Tissue layers

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 overweight adolescents and adults, autoinjectors containing a 0.5-mg dose of epinephrine are needed however, this dose is not available in most countries. Moreover, in many overweight people, attempts to inject epinephrine intramuscularly from most currently available autoinjectors are likely doomed to failure, because the attached needle is too short to penetrate the poorly vascularized adipose tissue layer over the vastus lateralis [26]. 

Four major tissue layers, from the lumen outward, form the large intestine the mucosa, submucosa, muscularis externa, and serosa (Fig. 88-2). Complete replacement of surface epithelial cells occurs approximately weekly, with the total number of epithelial cells remaining constant in normal colonic tissue. As patients age, abnormal cells accumulate on the surface epithelium and protrude into the stream of fecal matter their contact with fecal mutagens can lead to further cell mutations and eventual adenoma formation.4... 

Seborrhea in which thickened, hard, rigid, and pigmented patches occur with thickening of the dermal connective tissue layer A disease of the sebaceous glands marked by excessive discharge... 

Ion flux, the movement of ions across a biological membrane, cell, or tissue layer. This flux may be into the cell or organism (influx) or out of the cell or organism (efflux). 

The oral mucosa is anatomically divided into three tissue layers (Fig. 1) [10] the epithelium, the basement membrane, and the connective tissues. 

A concerted effort is needed to increase our understanding of the transfer and uptake of reactive gases in the lung. A program in this field should involve in vitro model studies, animal experiments, and clinical studies. More information is required on the chemical, physical, and morphologic properties of the mucous layer and the kinetics of the reactions of ozone in the mucous and tissue layers. Experimental data on uptake and dosage for ozone and other oxidants are difficult to obtain for the tracheobronchial and pulmonary regions. Such data for animals and humans will be needed to test the present simple transport models, before further refinements are made. 

To model sulfur dioxide absorption by the blood through the walls of the upper airways, as demonstrated by Frank et one must include the transport rates of sulfur dioxide across a mucus-tissue interface, a tissue layer, and a tissue-blood interface (Figure 7-2). For the case of release of dissolved gas back into the exhaled air, which is depleted of gas in the lower lung, the mucus layer would still represent the greatest resistance to transfer. Consequently, the overall transfer coefficient, kg, would still be given by ki/H. 

The processes of convection, axial diffusion, radial diffusion, and chemical reaction in the liquid and tissue layers all occur simultaneously. A rigorous approach requires solution of several simultaneous differential equations. To avoid this complexity in preliminary models, the transfer... 

The development of models requires more knowledge about the chemical, physical, morphologic, and flow properties of the mucus layer the kinetics of the reactions of ozone in the mucus and tissue layers and the molecular diffusivity of ozone in these layers. Similar information is needed for the hydroperozy and singlet oxygen, O, (a A), free radicals, which are reactive interme ates in photochemical smog. 

In the area of a gastric or duodenal peptic ulcer, the mucosa has been attacked by digestive juices to such an extent as to expose the subjacent connective tissue layer (submucosa). This self-digestion occurs when the equilibrium between the corrosive hydrochloric acid and acid-neutralizing mucus, which forms a protective cover on the mucosal surface, is shifted in favor of hydrochloric acid. Mucosal damage can be promoted by Helicobacter pylori bacteria that colonize the gastric mucus. 

The blood vessels of the fetus and mother are separated by a number of tissue layers that collectively constitute the placental barrier. Drugs that traverse this barrier will reach the fetal circulation. The placental barrier, like the blood-brain barrier, does not prevent transport... 

The major limitation to developing therapeutic proteins in nonparenteral dosage forms is the poor permeability of these water-soluble and hygroscopic macromolecules across the tissue layers at the site of drug administration. These tissue layers include the epithelium of the gastrointestinal tract, the stratum corneum of the skin, and the epithelium lining of the alveoli and nasal cavity. 

Peristome teeth solid, rarely absent, developed from two or more tissue layers of the sporangium, not transversely barred or... 

The others form an extra-embryonic suspensor (Fig. 32-8B).475 The apical part of the embryo develops the shoot meristem and the central part the radial pattern of tissue layers characteristic of plants. The root meristem develops from the basal portion of the embryo. Movements of proteins that provide positional cues are involved in the development of the embryo.476,477 Early embryonic and endosperm development is largely under maternal control. Most paternal genes may be initially silent.478... 

Microneedles, so termed as they commonly range from 100 to 1000 pm in length, are designed to perforate the stratum corneum thus providing a direct and controlled route of access to the underlying tissue layers. When inserted into the skin, microneedles create microscopic punctures through the stratum corneum and into the viable epidermis. The length of the microneedle is controlled to ensure that the depth of penetration does not... 

Fig. 1 Basic structure (left side) and the absorption spectra (right side) of some photosensitizers. The absorption spectra of porphyrins (derived from porphins) consists of a Soret band (around 400 nm) and four Q-bands. Upon reduction of one or two double-bonds of the tetra-pyrrole structure or by expanding the number of 7i-electrons (by expanding the ring structure), the outermost Q-band becomes bathochromically shifted and the absorption coefficient increased as indicated on the figure. As described in the text, such chemical modifications are important for improving the therapeutic effect in deeper tissue layers...

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