Spinous cells

Mitotic effect. STE, administered to the buccal mucosa of 15 female HMT rats, 6 months of age, weekly for 1 year, produced hyperorthokeratosis, acanthosis, numerous binucleate spinous cells, and subepithelial connective tissue hyalinization. Verrucous carcinoma and squamous cell carcinoma were not seen. Karyotyping revealed that lymphocytes of tobacco-treated, as well as control rats, had normal chromosome number and morphology. However, approx 25% of buccal epithelial cells of the tobacco-treated rats were tetraploid and 5% octa-ploid, compared with only 11% tetraploid and no octaploid in the controls. Results indicated that the mitotic process could be disturbed by tobacco treatment b Molluscicidal activity. Water extract of the dried leaf, at a concentration of 168 ppm, produced equivocal effect on Lymnaea luteola . 

Eighteen cases of an ichthyosiform contact dermatitis caused by antiseptic solutions containing 3% cetrimide and 0.3% chlorhexidine have been reported (5,6). Biopsies showed hyperkeratosis with striking vesicula-tion of lamellar bodies in the granular cells and upper spinous cells, premature secretion of lamellar bodies, and abundant remnants of lamellar bodies and retention of desmosomes between corneocytes. Cetrimide, and not chlorhexidine, was said to be the cause of the dermatitis. 

Etretinate, however, may not completely return the keratinocyte membrane from a psoriatic to a normal state despite clinical improvement. This is based on the failure of etretinate to reduce the greater than normal intramembranous particle density of the fracture face of the protoplasmic half-layer (P face) of the spinous cell plasma membrane in lesional skin after the lesions were clinically resolved (Kitajima and Mori, 1983). 

The dendrites of neurons adjacent to those which degenerate also show extensive growth and sprouting which could facilitate abnormal and disorganised synaptic transmission and cause hyperactivity. It is also known that the dendrites of cells around an alumina focus in monkeys, as well as in human epileptic brain, lose their spinous processes, which might contribute to the paroxysmal discharge by facilitating the spread of depolarisation to the neuron soma. Certainly an increase in the number of Na+ channels on the dendrites of spinal motoneurons, which would facilitate the occurrence of reactive dendritic Na+ spikes, has been seen after axotomy. 

Epidermis. The epidermis is a 50- to lOO-pm-thick layer made of ker-atinocytes that migrate outward from the basal cell into highly differentiated nondividing cells.46,47 During differentiation, keratinocytes transform from polygonal (cuboidal) cells to spinous (prickly) cells, flattened granular cells, and finally to flattened polyhedral dead corneocytes full of the protein keratin.45,47... 

Hyaluronan is most prominent in the upper spinous and granular layers of the epidermis, where most of it is extracellular. The basal layer has HA, but it is predominantly intracellular, and is not easily leeched out during aqueous fixation. Presumably, basal keratinocyte HA is involved in cell cycling events, while the secreted HA in the upper outer layers of the epidermis are mechanisms for disassociation and eventual sloughing of cells. 

Dlugosz, A.A., and Yuspa, S.H., Coordinate changes in gene expression which mark the spinous to granular cell transition in epidermis are regulated by protein kinase C, J. Cell Biol., 120, 217, 1993. 

Among the commercially available 3D skin models suitable for conducting such test and providing sufficient cell proliferation is the EpiDerm (MatTeK Corporation, Ashland, MA, USA). The model is constructed from primary neonatal epidermal foreskin-derived keratinocytes. It forms a multilayer differentiated tissue, which contains the dividing basal cell layer along with spinous, granular, and cornified layers resembling the normal human epidermis. DNA repair mechanism, cell cycle control, and checkpoint mechanisms and metabolism are much more similar to the normal conditions in human than those of transformed cell lines. 

De Bersaques also noted that upper spinous layers have less DNA than the basal layer-j-lower spinous layers this means either that the cells are larger as they ascend and contain more protein or that DNA is being removed from the cells during their ascension, and not just at the granular... 

Fig. 10. Electron micrograph from a 300- xm neostriatal slice incubated for 2 hr before fixation. (Top) Electron micrograph shows a well-preserved neostriatal medium-sized cell and surrounding neurophil. N, nucleus No, nucleolus G, golgi M, mitochondria D and d, dendrite AX, axon. (Bottom left) An electron micrograph taken from the middle layer of the slice demonstrating well-preserved neurophil with many axo-spinous synapses and clear...

Similar lesions with constitution of protmding areas are observed through contact with concentrated acids such as 98 % sulfuric acid. A 4 min exposure is sufficient to get significantly altered epidermis morphology (Fig. 3.22). Strong acan-tholysis makes bubbles at the base of the stratum comeum, observed by areas. In these areas, kera-tinocytes show a net nuclear pyknosis and cytoplasmic alterations, especially in the upper layers. In spinous and basal layers, cells have a significantly pyknotic nucleus with a net acidophilic cytoplasm. 

Figure 11.1 Typical tight junction (ridges on the P face and grooves on the E face) between two cells of the spinous layer (x28 000)...

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