Comparative development of thoracic intervertebral discs and intra-articular ligaments in the human, monkey, mouse, and cat

Developmental features of thoracic intervertrebral discs and their association in the adult with other vertebral structures were investigated in four species. The human anulus fibrosus, nucleus pulposus, and intra-articular ligaments were compared to those of the fetal rhesus monkey, mouse, and kitten. Photomicrographs of transverse sections of intervertebral discs document the presence of intra-articular ligaments in fetuses of these four species. Both transverse and sagittal sections of kittens were used to identify the intercapital ligament as it differentiated from the dorsal part of the intra-articular ligament. Relatively frequent dorsal herniation of the thoracic nucleus pulposus in humans may be due to the vestigial nature of the human intra-articular ligament. Quadrupeds have well-developed intra-articular ligaments, which explains anatomically the paucity of dorsal protrusions of the nucleus pulposus into the vertebral canal in the thoracic region of the cat and mouse when compared to the human. The intra-articular ligament was closely associated with the developing prenatal mammalian intervertebral disc in the four species studied, and this relationship and its surgical importance are described.

Respiratory bronchiolitis following long-term ozone exposure in bonnet monkeys: a morphometric study

To quantitate the response of respiratory bronchiolar (RB) epithelium and peribronchiolar connective tissue (PCT) to chronic exposure to high ambient levels of ozone, two groups of 8 adult male bonnet monkeys each were subjected 8 h daily for one year to 0.64 ppm (UV standard) ozone or filtered air, respectively. Blocks of tissue selected throughout the lung and from first generation RBs following airway microdissection had the following significant exposure-related changes: 57% greater volume of RB in the lung, 27% smaller diameter of RB lumen, 179% thicker media and intima of peribronchiolar arterioles, 61% thicker RB epithelium, and 77% thicker PCT. The increase in thickness of the RB wall resulted primarily from an 84% increase in PCT, with the remainder from the epithelium. Estimates of cellular numerical density showed an 81% increase in cuboidal bronchiolar cells and an 87% decrease in type 1 pneumocytes in the exposed group. Cell volumes from serial section reconstruction showed significantly larger cuboidal bronchiolar (79%), ciliated (117%), and type 2 (66%) cells over controls. Significant PCT changes included more amorphous extracellular matrix (288%), neutrophils (1523%), and lymphocytes/plasma cells (307%). The number of fibroblasts and the volume of extracellular fibers were larger than control values by 44% and 31% in the exposed group, but these changes were not statistically significant. Centriacinar changes due to exposure to long-term, high ambient ozone in bonnet monkeys results in narrowing of respiratory bronchioles primarily by peribronchiolar inflammation (inflammatory cells, fibers, amorphous matrix) and secondarily through hyperplasia of cuboidal bronchiolar cells.

The tracheobronchial epithelium of the bonnet monkey (Macaca radiata): a quantitative ultrastructural study

Since there are major differences between the airway epithelium of man and that of common laboratory species, the tracheobronchial epithelium of the bonnet macaque was characterized to evaluate its usefulness as a model for study of human conducting airways. This study compared the light microscopic, scanning electron microscopic, and ultrastructural appearance of epithelium from the posterior membranous and anterior cartilaginous trachea and mainstem bronchus. Population densities, epithelial volumetric densities, and frequency distributions of cross-sectional areas of nuclei were determined for cell types present on electron micrographs. Four epithelial cell types were distinguished by ultrastructural criteria. Basal cells were 31% of the population and were similar to those described in other species. Ciliated cells were also similar to those of other species and composed 41% of the population; their nuclei were larger than those of other cell types. Mucous goblet cells had large numbers of secretory granules with electron-dense cores and a lucent periphery. They were only 8% of the population by nuclear count but composed 20% of the epithelial volume. The fourth cell type had multiple small vesicles containing small amounts of granular material and was termed a "small mucous granule cell." Small mucous granule cells (16% of the population) were present in greater numbers than mucous goblet cells but were a smaller proportion of the epithelial volume (8%). While population densities of cell types determined from transmission electron micrographs did not vary between sample sites, scanning electron microscopy demonstrated longitudinal streaks of secretory cells in the posterior trachea suggesting that regional differences in epithelial organization exist. We conclude that the macaque extrapulmonary airway epithelium differs from published descriptions of laboratory rodents in both cell types present and relative abundance of those cell types. Although detailed quantitative studies of human extrapulmonary airways are not available, the primate airways resemble those of man in both the types of cells present and the complexity of pseudostratification.

