Analysis of the influence of coupled diffusion on transport in protein crystal growth for different gravity levels

Diffusion has a central role in protein crystal growth both in microgravity conditions and on ground. Recently several reports have been focused on the importance to use the generalized Fick's equations in n-component systems where crystals grow. In these equations the total flux of each component is produced by the own concentration gradient (main flow) and by the concentration gradient of the other components (cross-flow) present in the system. However in literature the latter effect is often neglected, and the so-called pseudo-binary approximation is used. Lin et al. (1995) proposed a mathematical model to evaluate the concentration profile of the species present around a growing protein crystal. Although the model is reliable, it suffers of the pseudo-binary approximation (neglecting cross term diffusion coefficients and using binary diffusion coefficients), probably because of the lack of multicomponent diffusion data. The present model is based on the experimental set-up proposed by Lin et al. (1995). Nevertheless we have included the coupled diffusion effects, according to the correct description of the matter transport through the generalized Fick's equations. The crystal growth rate is calculated for different gravity levels. The model has been applied to the ternary lysozyme-NaCl-water and quaternary lysozyme-poly(ethylene glycol) (PEG)-NaCl-water systems using recent diffusion data.

[Diagnostic approach to newborns with prenatal diagnosis of hydronephrosis]

Prenatal ultrasound examination has radically changed physician's attitude toward hydronephrosis. Fetal hydronephrosis must be searched out and looked at with a wider vision than it was done in the past. A mechanical obstruction must be suspected indeed, but often we have to face a functional dilatation, caused by immaturity, which can clear up in uterus or which will simply require a careful follow-up during the post natal period. Vesicoureteral reflux may count for 10 to 33% of urinary tract dilatations. There are no pathological limit values clearly stated in literature: a pyelectasis can only be the expression of a normal anatomical variability, without features of disease. In creating a diagnostic protocol for the newborn with prenatal diagnosis of hydronephrosis, all these possibilities must be accounted for the risk of focusing on mechanical obstruction is to overestimate and over-treat children that will never obtain any benefit from a surgical procedure.

Transport Properties for Aqueous Solution of Sodium Sulfonate Surfactants

Isothermal mutual diffusion coefficients (D) have been measured for binary aqueous solutions of sodium alkylsulfonates at 25 degrees C. The diffusion coefficient values drop as the concentration of micelles in the system increases. As the length of the hydrocarbon chain increases, the observed drop in D becomes increasingly sharp and shifts to lower concentrations. When the micellization process is treated as a chemical equilibrium, diffusion coefficients lead to the calculation of the thermodynamic parameters association number, n, and the equilibrium constant, K. These parameters are briefly discussed in connection with the alkyl chain length of the surfactants. Copyright 1999 Academic Press.

Transport Properties for Aqueous Sodium Sulfonate Surfactants

Intradiffusion coefficients of sodium alkylsulfonates [CH3-(CH2)n-1SO-3 Na+, CnSNa] (n = 5-9, 11) in mixtures with heavy water were measured by the PGSE-NMR technique at 25 degrees C. A slope change in the experimental trends permits the determination of the critical micelle concentration (CMC). In the micellar composition range, solubilized TMS molecules were used to determine the micelle intradiffusion coefficient, from which the micelle radii were obtained. Both the monomer surfactant and the micelle intradiffusion coefficients show a sharp decrease above the CMC. These results can be interpreted in terms of the obstruction effect due to the micelles. The electrostatic repulsion among charged particles strongly enhances this effect. A simple approach that permits the computation of the Gouy-Chapman layer thickness from the experimental coefficients has been proposed and the results are briefly discussed. Copyright 1999 Academic Press.

Crystal structure of a new alpha-cyclodextrin hydrate form. Molecular geometry and packing features: disordered solvent contribution

The crystallographic study of a new hydrated form of alpha-cyclodextrin (cyclohexaamylose) is reported. C36H60O30 . 11H2O; space group P2(1)2(1)2(1) with cell constants a = 13.839(3), b = 15.398(3), c = 24.209(7) A; final discrepancy index R = 0.057 for the 5182 observed reflections and 632 refined parameters. Besides four ordered water molecules placed outside alpha-cyclodextrins, the structure shows regions of severely disordered solvent mainly confined in the oligosaccharide cavities. The contribution of the observed disorder has been computed via Fourier inversions of the residual electron density and incorporated into the structure factors in further refinements of the ordered part. The alpha-cyclodextrin molecule assumes a relaxed round shape stabilised by a ring sequence of all the six possible O2 ... O3 intramolecular hydrogen bonds. The four ordered water molecules take part in an extensive network of hydrogen bonds (infinite chains and loops) without modifying the scheme of intramolecular H-bonds or the (-)gauche conformation of O-6-H hydroxyl groups. The structure shows a new molecular arrangement, for an "empty" hydrated alpha-cyclodextrin, like that "brick-type" observed for alpha-CD in the iodoanilide trihydrate complex crystallising in an isomorphous cell.

