The mutant 'little' (lit/lit) mouse is deficient in growth hormone and has correspondingly low levels of serum somatomedin. Injection of these mice with human or bovine growth hormone significantly r(l.ises serum somatomedin levels within 6 h. In vivo uptake of radioactive sulfate by costal cartilage in lit/lit mice is similar to that of normal mice, which is unexpected in view of the low levels of circulating somatomedin. If costal cartilages from normal and lit/lit mice are preincubated in medium 199 in vitro before transfer to fresh medium containing radioactive sulfate and serum, there is no consistent difference in uptake of sulfate, demonstrating similar endogenous cartilage activity. In contrast, omission of the preincubation step reveals a lower uptake of sulfate in vitro by cartilage from lit/lit mice as compared with normal mice. Cartilage removed from lit/lit mice 24 h after injection with growth hormone, however, takes up greater amounts of sulfate than cartilage from untreated normal mice. ' Taken together, these data suggest that the level of circulating somatomedin is not a dominant factor in controlling the uptake of radioactive sulfate into costal cartilage of mice in vivo. This calls into question the relationship between somatomedin levels, in vivo rates of sulfate incorporation and rates of growth.

Scanning and transmission electron microscopy were used to study the progressive disruption of Merino wool during the vigorous agitation of the fibres in aqueous 10J0 (w Iv) solutions of sodium dodecylsulfate (SDS). In contrast to the general disruption observed when wool was vigorously agitated in formic acid, the cuticle was slowly stripped from the fibre with virtually no release of cortical material unless prolonged periods of agitation were used. A similar type of disruption took place in aqueous 10J0 (w Iv) solutions of cetyltrimethylammonium bromide (CETAB) and Triton X-lOO. After the agitation in 10J0 (w/v) SDS solution, the released cuticle fragments and the remaining fibres were examined. Only a minority of the cell portions constituting the cuticle fragments had been cleaved within the endocuticle. Often, the fragments included portions from more than one cuticle cell, with the cell junctions still intact. An understanding of the disruptive process was facilitated by the frequent observation, on residual fibres, of low ridges on exposed underlying cuticle cells. These low ridges corresponded with the distal edges of the originally overlying cuticle cells. Amino-acid analysis and scanning electron microscopy performed on preparations of cuticle obtained in solutions of the above detergents and in formic acid indicated close similarities between all of the cuticle preparations.