A mechanism of synergistic lung damage by ozone and a respirable aerosol

A hitherto unexpected synergism between the oxidant air pollutants ozone or nitrogen dioxide and a respirable-sized aerosol of ammonium sulfate was previously observed during controlled exposures of rats to these substances. In this paper we examine biochemical and morphometric changes in lungs of rats exposed for 3, 7, or 14 days to ozone (0.64-0.96 ppm), with or without an accompanying aerosol (approximately 1 micrometer mass median aerodynamic diameter) of ammonium sulfate (5 mg/m3). After 3 days of exposure to the mixture of pollutants, rat lung macrophage and macrophage precursors (monocytes) were increased 2- to 3-fold, fibroblasts were increased 2-fold, and apparent collagen synthesis rates were increased 2.5-fold, fibroblasts were increased 2-fold, and apparent collagen synthesis rates were increased 2.5-fold, as compared with values from animals exposed to ozone alone. Continued exposure to ozone alone for 7 or 14 days seemed to mimic changes seen at 3 days with the mixture of pollutants. Total number of lesions per lung was the same for ozone exposure with and without accompanying aerosol; lesions were larger in lungs of rats exposed to ozone plus ammonium sulfate. Based on these findings and a review of the literature, a mechanism for ozone-aerosol synergism is proposed. We suggest that the lifetime of free radicals arising from interaction of oxidants such as ozone or nitrogen dioxide with molecules within the lung is increased by either local pH changes or changes in the local sulfate concentration (or both) caused by inhalation of the respirable aerosol.

Centriacinar alterations in lungs of cats chronically exposed to diesel exhaust

This study describes the morphologic changes in the centriacinar regions of lungs following long-term exposure of cats to diesel exhaust. Nine male cats (13 months of age) from a minimal disease colony were exposed to diesel exhaust for 8 hours/day, 7 days/week for 27 months. Eight cats were exposed to filtered air. Following exposure, the animals were killed by exsanguination and the lungs and trachea removed from the chest by thoracotomy, weighed, and fixed via tracheal cannula with glutaraldehyde/paraformaldehyde (550 mOsmoles, pH 7.4) at 30 cm of pressure. Centriacinar regions were selected from fixed tissue, the airways bisected, and complementary tissue halves processed by a large block method for high resolution light microscopy and for scanning electron microscopy. Compared with controls, diesel-exposed cats had lower fresh lung and kidney weights and lower fixed volumes of the right cranial lobe. The volume fractions of pulmonary parenchyma and nonparenchyma were unchanged. Epithelium of terminal and respiratory bronchioles in exposed cats consisted of three types of cells (ciliated, basal, and Clara cells), compared with only one type (Clara cells) in controls. Carbon-laden macrophages were found filling alveolar and interstitial spaces in exposed animals. Type 2 pneumocyte hyperplasia was present in proximal interalveolar septa. More distal alveolar ducts and the majority of the rest of the parenchyma were unchanged from controls. We concluded that exposure to diesel exhaust produces changes in both epithelial and interstitial tissue compartments and that the focus of these lesions in peripheral lung is the centriacinar region where alveolar ducts join terminal conducting airways.

Coronary collateral development in the rhesus monkey (Macaca mulatta)

The ability of the rhesus monkey to form coronary collaterals was tested in ten animals. Ameroid constrictors were implanted on the left circumflex coronary artery and allowed to remain for 12 weeks. One animal died of an acute myocardial infarction nine days after surgery; the remaining animals survived without clinical signs referable to myocardial ischemia. The hearts were excised at 12 weeks postsurgery for perfusion fixation and coronary vascular injection with barium-gelatin. All hearts exhibited infarction scars in the circumflex-perfused regions, with infarcts varying from a transmural scar to cases with a thin margin of surviving myocardium at the epicardial surface. Coronary collaterals were infrequent and small in size, and particularly evident in the atria. We conclude that the rhesus monkey is unable to develop sufficient coronary collateral blood flow to prevent myocardial infarction after gradual, total coronary occlusion with ameroid constrictors.

