Control of animal cell proliferation

Present understanding of the control of animal cell proliferation is summarized briefly. Major gaps in present knowledge are listed. Models of growth control are discussed.     

Peptidergic regulation of secretory activity in amphibian olfactory mucosa: Immunohistochemistry,neural stimulation,and pharmacology

Summary The role of substance P in the regulation of secretion from sustentacular cells, Bowman's glands and deep glands in the amphibian olfactory mucosa was investigated using immunohistochemical, electrophysiological, and pharmacological methods. Substance P-like immunoreactive varicose fibers extended through the olfactory epithelium, terminating at or near the surface. In addition, immunoreactive varicose fibers innervated Bowman's glands, deep glands, and blood vessels in the lamina propria. Innervation of Bowman's gland was sparse, with fibers terminating on basal acinar cell membranes; deep gland innervation was abundant, with fibers often extending between acinar cells almost to the lumen. Stimulation of the ophthalmic branch of the trigeminal nerve resulted in slow potentials recorded at the surface of the olfactory epithelium. When the olfactory mucosae from trigeminal-stimulated animals were examined histologically, morphological signs of secretory activity were observed, suggesting that substance P was released from the trigeminal nerve terminals. Topical application of 10^-5 to 10^-3 mol substance P resulted in morphological signs of secretion that were very similar to those seen as a result of trigeminal stimulation. Thus, substance P released from trigeminal fibers may modulate secretory activity within the olfactory mucosa.     

High frequency force generation in outer hair cells from the mammalian ear

Mammalian outer hair cells generate mechanical forces at acoustic frequencies and can thus amplify the sound stimulus within the inner ear. The mechanism of force generation depends upon the plasma membrane potential but not upon either calcium or ATP. Forces are generated in the lateral cortex along the full length of the cell. The cortex includes a two-dimensional cytoskeletal lattice composed of circumferential filaments 6-7 nm thick that are cross-linked by filaments 3-4 nm thick and 40-60 nm long. The two filament types may, respectively, be actin and some form of spectrin. The lattice reinforces the cylindrical shape of the cell and permits limited changes in length. Beneath it lie the lateral cisternae, a regular system of multi-layered membranes. Force-generation may depend upon voltage-dependent shape changes in proteins that lie either in the plasma membrane or in the cytoskeletal lattice.     

Factors influencing the growth of alveolar type II epithelial cells isolated from rat lungs

Primary cultures of isolated alveolar type II cells have been established. Under appropriate conditions, these epithelial cells can be subcultured at least nine times. Using standard assay procedures, effects of growth factors or inhibitors can be studied. The alveolar type II cells show a marked response to both serum and growth factors in tissue culture. Either epidermal growth factor (EGF) or human urine gives an increase in thymidine incorporation (2-fold and 10-fold, respectively). The growth factor(s) in urine appears to be different from urogastrone (human EGF). The response to urine is several-fold greater than the response to a saturating concentration of mouse EGF alone. Mouse EGF added to urine does not increase the activity of urine. The period during which the alveolar type II cells respond to the growth factor(s) in urine is limited to early passages of the cells. Alveolar type II epithelial cells produce growth inhibitors in culture. Inhibitors are produced in the growth medium in either the presence or absence of serum. The concentrated inhibitor, although very unstable, gives up to a 50% inhibition of thymidine incorporation when assayed on sparse or crowded alveolar type II cells.     

New studies on odour discrimination in the frog's olfactory receptor cells. II. Mathematical analysis of electrophysiological responses

Revial et al. (1982) reported the experimental findings obtainedin cell units stimulated with two new sets of odorants. Thepresent paper deals with mathematical processing of these electrophysiologicaldata. The multidimensionality of the odour space was confirmed.Camphor, isoborneol and cineole appeared to represent a ‘camphorgroup’ markedly discriminated from other odorants. A‘terpenegroup’ including terpinene, dimethylstyrene, limoneneand cymene and related to menthane and menthene was observed.A series of 8 cycloketones was found to have a linear patternin the factorial planes and to be subdivided into three subsets.Cyclooctadecanone and cyclotetradecanone displayed correlationsand spatial relationships with musk ketone while cycloundecanone,cyclodecanone and especially cyclononanone were more relatedto the‘camphor group’. Separate processing of theunitary responses of 12 receptor cells recorded from a singlepreparation led to the building of a factorial space resemblingthat constructed with the full collection of data. The incidenceof odorant concentration on similarity evaluation is discussedon the basis of receptor responses to two different concentrationsof some of the odorants.