Role of the intermediate filament protein desmin in hypertrophy of smooth muscle was examined in desmin-deficient mice (Des(-/-)). A partial obstruction of the urethra was created, and after 9-19 days bladder weight increased approximately threefold in both Des(-/-) and wild type (Des(+/+)) animals. Bladder growth was associated with the synthesis of actin and myosin. In the hypertrophic Des(+/+) bladder, the relative content of desmin increased. In Des(-/-)mice, desmin was absent. No alterations in the amount of vimentin were observed. Although Des(-/-) obstructed bladders were capable of growth, they had structural changes with a partial disruption of the wall. Des(-/-)bladders had slightly lower passive stress and significantly lower active stress compared with Des(+/+). Des(-/-)preparations had lower shortening velocity. During hypertrophy, these structural and mechanical alterations in the Des(-/-)urinary bladder became more pronounced. In conclusion, desmin in the bladder smooth muscle is not needed for growth but has a role in active force transmission and maintenance of wall structure.

Pilonidal sinus is a well-recognized condition that occurs most commonly in the sacrococcygeal area of younger men. It is hypothesized to be an acquired chronic inflammation condition due mainly to hair trapped beneath the surface. A pilonidal sinus in the sacrococcygeal region is associated with recurrent infection, abscess formation, cellulitis, fistulae, and rarely, squamous cell carcinoma. A pilonidal sinus of the penis is a rare entity. The association of a penile pilonidal cyst and Actinomyces is even more uncommon with only three cases reported previously. Two cases of pilonidal sinus are reported in this paper. One of the cases was associated with actinomycosis. Pilonidal sinus of the penis should be considered in the clinical and pathological differential diagnosis and has to be distinguished from balanoposthitis, epidermal cyst, and carcinoma. The knowledge about possible association with actinomycosis is important to ensure early treatment.

We describe a case of a cutaneous perivascular myoma with features overlapping between the myofibromatosis and the myopericytoma type. The patient is a 58-year-old woman with a painless plaque-like and multinodular lesion in the pretibial dermis and subcutaneous tissue. She had repeated trauma to this site, first in her early youth that left an area of hyperpigmentation, and then again at age 40. The biopsy showed a biphasic pattern with a myofibromatosis-type component composed of spindle cell myoid nodules and more cellular round cell areas. The myopericytoma-like areas appeared to be infiltrating along vessels. These areas contained aggregates of immature-appearing cells arranged concentrically around vascular lumina in a manner reminiscent of pericytes. Immunohistochemical stains showed focal positivity for smooth muscle actin. Immunohistochemical and ultrastructural studies have showed these pericyte-like cells to be of a myoid origin. The reason for the neoplastic proliferation of perivascular myoid cells is presently unknown. The association of trauma and neoplastic transformation of the skin is rare. We report the first case of a cutaneous perivascular myoma arising in a chronic scar.

Attenuated contractile responses to ATP in obstructed rat urinary bladder are due to a lowered rate of calcium influx and maximal peak calcium concentration. This change in Ca2+transients is not due to a decrease in P2X1 receptor density in the smooth muscle cell membranes. Possibly, the increase in cell volume buffers the rapid and transient influx of Ca2+ following purinoceptor activation in the obstructed bladder.

(1): A regional difference exists in pharmacological properties of control detrusor, with a considerable contractile response to stimulation remaining in the supratrigonal muscle after simultaneous cholinergic, adrenergic, and purinergic blockade. (2): The new detrusor was functionally well innervated with no supersensitivity to muscarinic stimulation. (3): The newly formed bladder body had pharmacological properties specific for the supratrigonal segment from which it had developed. (4): There was no regional difference in force-velocity characteristics of the control detrusor. (5): The lowered Vmax in the newly formed bladder might thus be related to growth and regeneration of muscle cells.