Synergistic effects on rat lungs of mixtures of oxidant air pollutants (ozone or nitrogen dioxide) and respirable aerosols

A hitherto unexpected synergism between the oxidant air pollutants ozone or nitrogen dioxide and a respirable-sized aerosol of ammonium sulfate was observed during controlled exposures of rats to these substances. Response of rat lungs to these pollutants was quantitated by measurement of apparent collagen synthesis rates in vitro by lung minces from exposed animals. Dose-response curves to either O3 or NO2 were altered in the presence of 5 mg/m3 of (NH4)2SO4 aerosol. Morphometric and histologic observations of lungs from rats exposed to high levels of ozone, with and without concurrent exposure to the (NH4)2SO4 particles, confirmed such synergistic effects. In a separate set of experiments, rats were exposed at near ambient levels to mixtures of ozone and sulfuric acid aerosol (submicron-sized aerosol). Potentiation of ozone effects on lung collagen synthesis rates was also observed in these experiments. These observations may have broad implications for the appropriate evaluation of laboratory data in the setting of ambient air quality standards and/or threshold limit values for occupational safety.

Morphometric estimates of infiltrative cellular changes during the development of bleomycin-induced pulmonary fibrosis in hamsters

The sequence of cellular infiltration into interstitial lung tissue subsequent to intratracheal administration of bleomycin was examined in hamsters. Quantitation of lesions following bleomycin treatment showed a transient increase in the percentage of lung involved, which peaked at 21 days and decreased thereafter. Associated with these lesions was a significant increase in interstitial cell profile density at 21 and 28 days. The total number of cell profiles decreased after 28 days. The cellular composition of the lesion was dominated by monocytes, neutrophils, and macrophages in the initial phase of the fibrosis. Subsequently, monocytes were significantly decreased at 21, 28, and 42 days, as compared with the 7-day value. Similarly, neutrophils were significantly decreased at 21 and 28 days, as compared with the 7-day value. In contrast, macrophages were significantly decreased in the initial phase (7 days) of the cellular infiltration and the later phase at 35 and 42 days, as compared with the value at 4 days after treatment. Lesion composition in the later phase exhibited significant increases in fibroblasts and eosinophils, accompanied by a general increase in lymphocytes. It is concluded that bleomycin-induced inflammatory sequela exhibits temporally based changes in cellular composition of the infiltrate and that the temporal changes in cellularity might be one of the determinants in the pathophysiology of pulmonary fibrosis induced by bleomycin.

Morphometry of in situ and lavaged pulmonary alveolar macrophages from control and ozone-exposed rats

Effects of ambient levels of ozone on cell size and compartments were determined morphometrically for both in situ and lavaged pulmonary alveolar macrophages from rats exposed to filtered air or to filtered air with 0.60 ppm ozone. The ozone exposure was 8 hr/day for 3 days. Significant exposure-related compartmental volume density changes of in situ centriacinar macrophages were: decreased endoplasm (p less than 0.01); increased lysosome-like structures (p less than 0.01); decreased primary lysosomes (p less than 0.01); increased small and large secondary lysosomes (p less than 0.001); and decreased phagosomes/autophagosomes (p less than 0.05). In lavaged macrophages, the only significant exposure-related change was an increase in the density of large secondary lysosomes (p less than 0.01). Mean profile areas of in situ centriacinar macrophages from control and exposed rats were 86.94 micrometers2 and 112.04 micrometers2, respectively. The average mean cell volume V and mean caliper diameter D of macrophages lavaged from control rats were 1128.45 micrometers3 and 12.92 micrometers, respectively, whereas those from exposed rats were 1583.08 micrometers3 and 14.46 micrometers, respectively. Exposure-related increases in cell size were seen in both in situ and lavaged macrophages, but more significant differences in cell compartments were seen in the in situ centriacinar macrophages. Morphometry of pulmonary alveolar macrophages after ambient levels of ozone indicated increased uptake, storage, or both rather than cell damage. Comparison of in situ centriacinar and lavaged macrophages from both control and exposed rats revealed significant differences in their volume fractions of nucleus, cytoplasm, ectoplasm, mitochondria, lysosome-like structures, lipid droplets, vacuoles, and phagosome/autophagosomes. These differences between centriacinar and lavaged macrophages indicate different cell populations are sampled by these two methods.