Microcalorimetric Study of Some Short-Chain Nonionic Surfactants

Apparent enthalpies of mixing were measured for various surfactants of the general formula CH3-(CH2)n-1-(OCH2-CH2)mOH(CnEm) in aqueous solution at 25 degreesC. From the experimental data the enthalpies of micellization were obtained. The results are briefly discussed. Copyright 1998 Academic Press.

Validity of ultrasonography for postoperative monitoring in pediatric urology

PURPOSE

We studied the validity of ultrasonography for short-term followup in pediatric urology.

MATERIALS AND METHODS

The study group comprised 137 children (187 urinary tracts) undergoing surgery at our hospital for congenital urological pathology between February 1982 and July 1992. The study protocol designed to evaluate urinary tract dilation postoperatively and monitor its progress, included ultrasound at discharge from the hospital, and repeat ultrasound between days 20 and 30, and days 45 and 60. Diuretic renography or excretory urography was indicated when urinary tract dilatation showed no signs of regressing or had increased on 2 consecutive evaluations. Ultrasound of the urinary tract was done to evaluate variations in the grade of dilatation of the pelves, calices, infundibula and ureters, and grade of hydronephrosis.

RESULTS

Variations in the grade of dilatation of the infundibula and ureters were early sensitive indicators of the absence of obstruction. Using this protocol only 15 of the 187 urinary tracts (8%) corrected surgically needed further evaluation for suspected iatrogenic stenosis, including 3 with obstruction that required reoperation. No other cases of obstruction were detected during long-term followup.

CONCLUSIONS

A series of sonographic evaluations performed within a short period and the greater significance attributed to more specific parameters, such as grade of dilatation of the infundibula and ureters, make ultrasound a valid means of monitoring urological cases postoperatively.

Clinical outcome of fetal uropathy. II. Sensitivity of echography for prenatal detection of obstructive pathology

Among 8,579 neonates born between February 1, 1981 and March 31, 1987, and cleared by prenatal sonography for significant urinary tract abnormality 158 subsequently were hospitalized because of signs or symptoms of urinary tract disease, predominantly urinary tract infection. Evaluation of these 158 patients revealed 24 with vesicoureteral reflux, 7 with duplicated systems (2 of which showed reflux), 1 with the syndrome of Fraley, 1 with pyelectasis and 5 with mild hydronephrosis (3 secondary to reflux and 2 with diethylenetriaminepentaacetic acid renal scans considered to be nonobstructed). There was no incidence of significant obstructive uropathy that had been missed by the previous prenatal sonography and that surfaced subsequently to cause morbidity in this series. The principal disorder of the urinary tract that may fail prenatal investigation is vesicoureteral reflux.

Clinical outcome of fetal uropathy. I. Predictive value of prenatal echography positive for obstructive uropathy

Clinical followup was performed in 73 neonates with a prenatal echographic suspicion of uropathy. Of 42 patients with a prenatal suspicion of unilateral hydronephrosis only 15 had pathological obstruction and 2 had multicystic dysplastic kidneys. Among 10 infants with a prenatal suspicion of bilateral hydronephrosis only 1 had true bilateral obstruction and 2 had unilateral obstruction. In 2 patients hydroureteronephrosis seen on prenatal echography was due to massive bilateral vesicoureteral reflux. In this group there was also a multicystic dysplastic kidney and 1 patient with bilateral cystic dysplasia. There was a prenatal suspicion of cystic disease in 8 infants. Postnatally, diagnosis was multicystic dysplastic kidney in 2 patients and a simple renal cyst in 4. The remaining 2 neonates had obstructive uropathy. Finally, of 13 neonates with a prenatal suspicion of anatomical-echo-structural abnormalities a definitive abnormality could be established in only 8. The predictive value of prenatal echography positive for obstructive uropathy was 34.6%.

Epidemiology of urinary tract infections and vesico-ureteral reflux in children

The purpose of this study was to assess the incidence of symptomatic urinary tract infection (U.T.I.) and malformations, such as vesico-ureteral reflux (V.U.R.), in the Trieste area. Data were collected in the framework of a survey based on the application of a protocol on urinary infections between 1979 and 1983. The U.T.I. incidence was found to be 1.38% of the 0-14-year-old residents, with a higher frequency in females (2.36%) than in males (0.46%). As regards V.U.R., the incidence in the population studied turned out to be 0.25%, with a females/males ratio of 4:1. Striking differences in incidence data were observed according to the age of U.T.I. and V.U.R. diagnosis and to the infection level (cystitis or pyelonephritis). The incidence of renal scarring resulted to be extremely low, which can be ascribed to the early diagnosis in our cases.

Primary epithelial tumors of the bladder in children

Epithelial tumors of the bladder in children are extremely rare and recurrences are even more unusual. We report 3 cases of which 2 had recurrence. ABO(H) antigens were negative in 1 case and they were mildly positive in the other. Although the current opinion is that epithelial tumors in children are benign and single, with a low incidence of malignancy, 3 other pediatric cases of epithelial tumor recurrence have been reported in the literature. Therefore, we wish to emphasize the importance of long-term and careful followup of these patients, since further recurrences are possible.