Acid phosphatase activity fluctuates in mature epidermal guard cells of Campanula persicifolia in response to changing light conditions. As demonstrated both by Gomori's method and by Burstone's simultaneous coupling azo dye technique in both unfixed and aldehyde-fixed epidermal strips, the enzyme is active in the spherosomes when the guard cells are flaccid and the stomata are either partially or fully closed. It is inactive when the cells are turgid and the stomata are fully open, regardless of whether opening had resulted from a photoactive or scotoactive process. In living preparations, such inactive spherosomes will gradually become active for acid phosphatase if turgid guarde clls are subjected to partial plasmolysis. Marked activity for acid phosphatase becomes manifest in the vacuoles as well as in the spherosomes of the guard cells if the plants are kept in the dark for many days. In senescent leaves the vacuoles of the guard cells are reactive even though the plants are grown in the light. The walls of the epidermal cells exhibit sporadic activity for the enzyme, but the walls of guard cells have not been observed to react. Nuclear staining sometimes is present after tissues are incubated in the Gomori medium, but it is considered to result from nonenzymic binding of lead on the nuclear surface. The spherosomes evidently are among the principal sites for acid phosphatase activity in plant cells. In guard cells the spherosomes are considered to be enzymically active when the cells are in a relatively catabolic phase of metabolism and to become inactive when the cells enter a relatively anabolic phase.
A replicating population of non-monocyte-derived free cells appears in organ-cultured embryonic rat lungs, indistinguishable from alveolar macrophages by classical criteria such as ultrastructure, lysosomal enzyme cytochemistry, and phagocytic behavior. We demonstrate similar events in cultured embryonic hamster lungs and development of macrophage-associated properties on the plasmalemma of these cells in both species. Immunoperoxidase localizations were obtained using monoclonal antibodies against alveolar macrophage antigen (HAM1) in hamsters, and rat macrophage antigen (ED1) and leukocyte-common antigen (OX1) in rats. Fc and C3b receptors were identified in both species by immune rosetting. HAM1 staining, perinuclear in rare cells at explantation, gains definitive surface localization 3-4 days later as cells prepare to emerge through the pleura. ED1 and OX1 cytoplasmic staining first occurs after 24 hr, increases as macrophages multiply and congregate beneath the pleura, and translocates to the plasmalemma of emerged cells. Some glass-adherent cells from lung explants have Fc receptors. The proportion rises sharply for 24 hr and equals fully emerged cells (90-95%) by days 3-4. At first phagocytosis is slow to follow Fc receptor binding, but ingestion time decreases to 3-10 min as macrophages mature. A minority of emerged macrophages bind complement-opsonized erythrocytes, which are rarely taken up. These properties are shared by alveolar macrophages of adults.
Small granule epithelial cells and clusters of these cells termed neuroepithelial bodies are widely distributed in the respiratory systems of vertebrates, according to observations made in 24 speci...
Autoradiographs were prepared from lungs of a newborn Syrian golden hamster exposed continuously to [3H]thymidine throughout the final 4.5 days of gestation. Silver grains were counted over nuclei of 1,145 nonendocrine airway epithelial cells adjacent to 28 mature neuroepithelial bodies (NEBs). Generally, accumulated label was greater in cells nearer a NEB than in those further away. Diminution of label with increasing distance from the closet NEB was confirmed statistically. In 24 of 28 instances, both rank-order correlation and linear regression were significant (P less than 0.001-0.05); in two others, only one test was significant; in another two, neither test was significant. The pattern was consistent and widespread. Rank-order correlations and linear regressions were significant (P less than 0.001) in populations pooled separately from left lung, right upper, and right lower lobes, and the three regression lines were superimposable. Confirmation was obtained in another animal by labeling S-phase cells with a 2-h transplacental pulse of bromodeoxyuridine (BrdU) on fetal day 15. Of 322 BrdU-positive cells counted in 270,204 microns 2 of bronchial epithelium, 174 (54%) lay within 20 microns of a neuroepithelial body. This concentration of dividing cells was significant by chi-square test: chi 2[1] = 101.62; P less than 0.001. We conclude that established NEBs promote growth of the developing airway by stimulating proliferation of local endoderm. A few daughter cells may enter NEBs; most move away to join the expanding nonendocrine airway lining.
The development of both rudimentary cilia and the ciliated epithelial border has been studied in organ cultures of rat lungs that have absorbed 1100 rads of X-radiation 24 hours after explantation. The radiation was administered 1 to 5 days before the appearance of the earliest precursors. No delay was observed in the appearance of the ciliated border, and no reduction in the number of cilia was seen in the irradiated cultures as compared to controls. Electron micrographs demonstrated that ciliogenesis proceeded normally both from centrioles present at the time of irradiation (rudimentary cilia) and from basal bodies still unformed when the X-rays were given (the ciliated border). Apparently basal body formation and maturation progress normally even though the cell is irradiated with a dose that leads to proliferative failure.
Abstract Earliest origins of macrophage populations in the central nervous system, the liver, and the lungs were studied in rat embryos aged between 10.5–11 days and 14 days of gestation, based on light and electron microscopic identification of macrophages using peroxidase‐coupled isolectin B 4 of Griffonia simplicifolia (GSA I‐B 4 ), which recognizes alpha‐D‐galactose groups on the cell membrane. During embryonic life macrophages and their precursors are GSA I‐B 4 ‐positive and generally bereft of peroxidase‐positive granules. At 10.5 days the yolk sac and embryonic circulations have just become joined, the brain has five vesicles but nerve cells are little differentiated, the liver exists as a diverticulum of the gut with fingerlike extensions of hepatocytes, and the lungs as a laryngotracheal groove . Macrophages and/or their precursors occurred in small numbers in embryonic mesenchyme and blood vessels but showed no special affinity for either liver or lung rudiments. The developing brain was the first organ to be colonized, beginning on prenatal day 12. The liver followed between days 12 and 13 and was succeeded by the lungs, beginning between days 13 and 14. Dividing macrophages were present in these organs at the outset of colonization and throughout the duration of the embryo series, indicating that from the beginning, replication of resident cells contributes to growth of the local population. Granulocyte precursors were first apparent in the liver around day 13; they are also GSA‐positive but are distinguished from macrophages by their content of peroxidase‐positive granules. Organ cultures of 13‐day liver and lungs, and 14‐day brain tissue, indicate that whereas isolated liver fragments support the formation of both granulocytes and macrophages, only the latter develop in brain or lung cultures. A resident population of macrophages evidently is set up very early in these organs, well before white cells colonize the spleen, bone marrow, and other future blood forming regions. The events outlined are seen as stages in an embryo‐wide process that leads to establishment of macrophage populations in various organs.
