Pyrophosphorolytic excision of nonobligate chain terminators by hepatitis C virus NS5B polymerase

Nonobligate chain terminators, such as 2'-C-methylated nucleotides, block RNA synthesis by the RNA-dependent RNA polymerase (RdRp) of hepatitis C virus (HCV). Previous studies with related viral polymerases have shown that classical chain terminators lacking the 3'-hydroxyl group can be excised in the presence of pyrophosphate (PP(i)), which is detrimental to the inhibitory activity of these compounds. Here we demonstrate that the HCV RdRp enzyme is capable of removing both obligate and clinically relevant nonobligate chain terminators. Pyrimidines are more efficiently excised than are purines. The presence of the next complementary templated nucleotide literally blocks the excision of obligate chain terminators through the formation of a dead-end complex (DEC). However, 2'-C-methylated CMP is still cleaved efficiently under these conditions. These findings show that a 2'-methylated primer terminus impedes nucleotide binding. The S282T mutation, associated with resistance to 2'-C-methylated nucleotides, does not affect the excision patterns. Thus, the decreased susceptibility to 2'-C-methylated nucleotides appears to be based solely on improved discrimination between the inhibitor and its natural counterpart. In conclusion, our data suggest that the phosphorolytic excision of nonobligate, pyrimidine-based chain terminators can diminish their potency. The templated nucleotide does not appear to provide protection from excision through DEC formation.     

A Comparison of Continuous and Interrupted Suturing in Laparoscopic Pyeloplasty

Background:

Laparoscopic pyeloplasty is one of the most common reconstructive procedures performed by urologists. Both continuous and interrupted sutures are being practiced for ureteropelvic anastomosis. The success rate and the complications associated with the suturing technique needs evaluation. We analyzed the results from of our patients who underwent laparoscopic pyeloplasty using both techniques.

Objective:

To review the outcome differences among patients undergoing laparoscopic pyeloplasty regarding suturing technique.

Materials and Methods:

All patients who underwent laparoscopic, transperitoneal dismembered pyeloplasty of the primary pelviureteric obstruction were analyzed. The primary outcome was successful pyeloplasty, as assessed by the resolution of symptoms and T½ <10 minutes. The secondary outcomes were the complication rate and the operative parameters. The difference in the parameters was assessed by Student t test analysis.

Results:

Of the 107 patients we studied, 65 had interrupted suturing and 42 had continuous suturing. The success rate was not significantly different among the 2 groups. The mean suturing time, postoperative drainage volume, postoperative hospital stay, and total cost of the procedure were significantly less in the continuous suturing group.

Conclusion:

The continuous suturing technique is preferred over the interrupted suturing technique for laparoscopic pyeloplasty because the success rates are equal and the postoperative stay, suturing time, drain output, and cost of the procedure are better.     

Laparoscopic ureterocystoplasty before kidney transplantation

PURPOSE: To describe the technique of total laparoscopic ureterocystoplasty. MATERIALS AND METHODS: Laparoscopic ureterocystoplasty was performed to optimize the bladder function before kidney transplantation in a 23-year-old man. This patient had undergone bilateral cutaneous ureterostomy with fulguration of a posterior urethral valve at the age of 11 months. He underwent open surgical removal of multiple renal stones at age 10. He progressed to chronic renal failure at the age of 20, at which time hemodialysis was initiated. Because of grade IV vesicoureteral reflux and a poorly compliant bladder, the patient underwent laparoscopic ureterocystoplasty. RESULTS: The patient's lower urinary tract symptoms improved, and a urodynamic study performed after 6 months revealed a compliant bladder. Subsequently, a right nephrectomy and a live-donor renal transplantation from his mother were performed. At 1-year follow-up, his renal parameters were within normal range, he does not have any significant residual urine or urinary symptoms. CONCLUSION: Laparoscopic ureterocystoplasty is an excellent option for a poorly compliant bladder, especially when a patient has had multiple open surgeries and is awaiting renal transplantation.     

Detection and molecular characterization of a canine norovirus

We identified a novel calicivirus in a pup with enteritis. The isolate was related genetically (90.1% aa identity in the capsid protein) to a lion norovirus strain.     

