Snakes skin shedding

Garter snakes identify their species by tongue flicking at non-volatile, integumentary lipids which they also use in courtship and following conspecific trails. The levels of these lipids fluctuate with hormonal state, skin-shed state, and season (Mason, 1992). 

Excised epidermis Solutes used in excised epidermal studies are also predominantly low-MW polar solutes, as shown in Table 3. However, in a number of studies, the iontophoretic transport of uncharged solutes has also been demonstrated. The phenomenon of electro-osmotic flow will be discussed further in Section II.C. Excised skin used in transdermal studies includes hairless mouse, nude rat, shed snake skin, and human epidermis. The human epidermis is used in one of two forms, dermatomed [28,29] or heat separated [30]. 

Salicylic acid 138 Shed snake skin Elaphe 67... 

Shed snake skin has been proposed as a relatively good model for human skin in transdermal permeation studies [66]. Hirvonen et al. [67] compared the transdermal iontophoresis of sotalol and salicylate in shed snake skin, Elaphe obsoleta, and human cadaver skin. They advised that snake skin should be used with caution as a model for human skin because snake skin has anion-selective properties while human skin has cation-selective properties. 

Itoh, T., Xia, J., Magavi, R., Nishihata, T., and Rytting, J. H. Use of shed snake skin as a model membrane for in vitro percutaneous penetration studies Comparison with human skin. Pharm. Res. 7 1042, 1990. 

NexACT 88 (dodecyl-A,A-dimethylamino isopropionate, DDAIP) is one of a series of dimethylamino alkanoates, reported to be biodegradable, which were developed as potential non-toxic skin permeation enhancers.Much of the early work was carried out using shed snake skin and it was found, using this model, that most of these compounds were equal to or more active than Azone. Studies using human skin... 

Takahashi K, Tamagawa S, Katagi T, Rytting JH, Nishihata T, Mizuno N. Percutaneous permeation of basic compounds through shed snake skin as a model membrane. J Pharm Pharmacol 1993 Oct 45(10) 882-886. 

Skin-snake-model percutaneous absorption Relationships between the in vitro permeability of basic compounds through shed-snake skin as a suitable model membrane for human stratum corneum and their physio-chemical properties were investigated. Compounds with low pKa values were selected to compare the permeabilities of the nonionized forms of the compounds. Steady-state penetration was achieved immediately without a lag time for all compounds. Flux rate and permeability coefficient were calculated from the steady-state penetration data and relationships between these parameters and the physico-chemical properties were investigated. The results showed that permeability may be controlled by the lipophilicity and the molecular size of the compounds. Equations were developed to predict the permeability from the MWs and the partition coefficients of basic compounds. 

Figure 15.4 Permeability coefficients from shed snake skin plotted as a function of log Ko , Elaphe obsoleta-, 0, Python molurus or reticulatus] o, excluded Elaphe obso-leta for invalid K -k, excluded zwitterion Elaphe obsoleta, it, excluded zwitte-rion Python molurus.

Table A4 lists and Figure 15.4 shows 37 permeability coefficient values for 28 compounds (31 fully validated and 6 excluded data points 28 fully validated compounds) measured in shed snake skin. Although the database is small, it is diverse and consists of compounds, predominantly pharmaceutically active compounds, spanning a wide range of molecular structures and properties. These permeability...

Figure 15.7 shows the permeability coefficient regression equations for skin from human (EquationT15.1-l), hairless mouse (EquationT15.1-2), hairless rat (Equation T15.1-3), rat (Equation T15.1-6), and shed snake (Equation T15.1-7) plotted as a function of log for relatively small molecules MW = 100) and larger molecules MW = 300). The regression equations for human, hairless mouse, and shed snake skin are most relevant because these databases are the largest and most diverse. Permeability coefficients in all species increase linearly with log... 

Figure 15.7 Permeability coefficient regressions for human, hairless mouse (HLMouse), hairless rat (HLRat), rat, and shed snake skin plotted as a function of log K at (a) MW = 100 and (b) MW = 300 human (solid), satisfactory correlation (long dashes), limited correlation (short dashes).