Estimation of cell numbers and volumes of bronchiolar epithelium during rabbit lung maturation

To estimate the numbers and volumes of bronchiolar epithelial cells during lung maturation, we examined rabbits at three time points, 30 days gestation and 4 and 17 weeks postnatal age. Morphometric measures (mean caliper diameter, surface area, and volume) of nonciliated and ciliated bronchiolar cell nuclei, using computer modeling from serial sections, showed a significant decrease in nuclear size for both cell types and a significant increase in cell volume for the nonciliated bronchiolar cell during lung maturation. A shape coefficient (beta) proved to be the most efficient estimator of the number of cells per unit volume when it was used with estimates of the number of nuclei per unit area and the volumetric density of nuclei. Two-dimensional estimates of bronchiolar epithelial cell abundance (the number of nuclei per unit length or area) significantly underestimated the percentage of nonciliated bronchiolar cells as compared to three-dimensional estimates for rabbits 17 weeks of age. We have shown an inverse relationship between nonciliated and ciliated bronchiolar cell abundance during lung maturation. Nonciliated cells decreased while ciliated cells increased. We have confirmed that cytodifferentiation of the nonciliated bronchiolar cell occurs within the first 4 weeks of postnatal development. The volume of the nonciliated bronchiolar cell increased about twofold during development. Because of the concomitant decrease in nuclear volume, the cytoplasm of the cell showed an even greater increase in volume. Within the cytoplasm of the nonciliated bronchiolar cell, glycogen significantly decreased, and agranular endoplasmic reticulum (AER) and mitochondria significantly increased in volume during development. The biosynthesis of AER closely correlated with pharmacological studies of xenobiotic metabolism during rabbit lung maturation.

The in vitro synthesis and degradation of prostaglandins during the development of bleomycin-induced pulmonary fibrosis in hamsters

Subsequent to optimization of conditions for enzyme assay, we examined the in vitro synthesis and degradation of prostaglandins by the lung during the development of bleomycin-induced pulmonary fibrosis in hamsters. It was found that the microsomal protein content on a per lung basis was significantly increased to 144, 129, 134, and 121% of control (2.3 mg protein/lung) at 4, 7, 14 and 21 days post-treatment, respectively. The synthesis of PGD2 was significantly elevated to 10.2, 10.8, and 12.5 nmoles/lung at 7, 21 and 28 days, respectively, as compared to the control value of 5.6 nmoles/lung. Significant increases in PGF2 alpha synthesis from the control value of 3.3 nmoles/lung to 5.2, 8.2 and 5.5 nmoles/lung were found at 4, 7 and 21 days post-treatment, respectively. The synthesis of PGE2 also showed significant increases above the control value of 6.1 nmoles/lung to 10.5, 12.2 and 11.0 nmoles/lung at 7, 21 and 28 days post-treatment, respectively. Similarly, the synthesis of 6-keto-PGF1 alpha was significantly increased to 7.4, 7.5 and 8.6 nmoles/lung at 7, 21 and 28 days post-treatment, respectively, as compared to the control value of 4.4 nmoles/lung. The synthesis of TxB2 was also significantly increased from the control value of 3.9 nmoles/lung to 7.5 and 6.4 nmoles/lung at 7 and 21 days post-treatment, respectively. Accompanying the increased synthesis of prostaglandins in general, the in vitro degradation of PGF2 alpha was significantly increased from the control value of 71.1 nmoles/lung to 173.5, 131.7 and 143.3 nmoles/lung at 2, 4 and 7 days after bleomycin treatment, respectively. We conclude that bleomycin-induced pulmonary fibrosis leads to changes in prostaglandin synthesis and degradation possibly as a result of an accompanying inflammatory response and resident cellular proliferation.

The effect of alpha-difluoromethylornithine on the development of bleomycin-induced pulmonary fibrosis in hamsters

The development of bleomycin-induced lung fibrosis was studied in hamsters drinking tap water or 2% alpha-difluoromethylornithine (DFMO) dissolved in tap water for 14 days. The fibrotic lesions in the lung were evaluated by biochemical measurements of total neutral salt soluble (NSS) and insoluble (NSI) collagens and by morphometric histopathologic techniques. Daily ingestion of DFMO failed to offer any protection against bleomycin-induced lung fibrosis; instead, it increased the deposition of total lung NSI collagen to 396% of control, as compared with 145% of control caused by bleomycin treatment alone. Daily intake of DFMO by itself increased the accumulation of total lung NSI collagen to 250% of control, as opposed to a 145% increase caused by bleomycin treatment alone. Histopathologically, the lung lesions in hamsters treated with bleomycin and DFMO were qualitatively similar to those of hamsters treated with bleomycin alone. However, morphometric estimates revealed that of lung lesions were more diffuse and severe in the former than in the latter group.

