Biomedical subjects
Publications and source records attributed to E W Van Lennep.
An examination of human seabaceous glands by transmission electron microscopy has revealed the presence of gap junctions. The junctions are found in abundance between differentiating cells, and annular forms are also seen. The possible significance of this new finding is briefly discussed.
Myoepithelial cells, which occur in many but not all exocrine glands, are usually quite conspicuous in salivary glands. Their contractile nature seems established beyond doubt, and the morphological similarities to smooth muscle cells are close enough to suggest that they contract by a similar, if not the same, mechanism. Morphologically speaking, they seem to possess a dual autonomic innervation, but, functionally speaking, the sympathetic control seems usually to be more important that the parasympathetic. While their contraction undoubtedly causes a transitory increase in the rate of delivery of saliva to the oral cavity, the principal function of the cells seems to be to prevent distension of the endpieces during secretion. This is achieved partly by providing support for the endpiece and partly by a widening and shortening of the intercalated ducts, which has the effect of lowering the outflow resistance.
Centrifuged pellets of turbid parotid saliva from cystic fibrosis (CF) patients and non-CF subjects, obtained from saliva kept at 2 degrees for 10 min, had the electron microscope appearance of amorphous, round particles, and were thought to be colloidal aggregates of organic material. Drops of turbid saliva, from samples incubated for 2 hr at 2 degrees or 37 degrees, additionally contained discrete, electron-dense crystals having well defined angular morphology: usually cubic, retangular, or approximately hexagonal. The inhibitors, urea, guanidine hydrochloride, and EDTA, resulted in no crystals being observed. Selected area electron diffraction from individual crystals showed predominantly hexagonal, rectangular patterns could be indexed as coming from hydroxyapitite. A transition from the hexagonal to the rectangular pattern and back to the hexagonal pattern could be obtained from individual crystals tilted in the electron microscope. The square diffraction pattern may be from octa-calcium or brushite. Polyacrylamide gel disc electrophoresis of the parotid saliva indicated that the sparingly soluble proteins in the 2 degree and 37 degree pellets comprised proline-rich proteins and a calcium-precipitable, trichloroacetic acid (TCA)-precipitable phosphoprotein, which fluoresced with amido schwarz and Coomassie brilliant blue G250.
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