Based on the analysis of the small data sets examined hme, the permeability coefficient ratio may not be constant for other species of animals. In particular, there is some evidence that the ratio may depend on MW or for some species. For example, for the shed snake skin data examined here, Ihe pmmeahility coefficient in snake was affected more by MW and log than human skin thus, the permeability coefficient ratio for snake and human skins appears to vary with MW and log K. Based on our present data sets, the ratio of permeabiUty coefficients for hairiess rat and rat skin compared with human skin also may depend on log and MW. However, the data sets for these animal species are so small that this conclusion cannot be supported with confidence. Until more data are compiled to better define these relationships, we recommend using the average ratios of 2.3 for hairless rat skin and 1.9 for rat skin. 

Harada, K., Murakami, T., Kawasaki, E., Higashi, Y., Yamamoto, S., and Yata, N. (1993). In vitro permeability to salicylic acid of human, rodent, and shed snake skin. Journal of Pharmacy and Pharmacology, 45 414-418. 

Rigg, PC. and Barry, B.W. (1990). Shed snake skin and hairless mouse skin as model membranes for human skin during permeation studies. Journal of Investigative Dermatology, 94 235-240. 

When corneous materials are lost from the body surface there remain remnants of intercellular cement. Ultrastructural studies of squamate skin-shedding (see refs, in Maderson, 1985), clearly reveal the association of these materials with the Oberhautchen (Smith et al., 1984). While such could be semiochemicals, their efficacy would diminish rapidly due to abrasion during environmental contact. However, between closely overlapping scales e.g., in snakes, one could predict a longer functional half-life. 

Because we used methylene chloride as a solvent to extract pheromone-containing substances from shed snake skins, we hypothesized that resulting extracts were lipoidal in nature. And because our behavioral bioassays indicated that neonatal rattlesnakes responded differentially to extracts from conspecific and heterospecific sources, we hypothesized that there might be detectable differences between the chemical structures of such extracts. Additionally, knowledge of the extract s chemical structure might provide insight into their biological roles. 

Snakes seem to inspire either awe or fear. They hiss, they slither, they rattle, they don t hlink, they shed their skin and do dozens of other things that are disturhing to see. A few species can puff themselves up and others can play dead. Some have horns or odd protrusions and worst of all, their venom can cause severe pain or death within minutes when sprayed or injected through their needle-sharp fangs. For many of us, this one attrihute alone is the stuff of nightmares. 

Rattlers get a new rattle segment each time the snake sheds its skin which is normally about 3 to 4 times per year. Hatchling rattlesnakes are born with only one segment on their rattle called a button. This brand new rattle is noiseless until the hatchling rattler sheds its skin for the first time and adds a segment to the button. The rattle makes noise when segments click against each other. 

Figure 15.1 through Figure 15.6 show skin permeability coefficient measurements from hairless mouse, hairless rat, rat, shed snake, and the lesser-studied animals (guinea pig, marmoset, rabbit, pig, dog, mouse, nude rat) plotted as a function of log In Figure 15.1 to Figure 15.4 and Figure 15.6, compounds that were more than 90% ionized are identified by the form of the dominant ionic species (that is, cation, anion, or zwitterion) and labeled as excluded. Ionized species with undetermined log are plotted to the left of the dashed vertical line located at log = -6.0. Cations are plotted at log = -6.5, anions at log = -7.0, and zwitterions at log = -7.5. A few permeability coefficient measurements that are... 

Devine (1977b) had previously found that esterified cholesterol partitioned from his trichloroethylene or chloroform methanol extracts of shed skins was responsible for trail-following in garter snakes, and we were curious whether our results were due to a specific lipid or if it was a quantitative phenomenon only. We found that the sera of estrogen-treated females contained much more lipid than the sera of males, and that estrogen treatment of males resulted in significantly elevated... 

Figures 1 and 2 show sections of epidermis from the nuchal region (dorsal, along the back of the neck) of one snake, a pregnant C. v. viridis. Figures 1 and 2 are sections of biopsied skin, 10 days post-shed.

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