Eighteen Landrace pigs and 12 Göttingen mini-pigs were evaluated in a study of experimental bladder outflow obstruction. Twenty-two of the animals underwent partial bladder outflow obstruction for periods up to 12 months. The subsequent changes were assessed using cystometric, physiological and morphological means. There was a consistent increase in the voiding pressures and a concomitant reduction in the flow rates in all the obstructed animals. Seventy-seven per cent of the obstructed animals showed cystometric evidence of bladder instability. In vitro studies showed an increase in sensitivity to exogenously applied agonists and a reduction in sensitivity to intramural nerve stimulation. Morphological studies showed an inverse correlation between neuronal density and the duration of obstruction. These changes are typical of post-junctional supersensitivity secondary to partial denervation. These results suggest that agents capable of stabilising the bladder smooth muscle membrane may be useful in the treatment of detrusor instability secondary to bladder outflow obstruction.

Summary. Histological and histochemical analysis of biopsy samples of pubococcygeus muscle obtained from asymptomatic women and from women with stress incontinence of urine, with or without genitourinary prolapse, have been coinpared. In the asymptomatic women both age and parity appeared to be related to the morphological features of the samples and in particular those obtained from the posterior part of the pubococcygeus. In the symptomatic women there was a significant increase in the number of muscle fibres showing pathological damage which were obtained from the posterior part of the pelvic floor. The ränge of diameters of both Type I and Type II fibres obtained from this region was significantly different between symptomatic and asymptomatic women. These findings may be attributable to partial denervation of the pelvic floor in patients with urinary stress incontinence with or without genital tract prolapse.

In a group of patients in whom bladder outflow obstruction had been confirmed urodynamically, quantitative assessment of the amount of autonomic nerve in detrusor biopsy samples has been carried out using light and electron microscope techniques. In each specimen allowance was made for muscle cell hypertrophy and increases in connective tissue, both of which occurred in response to bladder outflow obstruction. Similar quantitative assessment was performed on bladder biopsy samples from a group of unobstructed 'control' patients. When the results from the two groups were compared a statistically significant reduction in the amount of autonomic nerve supplying detrusor muscle was demonstrated in the obstructed group. This finding provides additional evidence that functional impairment of the urinary bladder occurs in response to outflow obstruction and emphasizes the need for prompt relief of the condition.

1. Genetic selection of broilers may have pushed muscle fibres to their maximum functional size constraints. Broiler (B), female great-grandparent (GGP) and layer (L) lines were weighed, blood sampled and killed from 5 to 25 weeks of age. 2. At 25 weeks, Pectoralis major (Pm) fibre size reached by the B (65.9 microm) and GGP (59.8 microm) were 1.5 times greater than the L (38.1 microm). In the B and GGP lines, fibre growth of the Pm markedly exceeded that of the Biceps femoris (Bf) muscle. However, in the L line, fibre growth of the Pm and Bf muscle was comparable. Connective tissue content was generally higher in the Bf than in the Pm of all lines. 3. Centralised nuclei were observed predominantly in Pm, and may regulate fibre size. Both large muscle fibres and inadequate capillary supply may induce metabolic stress in B and GGP lines due to the large diffusion distances for oxygen, metabolites and waste products. 4. Enzyme markers of muscle damage (creatine kinase (CK), lactate dehydrogenase (LDH) and aspartate aminotransaminase (AST)) and histopathological analysis of Pm and Bf indicated greater myopathy in B and GGP vs L. 5. Regenerative processes were associated with oestrogen secretion. Reduced CK and LDH preceded egg yolk precursor production and increased calcium uptake for eggshell synthesis in all three lines. Oestrogen may stimulate muscle fibre regeneration and recovery as a myo-protective adaptation to potentially detrimental changes in calcium economy during egg production.

As part of an ongoing study on trabeculation of the human urinary bladder, morphological and morphometric techniques have been employed on biopsy samples of detrusor muscle removed from control and urodynamically obstructed patients. In control material the mean profile area, profile diameter and nucleated profile percentage of bladder smooth muscle cells were determined. The values of the same parameters were obtained for smooth muscle cells in samples from urodynamically obstructed and endoscopically trabeculated patients. Comparison of the results obtained from the two groups showed that smooth muscle cells undergo compensatory hypertrophy in response to outflow obstruction. Furthermore, connective tissue infiltration of detrusor muscle bundles is a characteristic of those bladders which possess cells showing the largest increase in cell size.