Dorsal dermis

To emphasize this, Behl et al. reported that only in the absence of the SC were differences in the penetration of hydrocortisone observed between the abdomen and the dorsal sites of rats. This was believed to be due to the thicker dorsal dermis as compared with that of the abdomen. 

Next, a 1 year subcutaneous implantation study in mice was performed (22). Small pieces of poly(N-palmitoylhydroxyproline ester) (approximately 10 mg per implant) were implanted subcutaneously in the dorsal area of the animals. The implants were placed between the dermis and the adipose tissue layer. Groups of mice were sacrificed 4, 7, 14, 16, and 56 weeks postimplantation. 

For the experiment, the dorsal skin of young rats (Wistar or a comparable strain) is shaved and washed with an antibiotic solution (containing, e.g., streptomycin, penicillin, chloramphenicol, and amphotericin in concentrations inhibiting bacterial growth). After skin excision, excess fat is peeled off and the skin is placed over the end of a polytetrafluoroethylene tube with the epidermal side in touch with the hollow cylinder. The skin is fixed with an O-ring and the tube interior is sealed. The side of the dermis is then submersed in a magnesium sulphate solution (154 mM). The samples are applied at 30°C to the epidermal side of the skin in such a way that the skin interface is fully covered. After the incubation time, the substances are removed with prewarmed water the skin surface tension is decreased with ethanol which is subsequently replaced with magnesium sulphate solution (154 mM). 

Intradermal injections. It is commonly believed that due to the extremely thin dermis and epidermis of the mouse truncal skin, injections into the dermis are the same as subcutaneous. However, it is possible to stretch the dorsal or ventral skin and, using a very small gauge needle, position it within the layers of the skin instead of through the skin to produce small blisters with the injected material. 

In general, the basic architecture of the integument is similar in all mammals. However, differences exist in the thickness of the epidermis and dermis, the number of cell layers, and the blood flow patterns between species. Additionally, differences exist within the same species at different body sites. Skin is thickest over the dorsal and lateral surfaces and thinnest on the ventral and medial surfaces of the body. The stratum corneum is thickest in glabrous skin regions such as the palmar and... 

There are variations in the thickness of the epidermis and dermis within species in different regions of the body (Table 35.1). Skin is the thickest over the dorsal and lateral surfaces of limbs, and thinner on the ventral and medial surfaces of limbs. The back (thoracolumbar lumbar junction) is usually thicker than the abdomen. In areas possessing high hair density, the epidermis is thin whereas in glabrous areas such as mucocutaneous junctions, the epidermis is thicker. The palmar and plantar surfaces consist of extremely thick stratum corneum because it is an area where abrasive action occurs. 

Figure 2. (A) Dorsal skin of unexposed channel catfish [Ictalurus punctatus). Epidermis and dermis close to the dorsal-most portion is 10 or more cells thick and contains some mucous (single arrow) and club (double arrow) cells. Scale bar equals 20 pm. (B) Dorsal-lateral skin of channel catfish exposed to UV-B radiation for 24 h. Club cells are often vacuolated and hypertrophied (double arrow) in this group. Sunburn cells (single arrow) with perinuclear halo are also observed. Scale bar equals 10 pm. [From Ewing et al. 17.]...

Skin. The potential to cause skin irritation was investigated in rats, guinea pigs and mice who had 0.1 ml 12.5% CS in either com oil or acetone applied unoccluded to the shaven dorsal trunk skin for 6 h, and the area subsequently and periodically inspected up to 21 days for local reactions. Erythema was more marked than oedema, and both resolved by 7 days post-application. Histological examination of skin biopsies taken from a few animals at 3 days after CS application showed foci of epidermal necrosis in the contaminated area with spongiosis and acute inflammatory infiltration of the outer dermis (Ballantyne and Swanston, 1978). 

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