Recent observations on the ultrastructure of human urothelium

Abstract

An electron microscopic study of normal bladder urothelium of elderly patients ranging in age from 61 to 82 years has shown the occurrence of unusually thin regions consisting of either one or two layers of undifferentiated cells interspersed between 3--4 cell layers thick regions. A morphometric study has confirmed the existence of a pattern of cytodifferentiation in cells of the thick region. The generally microvillous nature of the luminal surface is attributed to incompletely differentiated cells that have come to occupy the superficial layer. The lack of thickened and/or asymmetric membrane plaques in luminal plasma as well as the dearth of characteristic precursor vesicles in the cytoplasm are also explicable in terms of a failure of normal cell differentiation. It is suggested that the unusual features noted are consequences of tissue ageing rather than prognostic of cancer. There are indications that the aged urothelium may be prone to increased leakiness and the bladder tissues may therefore be at greater risk from urine-borne chemicals and carcinogens.

Correlation between numbers of desmosomes and the aggressiveness of transitional cell carcinoma in human urinary bladder

“…The fine structure of normal adult human urinary bladder epithelium has been described in detail elsewhere.7.iS. 17,2324 Briefly , the luminal membrane of superficial cells appeared as a symmetric unit membrane which was approximately 10 nm thick4*17.23 and was coated with a glyc~calyx. '~ Asymmetric unit membrane plaques, which are prominent in non-primates but not adult humans,'fi were infrequently encountered in adults in the age group (e.g.. fifth to seventh decade) in which urinary bladder carcinoma is most preval-ent.2,4.…”

The effect of aging on cholinergic receptor binding in the rat urinary bladder

“…Elderly patients are at increased risk for voiding dysfunction. While many of these problems are secondary to other diseases, there are those who have no apparent predisposing factor for their voiding difficulties [Brocklehurst, 19731. To examine this issue, the effect of aging on the urinary bladder has been studied at the light microscopic and ultrastructural levels [Monney and Hinman, 1974;Jacob et al, 1978;Phillips and Davies, 19801. However, these investigations have failed to provide any insight into the possible cause of voiding dysfunction in the otherwise normal aged patient.…”

Occurrence of enzymes of free radical metabolism suggests the possible cytotoxic capacity of the transitional epithelium of the human ureter

“…Our light-microscopic study does not allow a lysosomal or cytosolic location of the reaction precipitate to be discriminated. Previous electronmicroscopic studies have shown that lysosomes are tightly packed in this supranuclear cytoplasm and that only small cytoplasmic areas between them are free of these organelles (Jacob et al 1978;Holstein et al 1994). Thus, the SOD-reaction product may be distributed within the free cytoplasmic areas between the large lysosomes of the supranuclear region of the superficial cells; this location might contribute to the granular appearance of the reaction product.…”

“…The results of the present study show that TRAP is localized within the apical cytoplasm of the superficial cells. In contrast, light-and electronmicroscopic enzyme histochemical studies have revealed that the enzyme activity of the tartrate-sensitive acid phosphatase (isoenzyme ACP2 or conventional lysosomal acid phosphatase) is located within large lysosomes or lysosomal complexes of the supranuclear cytoplasm of the superficial cells (Hicks 1966;Jacob et al 1978;Holstein et al 1994). Since the TRAP activity of other cells is also found in lysosomes (Drexler and Gignac 1994), it seems likely that the product of the immunocytochemical staining in the urothelial superficial cells is located within the acid-phosphatase-positive small lyso- somes and endocytotic vesicles of the subplasmalemmal cytoplasm, as shown by Holstein et al (1994).…”

“…Strong acid phosphatase activity has been detected by light and electron microscopy in lysosomes of urothelial cells, especially of the superficial layer. The exact type of acid phosphatase isoenzyme has not however been determined (Hicks 1966;Jacob et al 1978;Holstein et al 1994). These findings have stimulated us to investigate further which of the well-characterized isoenzymes of acid phosphatase (Li et al 1970) are expressed by the urothelial cells, because one of these isoenzymes, termed tartrate-resistant acid phosphatase (TRAP; also known as isoenzyme 5, ACP5, or purple acid phosphatase), is able to generate hydroxyl radicals or superoxide anion equivalents because of its binuclear mixed-valent iron center, by Fenton chemistry (Sibille et al 1987;Suerbaum et al 1993;Hayman and Cox 1994).…”