RELATIONSHIPS BETWEEN CELL-PROLIFERATION IN THE FOLLICLE BULB AND DERMAL PAPILLA MEASUREMENTS IN WOOL FOLLICLES FROM NEW-ZEALAND ROMNEY SHEEP DURING DIFFERENT SEASONS

Little information is available on the influence on overall fibre prod uction of either size changes in the follicle bulb or relative changes in bulb structures. Various criteria have been used to quantify the s ize of the germinative tissue zone but none have been assessed for the ir suitability or sensitivity as predictors of bulb cell production an d cortical cell migration. This study investigated the relationships f irstly between the number of replicating cells in the follicle bulb an d various measurements of follicle bulb diameter and areas, and second ly between 3-dimensional extrapolations of bulb measurements and papil la dimensions. The raw follicle data are derived from a companion stud y (Holle et al. 1994) of Romney sheep with two genetically different l evels of wool production examined during periods of low (winter) and h igh (summer) fibre production. Strong relationships existed between si milar measurements (e.g., diameters), but their relationship varied wi th season. Bulb diameter was only weakly related to bulb area and bulb volume, but papilla length was most closely associated with bulb volu me regardless of season or genotype. Correlations between fibre diamet er and inner root sheath (IRS) diameter changed significantly with sea son and no relationship existed between IRS diameter and bulb volume d uring summer. This suggests that the distribution of cells between the IRS and fibre varies with season.