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N Smeulders

Publications and source records attributed to N Smeulders.

7 recordsLinked to original sources
PubMed2003

Extracellular matrix protein expression during mouse detrusor development.

BACKGROUND/PURPOSE: Extracellular matrix proteins are implicated in regulating cell proliferation and differentiation. The authors systematically analysed the expression of elastin; collagen types I, III, IV; laminin; and fibronectin during mouse detrusor muscle development, a period during which downregulation of detrusor proliferation and increasing smooth muscle differentiation is known to occur. METHODS: Embryonic days 14 (E14) and 18 (E18), and postnatal day 1 (D1) and week 6 (6wk) were examined, a period spanning the inception of the bladder to postnatal maturity. Immunohistochemistry of whole bladders was used to immunolocalise protein expression, and Western blot of dissected detrusor layers was used to semiquantify soluble protein expression. RESULTS: All proteins were detected at all 4 stages. Statistically significant increases were documented for elastin (E14 to 6wk), collagen type I (E18 to 6wk), collagen type III (D1 to 6wk) and laminin (E14 to 6wk). Fibronectin levels were relatively high up to D1, after which levels declined significantly. Collagen type IV levels decreased significantly (E18 to 6wk). CONCLUSIONS: The authors postulate that changing levels of laminin and fibronectin have opposing effects on the transition from proliferating primitive mesenchymal cells to differentiated detrusor muscle. Furthermore, changes in collagen type III and elastin may be important for bladder compliance.

Animals↗
PubMed2003

Cell biology of bladder development and the role of the extracellular matrix.

The bladder is unique. It is the most distensible organ in the body. If the normal pattern of development is disturbed, the bladder can become dysfunctional and poorly compliant. Renal outcome is intimately linked to bladder function and hence bladder development. In this review we describe our current knowledge of the molecular processes that govern bladder development, with particular emphasis on the role of the extracellular matrix. Finally, we suggest a hypothetical model for bladder development.

Animals↗
PubMed2002

Smooth muscle differentiation and cell turnover in mouse detrusor development.

PURPOSE: We systematically analyzed detrusor muscle differentiation in normal mice with a focus on cell turnover (proliferation and apoptosis) as well as on expression of the muscle specific proteins alpha-smooth muscle actin and desmin. MATERIALS AND METHODS: The stages examined were embryonic days 14 and 18, and postnatal day 1 and week 6, representing a period spanning organ inception to postnatal maturity. Alpha-smooth muscle actin, desmin and proliferating cell nuclear antigen were assessed by immunohistochemical testing of whole bladders and Western blot analysis of dissected detrusor layers. Apoptosis was detected in tissue sections by end-labeling. RESULTS: Alpha-smooth muscle actin was expressed by the detrusor layer throughout maturation with levels significantly increasing from embryonic days 14 to 18 and cytoplasmic staining gaining in uniformity postnatally. Desmin expression in the detrusor was insignificant at embryonic day 14 but increased progressively thereafter. Proliferating cell nuclear antigen expression in the detrusor was highest at organ inception and fell stepwise at each developmental stage with low levels postnatally. Apoptosis in the detrusor was only detected at embryonic day 14. CONCLUSIONS: These results demonstrate that morphological growth of the mouse detrusor muscle is accompanied by complex serial changes in the expression of muscle specific proteins and in cell turnover. Strikingly, detrusor muscle cell differentiation and proliferation are inversely related. These detailed studies may serve as a comparison for future experiments involving aberrant mouse bladder development.

Actins↗
PubMed2001

Neoplasia in adult exstrophy patients.

OBJECTIVE: To document the incidence of neoplasia in a cohort of 103 patients born with classical exstrophy. PATIENTS AND METHODS: The notes of patients born before 1964 with exstrophy were reviewed retrospectively. The patients were divided into two groups; 42 were thought to be at high risk of developing neoplasia because they had (at some time) had mixing of urine and faeces in a colorectal reservoir, whereas 61 had never been exposed to such a mixture and were thought to have a low risk of neoplasia. RESULTS: At a minimum of 35 years of follow-up, complete data were available for 61 patients; 42 were lost to follow-up, of whom 14 were at high risk and 28 at low risk of neoplasia. In the high-risk group, there were three with colonic carcinoma (two of whom presented before 1980 and died), one with carcinoma in situ of the colon, 10 with benign colonic neoplasms and three with bladder cancer (two of whom died). In the low-risk group, there was one patient with bladder cancer (who died) and one with a clear cell carcinoma of the kidney. Three of the four patients with bladder cancer had undergone cystectomy before 5 years of age. Assuming that all the lost patients are alive and free of neoplasia, the risk of neoplasia in adults born with exstrophy is 17.5%. The main risk is in those who have been exposed to mixing of urine and faeces in a colorectal reservoir (38%). Even in low-risk patients the risk of malignant neoplasia is 3.3% at a median (range) age of 42 (40-44) years, which is 27 times higher than that of the age-matched general population. CONCLUSIONS: Annual colonoscopy of patients deemed at high risk of colorectal neoplasia appears to be an effective screen for colorectal carcinoma, by identifying a premalignant stage, as there were no deaths after this was introduced. Despite bladder closure or diversion surgery within the first few years of life, patients with exstrophy have an almost 700-fold greater incidence of carcinoma of the bladder than the age-matched general population. Early cystectomy is not protective.

Adult↗
PubMed1999

Lateral ligaments of the rectum: an anatomical study.

BACKGROUND: The lateral ligaments of the rectum are surrounded by confusion and misconception. Their identification before 'hooking them on the finger', clamping and ligating is considered in many surgical texts to be an essential step in mobilization of the rectum. By contrast, it is the experience of many colorectal surgeons that the mesorectum can be dissected out either by diathermy or sharp dissection alone. METHODS: Dissection in the mesorectal plane was performed on 28 cadaveric pelves. RESULTS: In ten of the pelves, no connective tissue structure crossed from the pelvic side wall to the rectum. The remaining 18 had only very insubstantial connective tissue strands crossing this space. A total of 17 middle rectal arteries were found, all of them unilateral. Fourteen of these vessels crossed the mesorectum independent of any structure, while the remainder were part of a neurovascular bundle with a connective tissue element. CONCLUSION: It is proposed that the 'lateral ligaments' of the rectum do not exist and that the term should be dropped from surgical texts. When present, the middle rectal artery is a small vessel, close to the pelvic floor. The entire rectum may be mobilized by sharp dissection without the need for clamping or ligation of any significant structure.

Aged↗
PubMed1994

The role of delineation and spatial frequency in the perception of the colours of the spectrum.

The observations of the spectrum made by Newton, Young, Wollaston and Helmholtz are approximated and accounted for. Increasing the number of delineations allows progressively more bands differing in colour to be perceived, in addition to the three blocks of colour seen in the undelineated spectrum. The rate at which further delineation permits more colours to be observed decreases, however, so that up to 30 colours can be perceived in the subdivided spectrum. The wavelength discrimination measurements agree well with previous data. Enhanced colour discrimination is shown to require luminance contrast transients containing only the first few Fourier harmonics.

Adult↗