Open AccessTime‐dependent effects of removal of the pars distalis of the pituitary gland on toad epidermal cell and tissue kinetic parameters
Author(s) -
Budtz Povl E.
Publication year - 1982
Publication title -
cell proliferation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.647
H-Index - 74
eISSN - 1365-2184
pISSN - 0960-7722
DOI - 10.1111/j.1365-2184.1982.tb01573.x
Subject(s) - toad , medicine , endocrinology , biology , epidermis (zoology) , hormone , mitotic index , metaphase , bufo , amphibian , pituitary gland , proliferation index , moulting , mitosis , cell growth , anatomy , microbiology and biotechnology , biochemistry , chromosome , larva , botany , gene , ecology
. Amphibian moulting and its hormonal control has been extensively studied, but the possible influence of hormones on epidermal proliferation has been less investigated. In the present contribution to studies on the control of epidermal homeostasis, the proliferative pattern of the toad epidermis following ablation of the pars distalis of the pituitary gland is analysed by an investigation of the changes in the epidermal cell number, metaphase index and [ 3 H]thymidine incorporation at various times after the operation. During the first 24 hr after pars distalis ablation, labelling index (LI) increased concurrently with an initial decrease in the metaphase index (MI), followed by an increase. During the same period of time the mean grain count (MGC) and the grain distribution pattern also changed. From 24 hr to 7 days after operation, MI, LI, and MGC were significantly lower than those of controls, but increased to control levels at 14 days after the operation. Phase durations and their possible changes were not measured directly, but data showed that the S‐phase duration (Ts) and the mitotic duration (TM) must have changed in relation to each other during the experiment. Assuming that the MGC is a rough estimate of the DNA‐synthesis rate, the compatibility of a postulated change in phase duration with the observed MGC was analysed. This analysis revealed that TS and TM could have decreased up to 18 hr after the operation, whereas these phase durations, after 24 hr and during the rest of the experiment, increased compared to those of controls. Even with these possible changes in phase durations, and in the absence of direct assessment of cell division rates, the observed cell kinetic parameters appeared incompatible with an increased rate of proliferation. This was surprising since the efflux of cells from the living, subcorneal epidermis to the stratum corneum was significantly increased after pars distalis ablation, without a concurrent decrease in the stratum corneum recruitment cell pool (SCRP‐number of subcorneal epidermal cells per mm surface). Possible reasons for the discrepancy between the expected increase in proliferation following pars distalis ablation, and the failure to demonstrate this, are discussed.