Dose measurements and calculations of small radiation fields for 9-MV x rays

Measurements of dose distribution for square fields with sizes ranging from 1 X 1 to 30 X 30 cm for a 9-MV x-ray beam from a Neptune 10 linear accelerator, manufactured by CGR, are reported. Special attention was paid to field sizes smaller than 4 X 4 cm, used in radiosurgery techniques. To express the dose-monitor units relationship, total, collimator, and phantom scatter correction factors were obtained by experimental measurements. A strong dependence of these factors on the smallest field sizes (less than 4 X 4 cm) was shown. Measurements of the maximum depth dose dmax, plotted as a function of field size, showed a maximum at about 5 X 5 cm, in good agreement with previous results. dmax was also measured for the smallest fields, demonstrating that the contaminating electron component of the x-ray beam was not responsible for the dmax shift. Analysis of the penumbra width of cross dose distributions, as a function of field sizes, allowed us to postulate that the dmax shift could be due to the phantom scattered photons, which in turn were generated by the collimator scattered photons. Newly derived tissue-maximum ratio and scatter-maximum ratio data were used for dose profile calculations of 2 X 2, 4 X 4, and 10 X 10 cm field sizes. The agreement between experimental and calculated data was found to be +/- 2% within the geometrical edges of the fields and +/- 6% outside of them. A dose profile from the isocenter of a 2 X 2 cm square field moving through a 360 degree rotation arc was obtained and compared with that from the center of a 125I shielded source, as measured by Ling. Advantages and problems relating to the use of x-ray beams from linear accelerators in radiosurgery are discussed.     

Seroepidemiology of human bocavirus defined using recombinant virus-like particles

BACKGROUND: Human bocavirus (HBoV) is a newly identified human parvovirus for which seroepidemiology and antigenic properties remain undefined. METHODS: The HBoV VP2 gene, expressed from a baculovirus vector, produced virus-like particles (VLPs), which were used to raise rabbit anti-HBoV antisera and to develop an enzyme-linked immunosorbent assay (ELISA). The VLP-based ELISA was used to screen for HBoV-specific immunoglobulin G antibodies in a convenience sample of 270 serum specimens, mostly from children, obtained at Yale-New Haven Hospital; 208 specimens were also screened for erythrovirus B19-specific antibodies by a B19 VLP-based ELISA. RESULTS: Immunofluorescence and ELISA showed that human parvoviruses HBoV and B19 are antigenically distinct. By the HBoV VLP-based ELISA, 91.8% and 63.6% of serum specimens from infants in the first and second months of life, respectively, were found to be seropositive, as were 45.4% from 3-month-old infants and 25.0% from 4-month-old infants. The percentages of HBoV-seropositive children increased to 40.7%-60.0% for children 5-47 months of age and to >85% for individuals >or=48 months old. However, the overall percentage of B19-seropositive individuals was <40.5% for all age groups screened. CONCLUSIONS: HBoV infection is common during childhood, but a minority of children and young adults screened have evidence of B19 infection.     

Intracavitary dosimetry of a high-activity remote loading device with oscillating source

Dosimetric experiments have been carried out in order to obtain the dose distribution in water around a Fletcher applicator loaded by a Buchler system containing two 137Cs 148 GBq (4 Ci) sources and one 192Ir 740 GBq (20 Ci) source. The mechanical system which controls the movement of the 192Ir source and the resulting motion of the source are described. The dose distribution around the sources was measured photographically and by a PWT Normal 0.22 cm3 ionisation chamber. The absolute dose rate was measured along the lateral axes of the sources. The measurements of exposure in water near the sources were corrected for the effect due to the finite volume of the chamber. The "quantisation method" described by Cassell (1983) was utilised to calculate the variation of the dose rate along the lateral axes of the sources. The dose distribution around both 192Ir and 137Cs sources was found to be spherical for angles greater than 40 degrees from the longitudinal axes of the sources. A simple algorithm fitting the data for the moving 192Ir source is proposed. A program written in FORTRAN IV and run on a Univac 1100/80 computer has been used to plot dose distributions on anatomical data obtained from CT images. The uncertainties of the measurements and calculations have been examined and the greatest error has been found to be 5.5%. The clinical significance of the treatment method is discussed.     

Laparoscopic pyeloureterostomy: experience in three cases

PURPOSE: To report our experience with transperitoneal laparoscopic pyeloureterostomy for duplication of the collecting system. PATIENTS AND METHODS: Since January 2003, two adult patients with incomplete duplication of ureter with ureteropelvic junction obstruction of the lower moiety and a 4-month-old male baby with complete duplication of the ureter with reflux in the lower moiety underwent transperitoneal laparoscopic pyeloureterostomy. The baby also had excision of the lower-moiety ureter. RESULTS: There was no significant intraoperative or postoperative morbidity. Follow-up imaging revealed good drainage. CONCLUSION: With increasing experience in laparoscopic reconstructive urologic procedures, laparoscopic pyeloureterostomy is a feasible option, even in infants.