Separation and spread of nuclear fragments ("nucleotesimals") in colonic neoplasms

After multiple fragmentation of neoplastic nuclei into "nucleotesimals," a recently discovered variety of amitosis, some fragments appear to be inflated to full nuclear size; other probably lyse, releasing nucleic acid, which may assist in the synthesis of new cytoplasm around newly formed nuclei. This observation may be useful in elucidating one mechanism of neoplastic growth.

Coronary artery distribution in bonnet monkeys (Macaca radiata)

Full use of nonhuman primates as a model for coronary vascular disease has been hampered by several factors, including the limited availability of detailed coronary anatomic data. This study was undertaken to identify the gross coronary arterial anatomy of the Bonnet monkey (Macaca radiata). The hearts of sixteen adult male Bonnet monkeys were subjected to postmortem coronary angiography and gross morphological examination. The main left coronary artery divided into the left anterior descending coronary artery (LAD) and the left circumflex coronary artery (LCA). The posterior descending coronary artery (PDCA) arose from the LCA in 31% of the cases and from the right coronary artery (RCA) in 56% of the hearts. Hearts from two animals (13%) had paired arteries, arising from the LCA and RCA, located in the posterior interventricular groove. The arterial supply to the sinoatrial node originated from the LCA in 69% of the animals and from the RCA in the remainder. The atrioventricular node was supplied by a branch of the RCA in 69% of the animals and from the LCA in the remainder. The coronary anatomy of the bonnet monkey resembles that of man more closely than does the dog in terms of origin of the PDCA, supply of the sinoatrial and atrioventricular nodes, and perfusion of the interventricular septum. The Bonnet monkey may therefore be a useful model for certain specific pathophysiological studies on the coronary circulation.

Colonic adenomas: stereology and growth mechanisms

Stereologic methods were used to determine the amount of growth of colonic adenomatous polyps. Epithelial surfaces were increased from 12 to 226 times compared with the normal mucosa of origin, including the epithelium of the crypts. The number of cells was increased from 12 to 370 times. The supposed villi of the polyps are in reality branched folia, and the crypts between them are slit-like, permitting flow of ingesta through them. The increase in the number of cells is not primarily dependent on mitotic activity but more on amitotic nuclear fragmentation.

Well-differentiated lymphocytic leukemia in a dog: long-term survival without therapy

Well-differentiated lymphocytic leukemia was found during routine hematologic examination of a 12-year-old female poodle with signs of anxiousness, panting and pica. The total white blood cell count was 106,900/microliters and at least 90% of the leukocytes were small, normal-appearing lymphocytes. The dog was examined several times during a 23-month period before it was killed at the owner's request for conditions unrelated to the leukemia. The hematologic picture of the leukemia was essentially unchanged during this time. A deep nuclear cleft was seen in most lymphocytes examined by electron microscopy. Cell surface markers showed most blood lymphocytes to be B-cells. These cells responded poorly to mitogen stimulation.

An elementary introduction to stereology (quantitative microscopy)

Stereology is a branch of applied mathematics used for the three-dimensional analysis of organs and materials from two-dimensional measurements. Stereologic methods are versatile, easily understood, and simply applied. This paper provides anatomists with a practical guide to stereologic techniques and concepts and to ancillary morphometric methods. These methods allow investigators to calculate volume, surface, and numerical densities; make shape determinations; and calculate size distributions for spheres and rotatory ellipsoids. Other topics covered in this article include sampling methods, correction factors for shrinkage and section thickness, index of folding, automated and semiautomated image analysis, and three-dimensional reconstruction from serial sections.

Morphometry of the distal air spaces in lungs of aging dogs

Changes in pulmonary morphometric measurements with age were examined by manual and automated methods in 14 normal beagle dogs aged 289-3,694 days. The study was instituted as a statistical adjunct to previous morphological studies on these dogs that showed anthracosis and associated dilatations in the distal airways in aged dogs. With increasing age, the volumetric density of alveolar ducts increased concomitantly with decreases in the volumetric densities of alveoli and alveolar parenchymal tissue. The numerical and surface densities of alveoli also decreased with age. A comparison of an automated method with accepted manual methods showed no significant differences in stereological measurements of the distal air spaces with the exception of an overestimation of surface density by the automated method. The automated method was found to be a satisfactory method for evaluating the relative differences in alveolar surface densities and the volumetric densities of respiratory air space and parenchymal tissue.