 cm 285 on

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Nasal, tracheal and bronchoalveolar injuries resulting from acute ozone exposure of rats were investigated by permeability changes. 99mTc-labeled diethylenetriaminepentaacetate (DPTA) and 125I-labeled bovine serum albumin (BSA) were selectively instilled into localized airway regions of anesthetized rats exposed to 0.8 ppm 03 or clean air for 2 h. Transmucosal transfer of the radiolabeled tracers was detected by counting the radioactivity in blood samples collected at short postinstillation time intervals. Permeability measurements were made on d 0, 1, and 2 after O3 exposure to analyze the extent and persistence of tissue injury in the nasal, tracheal, and bronchoalveolar regions. Normal mucosal permeability was low in nose, intermediate in bronchoalveolar zone, and high in trachea. The O3-related injury, reflected by elevated permeability, was substantial in the trachea and bronchoalveolar zone but was minimal in the nose immediately after the exposure. Abnormal permeability persisted for less than 24 h in the trachea but for more than 24 h in the bronchoalveolar zone. The results are consistent with the properties of O3 of causing greater injury in the smaller airways and the alveolar zone than in the trachea.