The maturation of cortical keratin in filiform hairs of the rat penis

Formation, structure, and function of extra-skeletal bones in mammals

This review describes the formation, structure, and function of bony compartments in antlers, horns, ossicones, osteoderm and the os penis/os clitoris (collectively referred to herein as AHOOO structures) in extant mammals. AHOOOs are extra-skeletal bones that originate from subcutaneous (dermal) tissues in a wide variety of mammals, and this review elaborates on the co-development of the bone and skin in these structures. During foetal stages, primordial cells for the bony compartments arise in subcutaneous tissues. The epithelial-mesenchymal transition is assumed to play a key role in the differentiation of bone, cartilage, skin and other tissues in AHOOO structures. AHOOO ossification takes place after skeletal bone formation, and may depend on sexual maturity. Skin keratinization occurs in tandem with ossification and may be under the control of androgens. Both endochondral and intramembranous ossification participate in bony compartment formation. There is variation in gradients of density in different AHOOO structures. These gradients, which vary according to function and species, primarily reduce mechanical stress. Anchorage of AHOOOs to their surrounding tissues fortifies these structures and is accomplished by bone-bone fusion and Sharpey fibres. The presence of the integument is essential for the protection and function of the bony compartments. Three major functions can be attributed to AHOOOs: mechanical, visual, and thermoregulatory. This review provides the first extensive comparative description of the skeletal and integumentary systems of AHOOOs in a variety of mammals.

Advantages and Limitations of Salmon-Gal/Tetrazolium Salt Histochemistry for the Detection of LacZ Reporter Gene Activity in Murine Epithelial Tissue

The Escherichia coli LacZ gene is a widely used reporter for gene regulation studies in transgenic mice. It encodes bacterial β-galactosidase (Bact β-Gal), which causes insoluble precipitates when exposed to chromogenic homologues of galactose. We and others have recently reported that Bact β-Gal detection with Salmon-Gal (S-Gal) in combination with nitro blue tetrazolium chloride (NBT) is very sensitive and not prone to interference by acidic endogenous β-galactosidases. Unfortunately, as we show here, the method appears to be inadequate for evaluation of Bact β-Gal expression in keratinized epithelial appendages but not in other keratinized epithelia. NBT in the reaction mixture, just as other tetrazolium salts, inevitably causes unwanted staining artifacts in lingual filiform papillae, penile spines, and hair fibers by interacting with keratin sulfhydryl-rich regions. The methodological limitation can be overcome in part by pretreating the tissues before the S-Gal/NBT staining with an iodine-potassium iodide solution. Alternatively, the use of iodonitrotetrazolium chloride instead of NBT in the S-Gal reaction mixture provides enough color resolution to distinguish the specific Bact β-Gal staining in orange from the artifact staining in dark red. In summary, we provide evidence that S-Gal/NBT histochemistry has limitations, when staining keratinized epithelial appendages.

Morphology of the erect glans penis in rats under various gonadal hormone conditions

The scanning electron microscope (SEM) was used to compare erect and nonerect penile glandes of gonadally intact Norway rats (group I) and of castrated rats exposed to the following hormonal conditions: maintained with testosterone (T)-filled Silastic capsules implanted subcutaneously (group T); maintained with implants of estradiol (E) for 8 or 12 days (group E1); maintained with E implants for 10 weeks (group E10); maintained with E implants for 9 weeks, then injected daily with testosterone propionate for 8 or 17 days (group E/T). As in previous SEM depictions of nonerect glandes of intact rats, spines projected toward the base of the glans at a shallow angle from the sulci of deep epithelial folds. In contrast, the folds on erect glandes of groups I and T were completely smoothed, and the spines were themselves erected. The penile cup formed at the distal end of the erect glans also contained spines; these were centrifugally directed at the rim and centripetally directed on the inner surface of the cup. The glandes of group E1 males were similar to those in groups I and T, with the spines showing no disorientation. Males in group E10 lacked spines in the cup and along most of the shaft of the glans, but erection revealed many sharp spines just proximal to the cup and on its rim. In group E/T, no papillae were detectable on the nonerect glandes, but erection revealed many small rounded papillae on the shaft and within the cup. The erection of the spines that occurs on the shaft and in the cup of the erect glans may facilitate previously proposed functions of the spines, including vaginal and cervical stimulation and removal of the copulatory plug. Our perfusion method may also facilitate estimation of the number, size, distribution, and hormonal sensitivity of penile papillae.