Morphogenesis of the ureterovesical junction:a histologic and microanatomic study in the rat.

OBJECTIVES: To investigate the development of the ureterovesical junction in rats. METHODS: A total of 110 albino rats (50 prenatal and 60 newborn) with a gestation of 21 days were studied at the age of 17 days after conception until 5 days after birth. The lower urinary tract was microdissected. Microphotography (110 animals), histologic examination (44 animals), and scanning electron microscopy (66 animals) of the ureterovesical junction were performed. Urea and creatinine from the amniotic fluid of 20 fetuses and from the urine of 10 neonates were measured. RESULTS: At day 17 after conception, separate penetration of the mesonephric duct and ureter into the wall of the urogenital sinus was observed. Continuity between the lumen of the ureter and the urogenital sinus was established on day 19 after conception. The straight passage of the intramural ureter into the urogenital sinus at day 17 after conception changed to the definitive L-shape with a vertical entry into the bladder on day 5 after birth. In the distal ureter, the change of the mesenchymal tissue into immature smooth muscle was first observed at birth, and the muscle became mature on the fifth postnatal day. At birth, Waldeyer's sheath was recognized. The creatinine and urea levels were stable prenatally (average 22.4 micromol/L and 6.88 mmol/L, respectively) and rose significantly postnatally (average 133 micromol/L and 32.65 mmol/L, respectively). CONCLUSIONS: The attachment of the ureter to the urogenital sinus and later to the bladder, the modification of its passage, and its mobility within Waldeyer's sheath may be essential in preventing vesicoureteral reflux. The production of urine and its flow does not seem to be the trigger of ureteral smooth muscle formation.

In situ evaluation of single-cell lysis by cytosol extraction observation through fluorescence decay and dielectrophoretic trapping time

We present a new method for lysis of single cells in continuous flow, where cells are sequentially trapped, lysed and released in an automatic process. Using optimized frequencies, dielectrophoretic trapping allows exposing cells in a reproducible way to high electrical fields for long durations, thereby giving good control on the lysis parameters. In situ evaluation of cytosol extraction on single cells has been studied for Chinese hamster ovary (CHO) cells through out-diffusion of fluorescent molecules for different voltage amplitudes. A diffusion model is proposed to correlate this out-diffusion to the total area of the created pores, which is dependent on the potential drop across the cell membrane and enables evaluation of the total pore area in the membrane. The dielectrophoretic trapping is no longer effective after lysis because of the reduced conductivity inside the cells, leading to cell release. The trapping time is linked to the time required for cytosol extraction and can thus provide additional validation of the effective cytosol extraction for non-fluorescent cells. Furthermore, the application of one single voltage for both trapping and lysis provides a fully automatic process including cell trapping, lysis, and release, allowing operating the device in continuous flow without human intervention.

Characterization of volatile organic gunshot residues in fired handgun cartridges by headspace sorptive extraction

In forensic investigation of firearm-related cases, determination of the residual amount of volatile compounds remaining inside a cartridge could be useful in estimating the time since its discharge. Published approaches are based on following the decrease of selected target compounds as a function of time by using solid phase micro-extraction (SPME). Naphthalene, as well as an unidentified decomposition product of nitrocellulose (referred to as "TEA2"), are usually employed for this purpose. However, reliability can be brought into question given their high volatility and the low reproducibility of their extracted quantities. In order to identify alternatives and therefore develop improved dating methods, an extensive study on the composition and variability of volatile residues in nine different types of cartridges was carried out. Analysis was performed using headspace sorptive extraction (HSSE), which is a more exhaustive technique compared to SPME. 166 compounds were identified (several of which for the first time), and it was observed that the final compositional characteristics of each residue were strongly dependent on its source. Variability of single identified compounds within and between different types of cartridge, as well as their evolution over time, was also studied. Many explosion products containing up to 4 aromatic rings were found to be globally present in high proportions amongst residues. 27 of them (excluding naphthalene) also presented detectable decreases during the first 24 h. Therefore, they could be used as complementary target analytes in future dating methods.