Dynamic injury tolerances for long bones of the female upper extremity.

This paper presents the dynamic injury tolerances for the female humerus and forearm derived from dynamic 3-point bending tests using 22 female cadaver upper extremities. Twelve female humeri were tested at an average strain rate of 3.7+/-1.3%/s. The strain rates were chosen to be representative of those observed during upper extremity interaction with frontal and side airbags. The average moment to failure when mass scaled for the 5th centile female was 128+/-19 Nm. Using data from the in situ strain gauges during the drop tests and geometric properties obtained from pretest CT scans, an average dynamic elastic modulus for the female humerus was found to be 24.4+/-3.9 GPa. The injury tolerance for the forearm was determined from 10 female forearms tested at an average strain rate of 3.94+/-2.0%/s. Using 3 matched forearm pairs, it was determined that the forearm is 21% stronger in the supinated position (92+/-5 Nm) versus the pronated position (75+/-7 Nm). Two distinct fracture patterns were seen for the pronated and supinated groups. In the supinated position the average difference in fracture time between the radius and ulna was a negligible 0.4+/-0.3 ms. However, the pronated tests yielded an average difference in fracture time of 3.6+/-1.2 ms, with the ulna breaking before the radius in every test. This trend implies that in the pronated position, the ulna and radius are loaded independently, while in the supinated position the ulna and radius are loaded together as a combined structure. To produce a conservative injury criterion, a total of 7 female forearms were tested in the pronated position, which resulted in the forearm injury criterion of 58+/-12 Nm when scaled for the 5th centile female. It is anticipated that these data will provide injury reference values for the female forearm during driver air bag loading, and the female humerus during side air bag loading.

Output of triglyceride from the sebaceous gland and to the skin surface of cattle.

Radiolabelled fatty acids, when injected intradermally into cattle skin, were largely incorporated into the triglyceride and phospholipid fractions of the sebaceous gland lipids. Linoleic acid was incorporated into the triglycerides to a greater extent than oleic or palmitic acids, whereas the phospholipids had a greater affinity for palmitic acid. The peak uptake of linoleic acid into the glandular triglyceride fraction was at about 61 hours compared with 52 hours and three hours for oleic and palmitic acids. Radioactively 14C labelled triglycerides appeared on the skin surface within one day of intradermal injection of 14C linoleic acid. At an ambient temperature of 20 degrees C, a single output-peak occurred at nine days while at 35 degrees C two peaks at four and eight to nine days were observed. From the data an estimate of 6.5 days for the mean storage time of sebum triglycerides in the hair follicle canal at 20 degrees C has been made.

Incorporation in vitro of 14C fatty acids into bovine sebaceous gland and dermal lipids.

A study has been made of the incorporation in vitro of 14C palmitic, oleic and linoleic acids into the skin lipids of cattle. Linoleic acid was incorporated into the triglyceride (triacylglycerol) fraction of the sebaceous gland lipid at a greater rate than palmitic and oleic acids. Its incorporation was much greater when presented as a free acid than when presented either as cholesteryl linoleate or linoleoyl lecithin. However, the ability of cholesteryl ester and phospholipid to make a substantial indirect contribution of linoleic acid to sebum triglyceride synthesis by hydrolytic release of fatty acid was indicated. The association between the observed preferential incorporation of linoleic acid into the sebum triglycerides and the uniquely unsaturated triglycerides found on the skin surface of cattle is discussed.

Lipid composition of the bovine epidermis.

In contrast to skin surface or sebum lipid, cattle epidermis was found to contain a lower proportion of wax ester and unesterified fatty acid and a high proportion of triglyceride. The epidermal triglycerides differed significantly in their fatty acid composition from those of the skin surface and sebum. In particular they contained extremely low levels of linoleic acid. It is concluded that the skin surface triglycerides and most likely the other major lipid fractions of the bovine skin surface are derived mainly from sebum.